Inductive charging (also known as "wireless charging") uses an electromagnetic field to transfer

energy between two objects. This is usually done with a charging station. Energy is sent through

an inductive coupling to an electrical device, which can then use that energy to charge batteries or run

the device.

Induction chargers typically use an induction coil to create an alternating electromagnetic field from

within a charging base station, and a second induction coil in the portable device takes power from

the electromagnetic field and converts it back into electrical current to charge the battery. The two

induction coils in proximity combine to form an electrical transformer.[1][2]

Greater distances between sender and receiver coils can be achieved when the inductive charging

system usesresonant inductive coupling.

Contents

  [hide]

1   Advantages

2   Disadvantages

3   Examples

4   Electric vehicles

5   See also

6   References

7   External links

[edit]Advantages

Lower risk of electrical shock or shorting out when wet because there are no exposed conductors,

for example toothbrushes and shavers, or outdoors.

Protected connections - no corrosion when the electronics are all enclosed, away from water or

oxygen in the atmosphere.

Safer for medical implants - for embedded medical devices, allows

recharging/powering through the skin rather than having wires penetrate the skin, which would

increase the risk of infection.

Convenience - rather than having to connect a power cable, the device can be placed on or close

to a charge plate or stand.[3][4]

[edit]Disadvantages

Lower efficiency, waste heat - The main disadvantages of inductive charging are its lower

efficiency[citation needed] and increased resistive heating in comparison to direct contact.

Implementations using lower frequencies or older drive technologies charge more slowly and

generate heat within most portable electronics.[citation needed]

More costly - Inductive charging also requires drive electronics and coils in both device and

charger, increasing the complexity and cost of manufacturing.[1][2]

Slower charging - due to the lower efficiency, devices can take longer to charge when supplied

power is equal.

Inconvenience - When a mobile device is connected to a cable, it can be freely moved around

and operated while charging. In some implementations of inductive charging (such as the Qi

standard), the mobile device must be left on a pad, and thus can't be moved around or easily

operated while charging.

Incompatibility - Unlike (for example) a standardized MicroUSB charging connector, there are

no de facto standards, potentially leaving a consumer, organization or manufacturer with

redundant equipment when a standard emerges.

Newer approaches reduce transfer losses through the use of ultra thin coils, higher frequencies, and

optimized drive electronics. This results in more efficient and compact chargers and receivers,

facilitating their integration into mobile devices or batteries with minimal changes required.[3][5] These

technologies provide charging times comparable to wired approaches, and they are rapidly finding

their way into mobile devices.

For example, the Magne Charge vehicle recharger system employed high-frequency induction to

deliver high power at an efficiency of 86% (6.6 kW power delivery from a 7.68 kW power draw).[6]

[edit]Examples

The inventor of wireless energy transfer was Nikola Tesla.

An early example of inductive power transfer is the crystal radio which used the power of the

radio signal itself to power headphones. Some such radios can even use the power of a stronger

station to increase the volume of a weaker station

Transcutaneous energy transfer  (TET) systems in artificial hearts and other surgically implanted

devices.

Oral-B  rechargeable toothbrushes by the Braun company have used inductive charging since the

early 1990s.

Hughes Electronics  developed the Magne Charge interface for General Motors. The General

Motors EV1 electric car was charged by inserting an inductive charging paddle into a receptacle

on the vehicle. General Motors and Toyota agreed on this interface and it was also used in

the Chevrolet S-10 EV and Toyota RAV4 EV vehicles.

In 2006, researchers at the Massachusetts Institute of Technology reported that they had

discovered an efficient way to transfer power between coils separated by a few meters. The

team, led by Marin Soljačić, theorized that they could extend the distance between the coils by

adding resonance to the equation. The MIT wireless power project, called WiTricity, uses a

curved coil and capacitive plates.[7][8]

At CES in January 2007, Visteon unveiled their wireless charging system for in vehicle use that

could charge anything from cell phones to mp3 players.[9]

April 28, 2009: An Energizer inductive charging station for the Wii remote is reported on IGN.[10]

At CES in January 2009, Palm, Inc. announced their new Pre smartphone would be available with

an optional inductive charger accessory, the "Touchstone". The charger came with a required

special backplate that became standard on the subsequent Pre Plus model announced

at CES 2010. This was also featured on later Pixi, Pixi Plus, and Veer 4G smartphones. Upon

launch in 2011, the ill-fated HP Touchpad tablet (after HP's acquisition of Palm Inc.) had a built in

touchstone coil that doubled as an antenna for their NFC-like Touch to Share feature .[3][11][12]

In August 2009, a consortium of interested companies called the Wireless Power

Consortium announced they were nearing completion for a new industry standard for low-power

Inductive charging called Qi [13]

Intel and Samsung plan to launch Qi wireless charging devices for phones and laptops in 2013.[14]

Nokia  launched two smartphones (the Lumia 820 and Lumia 920) on 5 September 2012, which

feature Qi wireless charging.[15]

Google  and LG launched Nexus 4 which supports inductive charging using the Qi standard.

On November 21, 2012 HTC launched the United States' first 1080p phone, the Droid DNA,

for Verizon Wireless which also supported the Qi standard.

[edit]Electric vehicles

Main article: Electric vehicle

As mentioned above, Magne Charge inductive charging was employed by several types of electric

vehicles around 1998, but was discontinued[16] after the California Air Resources Board selected

the SAE J1772-2001, or "Avcon", conductive charging interface[17] for electric vehicles in California in

June 2001.[18]

In 2009, Evatran, a subsidiary of MTC Transformers, formally began development of Plugless Power,

an inductive charging system they claim is the world’s first hands-free, plugless, proximity charging

system for Electric Vehicles.[19] With the participation of the local municipality and several businesses,

field trials were begun in March 2010, on the system scheduled to be available in fourth quarter 2010.[4][20]

Researchers at the Korea Advanced Institute of Science and Technology (KAIST) have developed an

electric transport system (called Online Electric Vehicle, OLEV) where the vehicles get their power

needs from cables underneath the surface of the road via non-contact magnetic charging, (where a

power source is placed underneath the road surface and power is wirelessly picked up on the vehicle

itself. As a possible solution to traffic congestion and to improve overall efficiency by minimizing air

resistance and so reduce energy consumption, the test vehicles followed the power track in

a convoy formation. In July 2009, the researchers successfully supplied up to 60% power to a bus

over a gap of 12 cm.[21]

In one inductive charging system, one winding is attached to the underside of the car, and the other

stays on the floor of the garage.[22]

The major advantage of the inductive approach for vehicle charging is that there is no possibility

of electric shock as there are no exposed conductors, although interlocks, special connectors

andRCDs (ground fault interruptors - GFI) can make conductive coupling nearly as safe. An inductive

charging proponent from Toyota contended in 1998 that overall cost differences were minimal, while a

conductive charging proponent from Ford contended that conductive charging was more cost efficient.[23]

In 2010 onwards, car makers are signalling their interest in wireless charging as another piece of the

digital cockpit. A group was launched in May 2010 by the Consumer Electronics Associationto set a

baseline for interoperability for chargers. In one sign of the road ahead a General Motors executive is

chairing the standards effort group. Toyota and Ford managers said they also are interested in the

technology and the standards effort.[24]

Daimler’s Head of Future Mobility, Professor Herbert Kohler, however have expressed caution and

said the inductive charging for EVs is at least 15 years away and the safety aspects of inductive

charging for EVs have yet to be looked into in greater detail. For example, what would happen if

someone with a pacemaker is inside the vehicle? Another downside is that the technology requires a

precise alignment between the battery and the charging facility.[25]

In November 2011, the Mayor of London, Boris Johnson, and Qualcomm announced a trial of 13

wireless charging points and 50 EVs in the Shoreditch area of London's Tech City, due to be rolled

out in early 2012.[26][27]

Researchers in Korea are working on an electric bus powered by a continuous inductive connection

with a cable buried in the road.[28]

Wireless powerFrom Wikipedia, the free encyclopedia

  (Redirected from Wireless energy transfer)

Wireless power or wireless energy transmission is the transmission of electrical energy from a power

source to an electrical load without man-made conductors. Wireless transmission is useful in cases where

interconnecting wires are inconvenient, hazardous, or impossible. The problem of wireless power

transmission differs from that of wireless telecommunications, such as radio. In the latter, the proportion

of energy received becomes critical only if it is too low for the signal to be distinguished from the

background noise.[1]  With wireless power, efficiency is the more significant parameter. A large part of the

energy sent out by the generating plant must arrive at the receiver or receivers to make the system

economical.

The most common form of wireless power transmission is carried out using direct induction followed

by resonant magnetic induction. Other methods under consideration are electromagnetic radiation in the

form of microwaves or lasers [2]  and electrical conduction through natural media.[3]

Contents

  [hide]

1  Electric energy transfer

o 1.1  Electromagnetic induction

1.1.1  Electrodynamic induction method

1.1.2  Electrostatic induction method

o 1.2  Electromagnetic radiation

1.2.1  Beamed power, size, distance, and efficiency

1.2.2  Microwave method

1.2.3  Laser method

o 1.3  Electrical conduction

1.3.1  Disturbed charge of ground and air method

1.3.1.1  Terrestrial transmission line with atmospheric return

1.3.1.2  Terrestrial single-conductor surface wave transmission line

2  Timeline of wireless power

3  See also

4  Further reading

5  References

6  External links

[edit]Electric energy transfer

Main article: Coupling (electronics)

An electric current flowing through a conductor, such as a wire, carries electrical energy.  When an electric

current passes through a circuit there is an electric field in the dielectric surrounding the conductor;

magnetic field lines around the conductor and lines of electric force radially about the conductor.[4]

In a direct current circuit, if the current is continuous, the fields are constant; there is a condition of stress in

the space surrounding the conductor, which represents stored electric and magnetic energy, just as a

compressed spring or a moving mass represents stored energy. In an alternating current circuit, the fields

also alternate; that is, with every half wave of current and of voltage, the magnetic and the electric field

start at the conductor and run outwards into space with the speed of light.[5] Where these alternating fields

impinge on another conductor a voltage and a current are induced.[4]

Any change in the electrical conditions of the circuit, whether internal[6] or external[7] involves a readjustment

of the stored magnetic and electric field energy of the circuit, that is, a so-calledtransient. A transient is of

the general character of a condenser discharge through an inductive circuit. The phenomenon of the

condenser discharge through an inductive circuit therefore is of the greatest importance to the engineer, as

the foremost cause of high-voltage and high-frequency troubles in electric circuits.[8]

Electromagnetic induction is proportional to the intensity of the current and voltage in the conductor which

produces the fields and to the frequency. The higher the frequency the more intense the induction effect.

Energy is transferred from a conductor that produces the fields (the primary) to any conductor on which the

fields impinge (the secondary). Part of the energy of the primary conductor passes inductively across space

into secondary conductor and the energy decreases rapidly along the primary conductor. A high frequency

current does not pass for long distances along a conductor but rapidly transfers its energy by induction to

adjacent conductors. Higher induction resulting from the higher frequency is the explanation of the

apparent difference in the propagation of high frequency disturbances from the propagation of the low

frequency power of alternating current systems. The higher the frequency the more preponderant become

the inductive effects that transfer energy from circuit to circuit across space. The more rapidly the energy

decreases and the current dies out along the circuit, the more local is the phenomenon.[4]

The flow of electric energy thus comprises phenomena inside the conductor[9] and phenomena in the space

outside the conductor—the electric field—which, in a continuous current circuit, is a condition of steady

magnetic and dielectric stress, and in an alternating current circuit is alternating, that is, an electric wave

launched by the conductor[4] to become far-field electromagnetic radiation traveling through space with the

speed of light.

In electric power transmission and distribution, the phenomena inside the conductor are of main

importance, and the electric field of the conductor is usually observed only incidentally.[10]Inversely, in the

use of electric power for radio telecommunications it is only the electric and magnetic fields outside of the

conductor, that is far-field electromagnetic radiation, which is of importance in transmitting the message.

The phenomenon in the conductor, the current in the launching structure, is not used.[4]

The electric charge displacement in the conductor produces a magnetic field and resultant lines of electric

force. The magnetic field is a maximum in the direction concentric, or approximately so, to the conductor.

That is, a ferromagnetic body[11] tends to set itself in a direction at right angles to the conductor. The electric

field has a maximum in a direction radial, or approximately so, to the conductor. The electric field

component tends in a direction radial to the conductor and dielectric bodies may be attracted or repelled

radially to the conductor.[12]

The electric field of a circuit over which energy flows has three main axes at right angles with each other:

1. The magnetic field, concentric with the conductor.

2. The lines of electric force, radial to the conductor.

3. The power gradient, parallel to the conductor.

Where the electric circuit consists of several conductors, the electric fields of the conductors superimpose

upon each other, and the resultant magnetic field lines and lines of electric force are not concentric and

radial respectively, except approximately in the immediate neighborhood of the conductor. Between parallel

conductors they are conjugate of circles.  Neither the power consumption in the conductor, nor the

magnetic field, nor the electric field, are proportional to the flow of energy through the circuit. However, the

product of the intensity of the magnetic field and the intensity of the electric field is proportional to the flow

of energy or the power, and the power is therefore resolved into a product of the two components i and e,

which are chosen proportional respectively to the intensity of the magnetic field and of the electric field. The

component called the current is defined as that factor of the electric power which is proportional to the

magnetic field, and the other component, called the voltage, is defined as that factor of the electric power

which is proportional to the electric field.[12]

In radio telecommunications the electric field of the transmit antenna propagates through space as a radio

wave and impinges upon the receive antenna where it is observed by its magnetic and electric effect.

[12] Radio waves, microwaves, infrared radiation, visible light, ultraviolet radiation, X rays and gamma rays

are shown to be the same electromagnetic radiation phenomenon, differing one from the other only in

frequency of vibration.[4][13]

[edit]Electromagnetic induction

Energy transfer by electromagnetic induction is typically magnetic but capacitive coupling can also be

achieved.

[edit]Electrodynamic induction method

Main articles: Inductive coupling, Electrodynamic induction, and Resonant inductive coupling

The electrodynamic induction wireless transmission technique is near field over distances up to about one-

sixth of the wavelength used. Near field energy itself is non-radiative but some radiative losses do occur. In

addition there are usually resistive losses. With electrodynamic induction, electric current flowing through

a primary coil creates a magnetic field that acts on a secondary coil producing a current within it. Coupling

must be tight in order to achieve high efficiency. As the distance from the primary is increased, more and

more of the magnetic field misses the secondary.  Even over a relatively short range the inductive coupling

is grossly inefficient, wasting much of the transmitted energy.[14]

This action of an electrical transformer is the simplest form of wireless power transmission. The primary

and secondary circuits of a transformer are not directly connected. Energy transfer takes place through a

process known as mutual induction. Principal functions are stepping the primary voltage either up or down

and electrical isolation. Mobile phone and electric toothbrush battery chargers, and electrical power

distribution transformers are examples of how this principle is used. Induction cookers use this method.

The main drawback to this basic form of wireless transmission is short range. The receiver must be directly

adjacent to the transmitter or induction unit in order to efficiently couple with it.

The application of resonance increases the transmission range somewhat. When resonant coupling is

used, the transmitter and receiver inductors are tuned to the same natural frequency. Performance can be

further improved by modifying the drive current from a sinusoidal to a nonsinusoidal transient waveform.

[15] In this way significant power may be transmitted between two mutually-attuned LC circuits having a

relatively low coefficient of coupling. Transmitting and receiving coils are usually single layer solenoids or

flat spirals with series capacitors, which, in combination, allow the receiving element to be tuned to the

transmitter frequency.

Common uses of resonance-enhanced electrodynamic induction are charging the batteries of portable

devices such as laptop computers and cell phones, medical implants and electric vehicles.[16][17][18] A

localized charging technique[19] selects the appropriate transmitting coil in a multilayer winding array

structure.[20] Resonance is used in both the wireless charging pad (the transmitter circuit) and the receiver

module (embedded in the load) to maximize energy transfer efficiency. This approach is suitable for

universal wireless charging pads for portable electronics such as mobile phones. It has been adopted as

part of the Qi wireless charging standard.

It is also used for powering devices having no batteries, such as RFID patches and contactless smartcards,

and to couple electrical energy from the primary inductor to the helical resonator ofTesla coil wireless

power transmitters.

[edit]Electrostatic induction method

Main article: Capacitive coupling

The illumination of two exhausted tubes by means of a powerful, rapidly alternating electrostatic field created between

two vertical metal sheets suspended from the ceiling on insulating cords.  This involves the physics of electrostatic

induction.[21][22][23]

Electrostatic induction or capacitive coupling is the passage of electrical energy through a dielectric. In

practice it is an electric field gradient ordifferential capacitance between two or more insulated terminals,

plates, electrodes, or nodes that are elevated over a conducting ground plane. The electric field is created

by charging the plates with a high potential, high frequency alternating current power supply. The

capacitance between two elevated terminals and a powered device form a voltage divider.

The electric energy transmitted by means of electrostatic induction can be utilized by a receiving device,

such as a wireless lamp.[24][25][26] Teslademonstrated the illumination of wireless lamps by energy that was

coupled to them through an alternating electric field.[21][27][28]

"Instead of depending on electrodynamic induction at a distance to light the tube . . . [the] ideal way of

lighting a hall or room would . . . be to produce such a condition in it that an illuminating device could be

moved and put anywhere, and that it is lighted, no matter where it is put and without being electrically

connected to anything. I have been able to produce such a condition by creating in the room a

powerful, rapidly alternating electrostatic field. For this purpose I suspend a sheet of metal a distance from

the ceiling on insulating cords and connect it to one terminal of the induction coil, the other terminal being

preferably connected to the ground. Or else I suspend two sheets . . . each sheet being connected with one

of the terminals of the coil, and their size being carefully determined. An exhausted tube may then be

carried in the hand anywhere between the sheets or placed anywhere, even a certain distance beyond

them; it remains always luminous."[29]

The principle of electrostatic induction is applicable to the electrical conduction wireless transmission

method.

“In some cases when small amounts of energy are required the high elevation of the terminals, and more

particularly of the receiving-terminal D', may not be necessary, since, especially when the frequency of the

currents is very high, a sufficient amount of energy may be collected at that terminal by electrostatic

induction from the upper air strata, which are rendered conducting by the active terminal of the transmitter

or through which the currents from the same are conveyed."[30]

[edit]Electromagnetic radiation

Far field methods achieve longer ranges, often multiple kilometer ranges, where the distance is much

greater than the diameter of the device(s). The main reason for longer ranges with radio wave and optical

devices is the fact that electromagnetic radiation in the far-field can be made to match the shape of the

receiving area (using high directivity antennas or well-collimated laser beam) thereby delivering almost all

emitted power at long ranges. The maximum directivity for antennas is physically limited by diffraction.

[edit]Beamed power, size, distance, and efficiency

The dimensions of the components may be dictated by the distance from transmitter to receiver,

the wavelength and the Rayleigh criterion or diffraction limit, used in standard radio

frequency antenna  design, which also applies to lasers. In addition to the Rayleigh criterion Airy's diffraction

limit is also frequently used to determine an approximate spot size at an arbitrary distance from

the aperture.

The Rayleigh criterion dictates that any radio wave, microwave or laser beam will spread and become

weaker and diffuse over distance; the larger the transmitter antenna or laser aperture compared to

the wavelength of radiation, the tighter the beam and the less it will spread as a function of distance (and

vice versa). Smaller antennae also suffer from excessive losses due to side lobes. However, the concept

of laser aperture considerably differs from an antenna. Typically, a laser aperture much larger than the

wavelength induces multi-moded radiation and mostlycollimators are used before emitted radiation couples

into a fiber or into space.

Ultimately, beamwidth is physically determined by diffraction due to the dish size in relation to the

wavelength of the electromagnetic radiation used to make the beam. Microwave power beaming can be

more efficient than lasers, and is less prone to atmospheric attenuation caused by dust or water

vapor losing atmosphere to vaporize the water in contact.

Then the power levels are calculated by combining the above parameters together, and adding in

the gains and losses due to the antenna characteristics and the transparency anddispersion[disambiguation

needed] of the medium through which the radiation passes. That process is known as calculating a link

budget.

[edit]Microwave method

Main article: Microwave power transmission

An artist's depiction of a solar satellitethat could send electric energy by microwaves to a space vessel or planetary

surface.

Power transmission via radio waves can be made more directional, allowing longer distance power

beaming, with shorter wavelengths of electromagnetic radiation, typically in the microwave range.

A rectenna may be used to convert the microwave energy back into electricity. Rectenna conversion

efficiencies exceeding 95% have been realized. Power beaming using microwaves has been proposed for

the transmission of energy from orbiting solar power satellites to Earth and the beaming of power to

spacecraft leaving orbit has been considered.[2][31]

Power beaming by microwaves has the difficulty that for most space applications the required aperture

sizes are very large due to diffraction limiting antenna directionality. For example, the 1978 NASA Study of

solar power satellites required a 1-km diameter transmitting antenna, and a 10 km diameter receiving

rectenna, for a microwave beam at 2.45 GHz.[32] These sizes can be somewhat decreased by using shorter

wavelengths, although short wavelengths may have difficulties with atmospheric absorption and beam

blockage by rain or water droplets. Because of the "thinned array curse," it is not possible to make a

narrower beam by combining the beams of several smaller satellites.

For earthbound applications a large area 10 km diameter receiving array allows large total power levels to

be used while operating at the low power density suggested for human electromagnetic exposure safety. A

human safe power density of 1 mW/cm2 distributed across a 10 km diameter area corresponds to 750

megawatts total power level. This is the power level found in many modern electric power plants.

Following World War II, which saw the development of high-power microwave emitters known as cavity

magnetrons, the idea of using microwaves to transmit power was researched. By 1964 a miniature

helicopter propelled by microwave power had been demonstrated.[33]

Japanese researcher Hidetsugu Yagi also investigated wireless energy transmission using a directional

array antenna that he designed. In February 1926, Yagi and Uda published their first paper on the tuned

high-gain directional array now known as the Yagi antenna. While it did not prove to be particularly useful

for power transmission, this beam antenna has been widely adopted throughout the broadcasting and

wireless telecommunications industries due to its excellent performance characteristics.[34]

Wireless high power transmission using microwaves is well proven. Experiments in the tens of kilowatts

have been performed at Goldstone in California in 1975[35][36][37] and more recently (1997) at Grand Bassin

on Reunion Island.[38] These methods achieve distances on the order of a kilometer.

[edit]Laser method

With a laser beam centered on its panel of photovoltaic cells, a lightweight model plane makes the first flight of an

aircraft powered by a laser beam inside a building at NASA Marshall Space Flight Center.

In the case of electromagnetic radiation closer to visible region of spectrum (10s of microns (um) to 10s

of nm), power can be transmitted by converting electricity into a laser beam that is then pointed at a solar

cell receiver[39] This mechanism is generally known as "power beaming" because the power is beamed at a

receiver that can convert it to usable electrical energy.

Advantages of laser based energy transfer compared with other wireless methods are:[40]

1. collimated  monochromatic wavefront propagation allows narrow beam cross-section area for

energy transmission over large ranges.

2. compact size of solid state lasers-photovoltaics semiconductor diodes fit into small products.

3. no radio-frequency interference to existing radio communication such as Wi-Fi and cell phones.

4. control of access; only receivers illuminated by the laser receive power.

Its drawbacks are:

1. Laser radiation is hazardous, even at low power levels it can blind people and animals, and at high

power levels it can kill through localized spot heating

2. Conversion to light, such as with a laser, is inefficient

3. Conversion back into electricity is inefficient, with photovoltaic cells achieving 40%–50% efficiency.

[41] (Note that conversion efficiency is rather higher with monochromatic light than with insolation of

solar panels).

4. Atmospheric absorption, and absorption and scattering by clouds, fog, rain, etc., causes losses,

which can be as high as 100% loss

5. As with microwave beaming, this method requires a direct line of sight with the target.

The laser "powerbeaming" technology has been mostly explored in military weapons [42] [43]

[44] and aerospace [45] [46]  applications and is now being developed for commercial and consumer

electronics Low-Power applications. Wireless energy transfer system using laser for consumer space has

to satisfy Laser safety requirements standardized under IEC 60825.

To develop an understanding of the trade-offs of Laser ("a special type of light wave"-based system):

1. Propagation of a laser beam [47] [48] [49]  (on how Laser beam propagation is much less affected by

diffraction limits)

2. Coherence and the range limitation problem  (on how spatial and spectral coherence

characteristics of Lasers allows better distance-to-power capabilities[50])

3. Airy disk  (on how wavelength fundamentally dictates the size of a disk with distance)

4. Applications of laser diodes  (on how the laser sources are utilized in various industries and their

sizes are reducing for better integration)

Geoffrey Landis [51] [52] [53]  is one of the pioneers of solar power satellite [54]  and laser-based transfer of energy

especially for space and lunar missions. The continuously increasing demand for safe and frequent space

missions has resulted in serious thoughts on a futuristic space elevator [55] [56]  that would be powered by

lasers. NASA's space elevator would need wireless power to be beamed to it for it to climb a tether.[57]

NASA's Dryden Flight Research Center has demonstrated flight of a lightweight unmanned model plane

powered by a laser beam.[58] This proof-of-concept demonstrates the feasibility of periodic recharging using

the laser beam system and the lack of need to return to ground.

[edit]Electrical conduction

The Tesla coil wireless transmitter

U.S. Patent 1,119,732

Means for long conductors of electricity forming part of an electric circuit and electrically connecting said ionized beam

to an electric circuit. Hettinger 1917 -(U.S. Patent 1,309,031)

Main article: World Wireless System

[edit]Disturbed charge of ground and air method

The wireless transmission of alternating current electricity through the earth with an equivalent electrical

displacement through the air above it achieves long ranges that are superior to the resonant electrical

induction methods and favorably comparable to the electromagnetic radiation methods.[59]  Electrical energy

can be transmitted through inhomogeneous Earth with low loss because the net resistance between earth

antipodes is less than 1 ohm.[3]  The electrical displacement takes place predominantly by electrical

conduction through the oceans, and metallic ore bodies and similar subsurface structures.  The electrical

displacement is also by means of electrostatic induction through the more dielectric regions such as quartz

deposits and other non-conducting minerals.[60][61]  Receivers are energized by currents through the earth

while an equivalent electric displacement occurs in the atmosphere.[62]

This energy transfer technique is suitable for transmission of electrical power in industrial quantities and

also for wireless broadband telecommunications.  The Wardenclyffe Tower project was an early

commercial venture for trans-Atlantic wireless telephony and proof-of-concept demonstrations of global

wireless power transmission using this method.[63] The facility was not completed due to insufficient funding.

[64]

[edit]Terrestrial transmission line with atmospheric return

Single wire with Earth return electrical power transmission systems rely on current flowing through the

earth plus a single wire insulated from the earth to complete the circuit. In emergencies high-voltage direct

current power transmission systems can also operate in the 'single wire with earth return' mode. Elimination

of the raised insulated wire, and transmission of high-potential alternating current through the earth with an

atmospheric return circuit is the basis of this method of wireless electrical power transmission.

The atmospheric conduction method depends upon the passage of electrical current through the earth, and

through the upper troposphere and thestratosphere.[65]  Current flow is induced by electrostatic induction up

to an elevation of approximately 3 miles (4.8 km) above Earth's surface.[66][67]Electrical conduction and the

flow of current through the upper atmospheric strata starting at a barometric pressure of approximately 130

millimeters of mercury is made possible by the creation of capacitively coupled discharge plasma through

the process of atmospheric ionization.[68][69][70] In this way electric lamps can be lit and electric motors turned

at moderate distances. The transmitted energy can be detected at much greater distances.[71]

A global system for "the transmission of electrical energy without wires" called the World Wireless System,

dependent upon the high electrical conductivity of plasma and the high electrical conductivity of the earth,

was proposed as early as 1904.[72][73]

[edit]Terrestrial single-conductor surface wave transmission line

Main article: Single-wire transmission line

The basic transmitter used for the terrestrial single-conductor earth resonance method is identical to that

used for the atmospheric conduction method.[74][75]

Observations have been made that may be inconsistent with a basic tenet of physics related to the scalar

derivatives of the electromagnetic potentials[76][77][78][79][80][81][82] that are presently considered to

be nonphysical.[83]

[edit]Timeline of wireless power

1826: André-Marie Ampère develops Ampère's circuital law showing that electric current produces a

magnetic field.[84]

1831: Michael Faraday develops Faraday's law of induction describing the electromagnetic force

induced in a conductor by a time-varying magnetic flux.

1836: Nicholas Callan invents the electrical transformer, also known as the induction coil.

1865: James Clerk Maxwell synthesizes the previous observations, experiments and equations of

electricity, magnetism and optics into a consistent theory and mathematically models the behavior

of electromagnetic radiation in a set of partial differential equations known as Maxwell's equations.

1888: Heinrich Rudolf Hertz confirms the existence of electromagnetic radiation. Hertz’s "apparatus for

generating electromagnetic waves" was a VHF or UHF "radio wave" spark gap transmitter.

1891: Tesla demonstrates wireless energy transmission by means of electrostatic induction using a

high-tension induction coil before the American Institute of Electrical Engineers at Columbia College.[85]

1893: Tesla demonstrates the wireless illumination of phosphorescent lamps of his design at

the World's Columbian Exposition in Chicago.[86]

1893: Tesla publicly demonstrates wireless power and proposes the wireless transmission of signals

before a meeting of the National Electric Light Association in St. Louis.[26][87][88][89]

1894: Tesla lights incandescent lamps wirelessly at the 35 South Fifth Avenue laboratory in New York

City by means of "electro-dynamic induction" or resonant inductive coupling.[90][91][92]

1894: Hutin & LeBlanc, espouse long held view that inductive energy transfer should be possible, they

received U.S. Patent 527,857 describing a system for power transmission at 3 kHz.[93]

1894: Jagdish Chandra Bose rings a bell at a distance using electromagnetic waves and also

ignites gunpowder, showing that communications signals can be sent without using wires.[94][95]

1895: Marconi demonstrates radio transmission over a distance of 1.5 miles.[89][96] Developed Marconi's

Law.

1896: Tesla demonstrates wireless transmission over a distance of about 48 kilometres (30 mi).[97]

1897: Tesla files his first patent application dealing specifically with wireless transmission.

1899: Tesla continues wireless power transmission research in Colorado Springs and writes, "the

inferiority of the induction method would appear immense as compared with the disturbed charge of

ground and air method."[98]

1902: Nikola Tesla vs. Reginald Fessenden – U.S. Patent Interference No. 21,701, System of

Signaling (wireless); wireless power transmission, time and frequency domain spread

spectrumtelecommunications, electronic logic gates in general.[99]

1904: At the St. Louis World's Fair, a prize is offered for a successful attempt to drive a

0.1 horsepower (75 W) airship motor by energy transmitted through space at a distance of at least 100

feet (30 m).[100]

1916: Tesla states, "In my [disturbed charge of ground and air] system, you should free yourself of the

idea that there is [electromagnetic] radiation, that energy is radiated. It is not radiated; it is

conserved."[101]

1917: The Wardenclyffe tower is demolished. . . .

1926: Shintaro Uda and Hidetsugu Yagi publish their first paper on Uda's "tuned high-gain directional

array"[34] better known as the Yagi antenna.

1961: William C. Brown publishes an article exploring possibilities of microwave power transmission.

[102][103]

1968: Peter Glaser proposes wirelessly transmitting solar energy captured in space using

"Powerbeaming" technology.[104][105] This is usually recognized as the first description of a solar power

satellite.

1973: The world's first passive RFID system is demonstrated at Los-Alamos National Lab.[106]

1975: Goldstone Deep Space Communications Complex does experiments in the tens of kilowatts.[35]

[36][37]

1998: RFID tags are powered by electrodynamic induction over a few feet.[citation needed]

1999: Prof. Shu Yuen (Ron) Hui and Mr. S.C. Tang file a patent on "Coreless Printed-Circuit-Board

(PCB) transformers and operating techniques", which form the basis for future planar charging surface

with "vertical flux" leaving the planar surface. The circuit uses resonant circuits for wireless power

transfer. EP(GB)0935263B

2000: Prof. Shu Yuen (Ron) Hui invent a planar wireless charging pad using the "vertical flux"

approach and resonant power transfer for charging portable consumer electronic products. A patent is

filed on "Apparatus and method of an inductive battery charger,” PCT Patent PCT/AU03/00 721, 2000.

2001 Prof. Shu Yuen (Ron) Hui and Dr. S.C. Tang file a patent on "Planar Printed-Circuit-Board

Transformers with Effective Electromagnetic Interference (EMI) Shielding". The EM shield consists of a

thin layer of ferrite and a thin layer of copper sheet. It enables the underneath of the future wireless

charging pads to be shielded with a thin EM shield structure with thickness of typically 0.7mm or

less. U.S. Patent 6,501,364.

2001: Prof. Ron Hui's team demonstrate that the coreless PCB transformer can transmit power close

to 100W in ‘A low-profile low-power converter with coreless PCB isolation transformer, IEEE

Transactions on Power Electronics, Volume: 16 Issue: 3 , May 2001. A team of Philips Research

Center Aachen, led by Dr. Eberhard Waffenschmidt, use it to power an 100W lighting device in their

paper "Size advantage of coreless transformers in the MHz range" in the European Power Electronics

Conference in Graz.

2002: Prof. Shu Yuen (Ron) Hui extends the planar wireless charging pad concept using the vertical

flux approach to incorporate free-positioning feature for multiple loads. This is achieved by using a

multilayer planar winding array structure. Patent were granted as "Planar Inductive Battery Charger",

GB2389720 and GB 2389767.[citation needed]

2005: Prof. Shu Yuen (Ron) Hui and Dr. W.C. Ho publish their work in the IEEE Transactions on a

planar wireless charging platform with free-positioning feature. The planar wireless charging pad is

able to charge several loads simultaneously on a flat surface.[citation needed]

2007: A localized charging technique is reported by Dr. Xun Liu and Prof. Ron Hui for the wireless

charging pad with free-positioning feature. With the aid of the double-layer EM shields enclosing the

transmitter and receiver coils, the localized charging selects the right transmitter coil so as to minimize

flux leakage and human exposure to radiation.[citation needed]

2007: Using electrodynamic induction the WiTricity physics research group, led by Prof. Marin

Soljacic at MIT, wirelessly power a 60W light bulb with 40% efficiency at a 2 metres (6.6 ft) distance

with two 60 cm-diameter coils.[107]

2008: Bombardier offers a new wireless power transmission product PRIMOVE, a system for use on

trams and light-rail vehicles.[108]

2008: Intel reproduces the original 1894 implementation of electrodynamic induction and Prof. John

Boys group's 1988 follow-up experiments by wirelessly powering a nearby light bulb with 75%

efficiency.[109]

2008: Greg Leyh and Mike Kennan of the Nevada Lightning Laboratory publish a paper on

the disturbed charge of ground and air method of wireless power transmission with circuit simulations

and test results showing an efficiency greater than can be obtained using the electrodynamic induction

method.[59]

2009: Palm (now a division of HP) launches the Palm Pre smartphone with the Palm

Touchstone wireless charger.

2009: A Consortium of interested companies called the Wireless Power Consortium announce they are

nearing completion for a new industry standard for low-power (which is eventually published in August

2010) inductive charging.[110]

2009: An Ex approved Torch and Charger aimed at the offshore market is introduced.[111] This product

is developed by Wireless Power & Communication, a Norway based company.

2009: A simple analytical electrical model of electrodynamic induction power transmission is proposed

and applied to a wireless power transfer system for implantable devices.[112]

2009: Lasermotive uses diode laser to win $900k NASA prize in power beaming, breaking several

world records in power and distance, by transmitting over a kilowatt more than several hundred

meters.[113]

2009: Sony shows a wireless electrodynamic-induction powered TV set, 60 W over 50 cm[114]

2010: Haier Group debuts “the world's first” completely wireless LCD television at CES 2010 based on

Prof. Marin Soljacic's follow-up research on the 1894 electrodynamic induction wireless energy

transmission method and the Wireless Home Digital Interface (WHDI).[115]

2010: System On Chip (SoC) group in University of British Columbia develops a highly efficient

wireless power transmission systems using 4-coils. The design is optimized for implantable

applications and power transfer efficiency of 82% is achieved.[116]

2012: "Bioelectromagnetics and Implantable Devices" group in University of Utah, USA develops an

efficient multi-Coil telemetry system for power and data transfer in biomedical Implants. Design

approach is extendable to other industrial "smart" wireless power transfer system. Proposed multi-coil

based telemetry system achieves more than twice power transfer efficiency and higher tunable

frequency bandwidth as compared to its equivalent two-coil design. Based on circuit theory, analytical

formulation is proposed to optimize the design for maximum power transfer, frequency bandwidth and

power transfer efficiency.[117]

2012: Christopher Tucker, Kevin Warwick and William Holderbaum of the University of Reading, UK

develop a highly-efficient, compact power transfer system safe for use in human proximity. The design

is simple and uses only a few components to generate stable currents for biomedical implants. It

resulted from research that directly attempted to extend Tesla’s 1897 wireless power work.[118]

Electromagnetic compatibilityFrom Wikipedia, the free encyclopedia

Anechoic RF chamber used for EMC testing (radiated emissions and immunity). The furniture has to be made of wood

or plastic, and not metal

LPDA antenna measurement for outdoor

Electromagnetic compatibility (EMC) is the branch of electrical sciences which studies the unintentional

generation, propagation and reception of electromagnetic energy with reference to the unwanted effects

(Electromagnetic interference, or EMI) that such energy may induce.

EMC aims to ensure that equipment items or systems will not interfere with or prevent each other's correct

operation through spurious emission and absorption of EMI. EMC is sometimes referred to as EMI Control,

and in practice EMC and EMI are frequently referred to as a combined term "EMC/EMI".

Contents

  [hide]

1  Introduction

2  Types of interference

o 2.1  Continuous interference

o 2.2  Pulse or transient interference

3  Coupling mechanisms

o 3.1  Conductive coupling

o 3.2  Inductive coupling

3.2.1  Capacitive coupling

3.2.2  Magnetic coupling

o 3.3  Radiative coupling

4  EMC control

o 4.1  Characterising the threat

o 4.2  Laws and regulators

4.2.1  Regulatory and standards bodies

4.2.2  Laws

o 4.3  EMC design

4.3.1  Grounding and shielding

4.3.2  Other general measures

4.3.3  Emissions suppression

4.3.4  Susceptibility hardening

o 4.4  EMC testing

4.4.1  Susceptibility testing

4.4.2  Emissions testing

5  History

6  EMC test equipment manufacturers (alphabetic)

7  See also

8  References

9  External links

o 9.1  Web sites

o 9.2  General introductions

o 9.3  Specific topics

[edit]Introduction

While electromagnetic interference (EMI) is a phenomenon - the radiation emitted and its effects -

electromagnetic compatibility (EMC) is an equipment characteristic or property - to not behave

unacceptably in the EMI environment.

EMC ensures the correct operation, in the same electromagnetic environment, of different equipment items

which use or respond to electromagnetic phenomena, and the avoidance of any interference effects.

Another way of saying this is that EMC is the control of EMI so that unwanted effects are prevented.

EMC divides into a number of issues:

EMI is the radiation emitted and its effects on the victim.

Emission is the unwanted generation of electromagnetic energy by some emitter or source.

Susceptibility or Immunity is the ability of the receptor or victim equipment to operate correctly in the

presence of electromagnetic disturbances. Susceptibility and immunity are opposites - an equipment

which has high susceptibility has low immunity, and vice versa.

Coupling is the mechanisms by which EMI is able to travel from source to victim.

Besides understanding the phenomena in themselves, EMC also addresses the countermeasures, such as

control regimes, design and measurement, which should be taken in order to prevent emissions from

causing any adverse effect.

[edit]Types of interference

Main article: Electromagnetic interference

Electromagnetic interference divides into several categories according to the source and signal

characteristics.

The origin of noise can be man made or natural.

[edit]Continuous interference

Continuous, or Continuous Wave (CW), interference arises where the source continuously emits at a given

range of frequencies. This type is naturally divided into sub-categories according to frequency range, and

as a whole is sometimes referred to as "DC to daylight".

Audio Frequency, from very low frequencies up to around 20 kHz. Frequencies up to 100 kHz may

sometimes be classified as Audio. Sources include:

Mains hum from; power supply units, nearby power supply wiring, transmission lines and

substations.

Audio processing equipment, such as audio power amplifiers and loudspeakers.

Demodulation of a high-frequency carrier wave such as an FM radio transmission.

Radio Frequency Interference (RFI), from typically 20 kHz to an upper limit which constantly increases

as technology pushes it higher. Sources include:

Wireless and Radio Frequency Transmissions

Television and Radio Receivers

Industrial, scientific and medical equipment (ISM)

Digital processing circuitry such as microcontrollers

Broadband noise may be spread across parts of either or both frequency ranges, with no particular

frequency accentuated. Sources include:

Solar Activity

Continuously operating spark gaps such as arc welders

CDMA  (spread-spectrum) mobile telephony

[edit]Pulse or transient interference

Electromagnetic Pulse, EMP, also sometimes called Transient disturbance, arises where the source emits

a short-duration pulse of energy. The energy is usually broadband by nature, although it often excites a

relatively narrow-band damped sine wave response in the victim.

Sources divide broadly into isolated and repetitive events.

Sources of isolated EMP events include:

Switching action of electrical circuitry, including inductive loads such as relays, solenoids, or

electric motors.

Electrostatic Discharge  (ESD), as a result of two charged objects coming into close proximity or

even contact.

Lightning  Electromagnetic Pulse (LEMP), although typically a short series of pulses.

Nuclear  Electromagnetic Pulse (NEMP), as a result of a nuclear explosion.

Non-Nuclear Electromagnetic Pulse (NNEMP) weapons.

Power Line  Surges/Pulses

Sources of repetitive EMP events, sometimes as regular pulse trains, include:

Electric Motors

Gasoline engine ignition systems

Continual switching actions of digital electronic circuitry.

[edit]Coupling mechanisms

Some of the technical words employed can be used with differing meanings. These terms are used here in

a widely accepted way, which is consistent with other articles in the encyclopedia.

The basic arrangement of noise source, coupling path and victim, receptor or sink is shown in the figure

below. Source and victim are usually electronic hardware devices, though the source may be a natural

phenomenon such as a lightning strike, electrostatic discharge (ESD) or, in one famous case, the Big

Bang at the origin of the Universe.

The four electromagnetic interference (EMI) coupling modes.

There are four basic coupling mechanisms: conductive, capacitive, magnetic or inductive, and radiative.

Any coupling path can be broken down into one or more of these coupling mechanisms working together.

For example the lower path in the diagram involves inductive, conductive and capacitive modes.

[edit]Conductive coupling

Conductive coupling occurs when the coupling path between the source and the receptor is formed by

direct contact with a conducting body, for example a transmission line, wire, cable, PCBtrace or metal

enclosure.

Conducted noise is also characterised by the way it appears on different conductors:

Common-mode or common-impedance[1] coupling: noise appears in phase (in the same direction)

on two conductors .

Differential-mode coupling: noise appears out of phase (in opposite directions) on two conductors .

[edit]Inductive coupling

Inductive coupling occurs where the source and receiver are separated by a short distance (typically less

than a wavelength). Strictly, "Inductive coupling" can be of two kinds, electrical induction and magnetic

induction. It is common to refer to electrical induction as capacitive coupling, and to magnetic induction

as inductive coupling.

[edit]Capacitive coupling

Capacitive coupling occurs when a varying electrical field exists between two adjacent conductors

typically less than a wavelength apart, inducing a change in voltage across the gap.

[edit]Magnetic coupling

Inductive coupling or magnetic coupling (MC) occurs when a varying magnetic field exists between two

parallel conductors typically less than a wavelength apart, inducing a change in voltagealong the receiving

conductor.

[edit]Radiative coupling

Radiative coupling or electromagnetic coupling occurs when source and victim are separated by a

large distance, typically more than a wavelength. Source and victim act as radio antennas: the source

emits or radiates an electromagnetic wave which propagates across the open space in between and is

picked up or received by the victim.

[edit]EMC control

The damaging effects of electromagnetic interference pose unacceptable risks in many areas of

technology, and it is necessary to control such interference and reduce the risks to acceptable levels.

The control of electromagnetic interference (EMI) and assurance of EMC comprises a series of related

disciplines:

Characterising the threat.

Setting standards for emission and susceptibility levels.

Design for standards compliance.

Testing for standards compliance.

For a complex or novel piece of equipment, this may require the production of a dedicated EMC control

plan summarizing the application of the above and specifying additional documents required.

[edit]Characterising the threat

Characterisation of the problem requires understanding of:

The interference source and signal.

The coupling path to the victim.

The nature of the victim both electrically and in terms of the significance of malfunction.

The risk posed by the threat is usually statistical in nature, so much of the work in threat characterisation

and standards setting is based on reducing the probability of disruptive EMI to an acceptable level, rather

than its assured elimination.

[edit]Laws and regulators

[edit]Regulatory and standards bodies

Main article: List of EMC directives

Several international organizations work to promote international co-operation on standardization

(harmonization), including publishing various EMC standards. Where possible, a standard developed by

one organization may be adopted with little or no change by others. This helps for example to harmonize

national standards across Europe. Standards organizations include:

International Electrotechnical Commission  (IEC), which has several committees working full-time on

EMC issues. These are:

Technical Committee 77 (TC77), working on electromagnetic compatibility between equipment

including networks.

Comité International Spécial des Perturbations Radioélectriques  (CISPR), or International Special

Committee on Radio Interference.

The Advisory Committee on Electromagnetic Compatibility (ACEC) co-ordinates the IEC's work on

EMC between these committees.

International Organization for Standardization  (ISO), which publishes standards for the automotive

industry.

Among the more well known national organizations are:

Europe:

Comité Européen de Normalisation  (CEN) or European Committee for Standardization).

Comité Européen de Normalisation Electrotechniques  (CENELEC) or European Committee for

Electrotechnical Standardisation.

European Telecommunications Standards Institute  (ETSI).

United States:

The Federal Communications Commission (FCC).

The Society of Automotive Engineers (SAE).

Britain: The British Standards Institution (BSI).

Germany: The Verband der Elektrotechnik, Elektronik und Informationstechnik (VDE) or Association

for Electrical, Electronic and Information Technologies.

[edit]Laws

Compliance with national or international standards is usually required by laws passed by individual

nations. Different nations can require compliance with different standards.

By European law, manufacturers of electronic devices are advised to run EMC tests in order to comply with

compulsory CE-labeling. Undisturbed usage of electric devices for all customers should be ensured and the

electromagnetic field strength should be kept on a minimum level. EU directive 2004/108/EC (previously

89/336/EEC) on EMC announces the rules for the distribution of electric devices within the European

Union. A good overview of EME limits and EMI demands is given in List of EMC directives.

[edit]EMC design

A TV tuner card showing many small bypass capacitors, and 2 CCA shields -- a metal box shielding the coax inputs and

another metal box shielding the S-Videoconnector

Main article: EMC problem (excessive field strength)

Electromagnetic noise is produced in the source due to rapid current and voltage changes, and spread via

the coupling mechanisms described earlier.

Since breaking a coupling path is equally effective at either the start or the end of the path, many aspects

of good EMC design practice apply equally to potential emitters and to potential victims. Further, a circuit

which easily couples energy to the outside world will equally easily couple energy in and will be

susceptible. A single design improvement often reduces both emissions and susceptibility.

[edit]Grounding and shielding

Grounding and shielding aim to reduce emissions or divert EMI away from the victim by providing an

alternative, low-impedance path. Techniques include:

Shielded  housings.

In order to access the components, a housing is typically made in sections (such as a box and lid);

an RF gasket is often used at the section joints to reduce the amount of interference that leaks

through the joint. RF gaskets come in various types. One type is based on a waterproof flexible

elastomeric base with chopped metal fibers dispersed into the interior or long metal fibers covering

the surface or both. ("oriented wire gasket", "woven mesh gasket", etc.) Another type is RF

fingerstock comprises springy metal "fingers".

Shielded cables, where the conducting wires are surrouned by an outer conductive layer that is

grounded at one or both ends.

Grounding or earthing schemes such as star earthing for audio equipment or ground planes for

RF.

[edit]Other general measures

Decoupling  or filtering at critical points such as cable entries and high-speed switches, using RF

chokes and/or RC elements.

Transmission line techniques for cables and wiring, such as balanced differential signal and

return paths, and impedance matching.

Avoidance of Antenna Structures, such as loops of circulating current, resonant mechanical

structures, unbalanced cable impedances or poorly grounded shielding.

[edit]Emissions suppression

Spread spectrum method reduces EMC peaks. Frequency spectrum of the heating up period of a switching

power supply which uses the spread spectrum method incl. waterfall diagram over a few minutes

Additional measures to reduce emissions include:

Avoid unnecessary switching operations. Necessary switching should be done as slowly as

technically possible.

Noisy circuits (with a lot of switching activity) should be physically separated from the rest of the

design.

High peaks can be avoided by using the spread spectrum method.

Harmonic  Wave Filters.

Design for operation at lower signal levels, reducing the energy available for emission.

[edit]Susceptibility hardening

Additional measures to reduce susceptibility include:

Fuses, trip switches and circuit breakers.

Transient absorbers.

Design for operation at higher signal levels, reducing the relative noise level in comparison.

[edit]EMC testing

Testing is required to confirm that a particular device meets the required standards. It divides broadly

into emissions testing and susceptibility testing.

RF testing of a physical prototype is most often carried out in a radio-frequency anechoic chamber.

Open-air test sites, or OATS, are the reference sites in most standards. They are especially useful for

emissions testing of large equipment systems.

Sometimes computational electromagnetics simulations are used to test virtual models.

Like all compliance testing, it is important that the test equipment, including the test chamber or site

and any software used, be properly calibrated and maintained.

Typically, a given run of tests for a particular piece of equipment will require an EMC test plan and

follow-up Test report. The full test program may require the production of several such documents.

[edit]Susceptibility testing

Radiated field susceptibility testing typically involves a high-powered source of RF or EM pulse energy

and a radiating antenna to direct the energy at the potential victim or device under test (DUT).

Conducted voltage and current susceptibility testing typically involves a high-powered signal or pulse

generator, and a current clamp or other type of transformer to inject the test signal.

Transient immunity is used to test the immunity of the DUT against powerline disturbances including

surges, lightning strikes and switching noise.[2] In motor vehicles, similar tests are performed on

battery[3] and signal lines.[4]

Electrostatic discharge testing is typically performed with a piezo spark generator called an "ESD

pistol". Higher energy pulses, such as lightning or nuclear EMP simulations, can require a largecurrent

clamp or a large antenna which completely surrounds the DUT. Some antennas are so large that they

are located outdoors, and care must be taken not to cause an EMP hazard to the surrounding

environment.

[edit]Emissions testing

Emissions are typically measured for radiated field strength and where appropriate for conducted

emissions along cables and wiring. Inductive (magnetic) and capacitive (electric) field strengths are

near-field effects, and are only important if the device under test (DUT) is designed for location close to

other electrical equipment.

Typically a spectrum analyzer is used to measure the emission levels of the DUT across a wide band

of frequencies (frequency domain). Specialized spectrum analyzers for EMC testing are available,

called EMI Test Receivers or EMI Analyzers. These incorporate bandwidths and detectors as specified

by international EMC standards. EMI Receivers along with specified transducers can often be used for

both conducted and radiated emissions. Pre-selector filters may also be used to reduce the effect of

strong out-of-band signals on the front-end of the receiver.

For conducted emissions, typical transducers include the LISN (Line Impedance Stabilisation Network)

or AMN (Artificial Mains Network) and the RF current clamp.

For radiated emission measurement, antennas are used as transducers. Typical antennas specified

include dipole, biconical, log-periodic, double ridged guide and conical log-spiral designs. Radiated

emissions must be measured in all directions around the DUT.

Some pulse emissions are more usefully characterized using an oscilloscope to capture the pulse

waveform in the time domain.

[edit]History

The earliest EMC issue was lightning strike (Lightning Electromagnetic Pulse, or LEMP) on

buildings. Lightning rods or lightning conductors began to appear in the mid-18th century. With the

advent of widespread electricity generation and power supply lines from the late 19th century on,

problems also arose with equipment short-circuit failure affecting the power supply, and with local fire

and shock hazard when the power line was struck by lightning. Power stations were provided with

output circuit breakers. Buildings and appliances would soon be provided with input fuses, and later in

the 20th century miniature circuit breakers (MCB) would come into use.

As radio communications developed in the first half of the 20th century, interference

between broadcast radio signals began to occur and an international regulatory framework was set up

to ensure interference-free communications.

As switching devices became commonplace, typically in petrol powered cars and motorcycles but also

in domestic appliances such as thermostats and refrigerators, transient interference with domestic

radio and (after World War II) TV reception became problematic, and in due course laws were passed

requiring the suppression of such interference sources.

ESD problems first arose with accidental electric spark discharges in hazardous environments such as

coal mines and when refuelling aircraft or motor cars. Safe working practices had to be developed.

After World War II the military became increasingly concerned with the effects of nuclear

electromagnetic pulse (NEMP), lightning strike, and even high-powered radar beams, on vehicle and

mobile equipment of all kinds, and especially aircraft electrical systems.

When high RF emission levels from other sources became a potential problem (such as with the

advent of microwave ovens), certain frequency bands were designated for Industrial, Scientific and

Medical (ISM) use, allowing unlimited emissions. A variety of issues such as sideband and harmonic

emissions, broadband sources, and the increasing popularity of electrical switching devices and their

victims, resulted in a steady development of standards and laws.

From the 1970s, the popularity of modern digital circuitry rapidly grew. As the technology developed,

with faster switching speeds (increasing emissions) and lower circuit voltages (increasing

susceptibility), EMC increasingly became a source of concern. Many more nations became aware of

EMC as a growing problem and issued directives to the manufacturers of digital electronic equipment,

which set out the essential manufacturer requirements before their equipment could be marketed or

sold. Organizations in individual nations, across Europe and worldwide, were set up to maintain these

directives and associated standards. This regulatory environment led to a sharp growth in the EMC

industry supplying specialist devices and equipment, analysis and design software, and testing and

certification services.

Low-voltage digital circuits, especially CMOS transistors, became more susceptible to ESD damage as

they were miniaturised, and a new ESD regulatory regime had to be developed.

From the 1980s, the ever-increasing use of mobile communications and broadcast media channels

has put huge pressure on the available airspace. Regulatory authorities are squeezing band

allocations closer and closer together, relying on increasingly sophisticated EMC control methods,

especially in the digital communications arena, to keep cross-channel interference to acceptable

levels. Digital systems are inherently less susceptible than the old analog systems, and also offer far

easier ways (such as software) to implement highly sophisticated protection measures.

Most recently, even the ISM bands are being used for low-power mobile digital communications. This

approach relies on the intermittent nature of ISM interference and use of sophisticated error-

correction methods to ensure lossless reception during the quiet gaps between bursts of interference.

[edit]EMC test equipment manufacturers (alphabetic)

Aaronia

Aeroflex

Agilent  (formerly the test and measurement division of Hewlett-Packard)

Anritsu

MILMEGA

National Instruments

Rohde & Schwarz

Tektronix

Teseq  (formerly Schaffner)

Würth

IEEE Electromagnetic Compatibility SocietyFrom Wikipedia, the free encyclopedia

IEEE Electromagnetic Compatibility Society

Formation 1957

Official languages English

Website emcs.org

The IEEE Electromagnetic Compatibility Society (EMCS) is an organizational unit and professional

society of academic professors and applied engineers with a common interest, affiliated with the IEEE. The

50-year-old Society has members and chapters in nearly every country throughout the world. As an active

entity within the IEEE, benefits are provided to members as detailed below.

IEEE Logo

EMC Society Logo

Contents

  [hide]

1   Field of Interest

2   History

3   Today’s IEEE EMC Society

4   Technical Committees

5   External links

6   References

[edit]Field of Interest

The electromagnetic compatibility field of interest is on engineering related to

the electromagnetic environmental effects of systems to be compatible with themselves and their intended

operating environment.

These areas include: standards, measurement techniques and test procedures, instrumentation, equipment

and systems characteristics, interference control techniques and components, education, computational

analysis, and spectrum management, along with scientific, technical, industrial, professional or other

activities that contribute to this field.

[edit]History

Fifty years ago, a small group of electrical engineers and associated technical people realized it would be a

prudent step to organize a group of individuals dedicated to Radio Frequency Interference (RFI). Two

different sets of individuals, one on the West Coast of the United States and the other on the East Coast,

began to discuss organizational considerations, generated signed petitions, and met with officials of

the Institute of Radio Engineers (IRE) in [New York City].

These early efforts culminated in a formal petition to the Institute of Radio Engineers (IRE) on 3 July 1957,

requesting the formation of an Institute of Radio Engineers Professional Group onRadio Frequency

Interference (RFI). This petition, which included a scope of technical interest, was approved by the IRE on

10 October 1957.

The first meeting of the Administrative Committee of the newly formed group was held on 20 November

1957 in Asbury Park, New Jersey. Officers were elected and the group was operations.

The Professional Groups on Radio Frequency Interference became the Professional Group on RFI in

the Institute of Electrical and Electronic Engineers (IEEE) in 1963 when the IRE and theAmerican Institute

of Electrical Engineers merged. Within five years, the Professional Group became the EMC Society of

the IEEE, a name that has remained constant for 40 years.

In 2007, the IEEE EMC Society celebrated its 50th anniversary at their yearly conference

in Honolulu, Hawaii. To help celebrate, the Society’s celebration pin was flown in space shuttle

mission,STS-118 (August 8–21, 2007). This pin is mounted in a frame with a photograph of the astronauts,

officers of the EMC Society, and is on display at the IEEE Headquarter office in Piscataway,New Jersey,

History Center.[1]

[edit]Today’s IEEE EMC Society

The IEEE EMC Society has evolved into an international, professional society within the IEEE. The Society

has 65 chapters worldwide and membership of approximately 4,000 (as of June 2008). The governing body

is identified as the Board of Directors consisting of a President, five Vice Presidents, and Directors-at-Large

elected by the membership.

Benefits to both members and non-members interested in the IEEE EMC Society includes:

A Transactions (or Journal) on Electromagnetic Compatibility

A quarterly newsletter

An annual symposium or conference

Chapter development program

Eleven technical committees

Professional committees related to education, standards and third-party organizations

A distinguished lecturer program

Details on the above programs are found on the society’s web site: www.emcs.org.

The EMC Society is organized into different areas of interest, each with a Vice President who oversees

operational aspects under his/her leadership.

Member Services

Technical Services

Communication Services

Conferences

Standards

[edit]Technical Committees

There are eleven Technical Committees of the IEEE EMC Society along with several specialized

committees. These committees provide technical guidance to the Board of Directors and the general

membership. Each of the technical committees provides expertise in a particular technical area while other

committees have a focus on Society operations worldwide.

Technical Activities Committee

TC-1 EMC Management

TC-2 EMC Measurements

TC-3 Electromagnetic Environment

TC-4 Electromagnetic Interference Control

TC-5 High Power Electromagnetics

TC-6 Spectrum Management

TC-7 Nonsinusoidal Fields

TC-8 Electromagnetic Product Safety

TC-9 Computational Electromagnetic

TC-10 Signal Integrity

TC-11 Nanotechnology

Representative Advisory Committee

Education and Student Activities Committee

Standards Committee

[edit]External links

IEEE

IEEE EMC Society

EMC Society Orange County, California chapter

IEEE Germany Section EMC Society Chapter

IEEE Hong Kong Section EMC Society Chapter

[edit]References

1. ̂  IEEE Global History Network (2011). "IEEE Electromagnetic Compatibility Society History". IEEE

History Center. Retrieved 27 June 2011.

Charging stationFrom Wikipedia, the free encyclopedia

This article covers electrical recharging. For pneumatic recharging, see compressed air vehicle.

Nissan Leaf charging from an Andromeda Power ORCA mobile charger inAnaheim, California.

Nissan Leaf recharging from a NRG Energy eVgo station in Houston, Texas

Public charging stations in San Francisco2009

Brammo Empulse electric motorcycle at aAeroVironment charging station

An electric vehicle charging station, also called EV charging station, electric recharging

point, charging point and EVSE (Electric Vehicle Supply Equipment), is an element in an infrastructure

that supplies electric energy for the recharging of plug-in electric vehicles, including all-electric

cars, neighborhood electric vehicles and plug-in hybrids. As of October 2012, the United States had 13,967

public charging units, of which 3,472 were located in California.[1] As of November 2012, about 15,000

charging stations had been installed in Europe,[2] of which, Norway, the world's leader in electric car

ownership per capita, had 3,708 free public charging points through November 2012.[3] As of December

2011, Japan had 800 public quick-charge stations,[4] and China only 168 public charging stations.[5]

As plug-in hybrid electric vehicles and battery electric vehicle ownership is expanding, there is a growing

need for widely distributed publicly accessible charging stations, some of which support faster charging at

higher voltages and currents than are available from domestic supplies. Many charging stations are on-

street facilities provided by electric utility companies, mobile charging stations have been recently

introduced. Some of these special charging stations provide one or a range of heavy duty or special

connectors and/or charging without a physical connection using parking places equipped with inductive

charging mats.

Contents

  [hide]

1   Overview

o 1.1   Safety

o 1.2   Standards

2   Mode 1: Household socket and extension cord

o 2.1   No dedicated circuit

o 2.2   Temperature derating and intensive use

o 2.3   Obsoleteness and non-compliance

3   Mode 2: Domestic socket and cable with a protection device

4   Mode 3: Specific socket on a dedicated circuit

5   Mode 4: Direct current (DC) connection for fast recharging

o 5.1   Evolution

6   Charging time

7   Infrastructure

8   Smart grid communication

9   Deployment of public charging stations

o 9.1   Locations

o 9.2   Vehicle and charging station projects and joint ventures

o 9.3   List of EV charging station designers

9.3.1   Slow charge

9.3.2   Fast and slow charge

o 9.4   EV charging station signs

o 9.5   Block heater power supplies

10   Battery swapping

o 10.1   Incidents

11   Renewable electricity and RE charging stations

o 11.1   SPARC station

o 11.2   E-Move charging station

o 11.3   Wind-powered charging station

12   See also

13   Notes

14   External links

[edit]Overview

Public-domain European charge station sign

U.S. traffic sign used for EV charging station

[edit]Safety

Although most rechargeable electric vehicles and equipment can be recharged from a domestic wall

socket, a charging station is usually accessible to multiple electric vehicle (EV) owners and has additional

current or connection sensing mechanisms to disconnect the power when the EV is not actually charging.

This is in case an EV should be carelessly driven away before being unplugged, and so violently rip away

the charging cable insulation and expose the electric conductors, which (except for the sensor mechanism)

could be dangerous.

There are two main types of safety sensor:

additional physical 'sensor wires' which provide a feedback signal such as specified by the

undermentioned SAE J1772 and IEC 62196 schemes that require special (multi-pin) power plug

fittings,

Current sensors which monitor the power consumed, and only maintain the connection if the demand

is within a "window" (for example between 1 ampere and 15 amperes).

Sensor wires react more quickly, have less parts to fail and are possibly less expensive to design and

implement. Current sensors however can use standard connectors and can readily provide an option for

suppliers to monitor or charge for the electricity actually consumed.

[edit]Standards

In SAE terminology, 240 volt AC charging is known as level 2 charging, and 500 volt DC high-current

charging is known as DC Fast Charge. Owners can install a level 2 charging station at home, while

businesses and local government provide level 2 and DC Fast Charge public charging stations that supply

electricity for a fee or free.

The International Electrotechnical Commission (IEC) modes are similar:

Mode 1 - slow charging from a regular electrical socket (1- or 3-phase)

Mode 2 - slow charging from a regular socket but which equipped with some EV specific protection

arrangement (e.g., the Park & Charge or the PARVE systems)

Mode 3 - slow or fast charging using a specific EV multi-pin socket with control and protection

functions (e.g., SAE J1772 and IEC 62196)

Mode 4 - fast charging using some special charger technology such as CHAdeMO.

There are also three connection cases with which mode is sometimes confused

Case A is any charger connected to the mains (the mains supply cable is usually attached to the

charger) usually associated with modes 1 or 2

Case B is an on-board vehicle charger with a mains supply cable which can be detached from both the

supply and the vehicle - usually mode 3

Case C is a dedicated charging station with DC supply to the vehicle. The mains supply cable may be

permanently attached to the charge-station such as in mode 4.

And finally there are four plug types

Type 1 - single phase vehicle coupler - reflecting the SAE J1772/2009 automotive plug specifications

Type 2 - single and three phase vehicle coupler - reflecting the VDE-AR-E 2623-2-2 plug specifications

Type 3 - single and three phase vehicle coupler equipped with safety shutters - reflecting the EV Plug

Alliance proposal

Type 4 - fast charge coupler - for special systems such as CHAdeMO

[edit]Mode 1: Household socket and extension cord

This section does not cite any references or sources. Please help improve this section by adding citations to reliable sources. Unsourced material may be challenged and removed. (December 2012)

The vehicle is connected to the power grid through standard socket-outlets present in residences, which

depending on the country are usually rated at around 10 A. To use mode 1, the electrical installation must

comply with the safety regulations and must have an earthing system, a circuit breaker to protect against

overload and an earth leakage protection. The sockets have blanking devices to prevent accidental

contacts. This solution is the simplest and the most direct to implement. It offers the driver the option of

charging his /her vehicle almost everywhere, which guarantees the peace of mind for the first-time buyers

of electric vehicles. However, this solution may pose risks if used incorrectly and has several serious

limitations which has led to the definition of other more efficient charging modes.

Mode 1 : Fixed, non-dedicated socket.

The first limitation is the available power, to avoid risks of

heating of the socket and cables following intensive use for several hours at or near the maximum

power (which varies from 8 to 16 A depending on the country)

fire or electric injury risks if the electrical installation is obsolete or if certain protective devices are

absent.

The second limitation is related to the installation's power management

as the charging socket shares a feeder from the switchboard with other sockets (no dedicated circuit) if

the sum of consumptions exceeds the protection limit (in general 16 A), the circuit-breaker will trip,

stopping the charging.

All these factors impose a limit on the power in mode 1, for safety and service quality reasons. This limit is

currently being defined, and the value of 10 A appears to be the best compromise. At this power, it will take

nearly 10 hours to fully charge a vehicle.

[edit]No dedicated circuit

For instance, in France, the local standard NF-C-15100 standard on installation allows the connection of

several household socket-outlets into the same protective element of the dwelling's electrical switchboard:

Up to 5 socket-outlets with a cable with a cross-section 1.5 mm2.

Protection by a 16 A circuit breaker.

Up to 8 socket-outlets with a cable with a cross-section 2.5 mm2.

Protection by a 20 A circuit breaker.

It is therefore highly probable that the household socket used for charging an electric vehicle is on the

same circuit as another electrical appliance, which may also be in operation during the charging.

In this case, the OCP, Overcurrent Protective Device, will open for safety reasons, as the cumulated

currents of the electric vehicle and the household appliance will be higher than its setting threshold.

Installation of a dedicated circuit for electric vehicle charging can prevent this type of unwanted tripping.

Ensuring that any load or appliances on the shared EV charging circuit are turned off while charging, can

prevent the OCP from tripping as well. This can be difficult to ensure, so a dedicated circuit is the most

reliable solution.

[edit]Temperature derating and intensive use

Fully electric vehicles have charging powers varying from 3 to 24 kW. These powers correspond to

charging currents from 16 A single-phase up to 32 A three-phase. Moreover, charging the vehicle may take

up to 8 hours, and this has to be done regularly, even on a daily basis.

The NF-C-15100 standard imposes cable cross-sections of 1.5 mm2 or 2.5 mm2. Their maximum

permissible power is 3.7 kW for a 1.5 mm2 cable and up to 5.7 kW for a 2.5 mm2 cable.

Household sockets are designed to be used at full load only for a limited period (typically 1 hour at

maximum power, which is the case when we use household appliances). When charging an electric

vehicle, the charging time exceeds this limit and can last up to 6 or 8 hours. Household sockets must

therefore be classified as derating systems for this use case: their permissible current must be lower than

16 A or 32 A in order to limit abnormal temperature increases in components and to prevent fire hazards.

[edit]Obsoleteness and non-compliance

In France, electrical installation professionals believe that there are about 7 million hazardous electrical

installations (obsolete, non-compliant, etc.), accounting for a little less than half of the old residential

building stock.

Mode 2 : Non-dedicated socket with cable-incorporated protection device.

For instance in France, from 1972 onwards, new electrical installations are subject to an inspection and an

attestation of compliance. This measure instituted by public authorities was extended in 2001 to the

electrical installations of fully renovated dwellings.

However, the electrical installations of the 16 million dwellings built before 1972 are not covered by any

regulatory control measure.

There are also misgivings about the condition of electrical installations in the dwellings built after 1972:

according to electrical safety experts, an installation in which no change has been made for the last 30

years can be considered as obsolete. They further believe that, after thirty years, even in normal usage

conditions, an electrical installation may most likely pose hazards due to wear and tear if no maintenance

operation has been carried out since it was set up.

Connecting an electric vehicle without any precaution to this type of installation can therefore be dangerous

for people and property when appropriate protective devices are absent.

Mode 3 : Fixed, dedicated circuit-socket.

[edit]Mode 2: Domestic socket and cable with a protection device

The vehicle is connected to the main power grid via household socket-outlets. Charging is done via a

single-phase or three-phase network and installation of an earthing cable. A protection device is built into

the cable. This solution is particularly expensive due to the specificity of the cable.

Mode 4 : CC Connexion.

[edit]Mode 3: Specific socket on a dedicated circuit

The vehicle is connected directly to the electrical network via specific socket and plug and a dedicated

circuit. A control and protection function is also installed permanently in the installation. This is the only

charging mode that meets the applicable standards regulating electrical installations. It also allows load-

shedding so that electrical household appliances can be operated during vehicle charging or on the

contrary optimise the electric vehicle charging time.

[edit]Mode 4: Direct current (DC) connection for fast recharging

The electric vehicle is connected to the main power grid through an external charger. Control and

protection functions and the vehicle charging cable are installed permanently in the installation.

[edit]Evolution

The coordinated development of charging stations in a region by a company or local government is more

fully discussed in the electric vehicle network article. Currently charging stations are being installed by

public authorities, commercial enterprises and some major employers in order to stimulate the market for

vehicle that use alternative fuels to gasoline & diesel fuels. For this reason most charge stations are

currently either provided gratis or accessible to members of certain groups without significant charge (e.g.

activated by a free "membership card" or by a digital "day code").

[edit]Charging time

The battery capacity of a fully charged electric vehicle is about 20 kWh, providing it with an electrical

autonomy of about 100 kilometres; chargeable hybrid vehicles have capacity of roughly 3 to 5 kWh, for an

electrical autonomy of 20 to 40 kilometres (the gasoline engine ensures the autonomy of a conventional

vehicle).

As this autonomy is still limited, the vehicle has to be charged every 2 or 3 days on average. In practice,

drivers charge their vehicles every 1 or 2 days on average.

For normal charging (3 kW), car manufacturers have built a battery charger into the car. A charging cable is

used to connect it to the electrical network to supply 230 volt AC current. For quicker charging (22 kW,

even 43 kW and more), manufacturers have chosen two solutions: - use the vehicle's built-in charger,

designed to charge from 3 to 43 kW at 230 V single-phase or 400 V three-phase. - use an external charger,

which converts AC current into DC current and charges the vehicle at 50 kW.

Charging time Power supply VoltageMax

current

6–8 hours Single phase - 3,3 kW 230 VAC 16 A

2–3 hours Three phase - 10 kW 400 VAC 16 A

3–4 hours Single phase - 7 kW 230 VAC 32 A

1–2 hours Three phase - 24 kW 400 VAC 32 A

20–30 minutes Three phase - 43 kW 400 VAC 63 A

20–30 minutes Direct current - 50 kW 400 - 500 VDC 100 - 125 A

The user finds charging an electric vehicle as simple as connecting a normal electrical appliance; however

to ensure that this operation takes place in complete safety, the charging system must perform several

safety functions and dialogue with the vehicle during connection and charging.

[edit]Infrastructure

Project Better Place charging stations inRamat Hasharon, Israel, north of Tel Aviv.

Public charging station in a parking lotnear Los Angeles International Airport. Shown are two old-style (6kW level2)

EVSE units (left: inductive Magne-charge gen2 SPI, right: conductive EVII ICS-200 AVCON.

REVAi/G-Wiz i charging from an on-street station in London.

Charging stations for electric vehicles may not need much new infrastructure in developed countries, less

than delivering a new alternative fuel over a new network.[6] The stations can leverage the existing

ubiquitous electrical grid and home recharging is an option. For example, polls have shown that more than

half of homeowners in the USA have access to a plug to charge their cars.[citation needed] Also most driving is

local over short distances which reduces the need for charging mid-trip. In the USA, for example, 78% of

commutes are less than 40 miles (64 km) round-trip.[7] Nevertheless, longer drives between cities and

towns require a network of public charging stations or another method to extend the range of electric

vehicles beyond the normal daily commute. One challenge in such infrastructure is the level of demand: an

isolated station along a busy highway may see hundreds of customers per hour if every passing electric

vehicle has to stop there to complete the trip. In the first half of the 20th century, internal combustion

vehicles faced a similar infrastructure problem.

[edit]Smart grid communication

Recharging a large battery pack presents a high load on the electrical grid, but this can be scheduled for

periods of reduced load or reduced electricity costs. In order to schedule the recharging, either the charging

station or the vehicle can communicate with the smart grid. Some plug-in vehicles allow the vehicle

operator to control recharging through a web interface or smartphone app.[citation needed] Furthermore, in

a Vehicle-to-grid scenario the vehicle battery can supply energy to the grid at periods of peak demand. This

requires additional communication between the grid, charging station, and vehicle electronics. SAE

International is developing a range of standards for energy transfer to and from the grid including SAE

J2847/1 "Communication between Plug-in Vehicles and the Utility Grid".[8]

[edit]Deployment of public charging stations

[edit]Locations

Charging stations can be found and will be needed where there is on-street parking, at taxi stands,

in parking lots (at places of employment, hotels, airports, shopping centers, convenience shops, fast food

restaurants, coffeehouses etc.), phone booths, as well as in driveways and garages at home. Existing filling

stations may also become or may incorporate charging stations. They can be added onto other public

infrastructure that has an electrical supply, such as phone booths[9] and smart parking meters.

Anxiety regarding range and finding charging stations can be a major concern for EV drivers; this can be

helped with online directories such as EV-Networks[10] or some charging station providers like POD Point in

the UK publish live availability[11] of their charging locations for EV drivers.

In the UK most charging points have highly visible indicator lights[12] on the charging point to show whether

it is available, charging or out of service.

[edit]Vehicle and charging station projects and joint ventures

Wireless charging station

Detail of the wireless inductive charging device

Main article: Electric vehicle network

Electric car manufacturers, charging infrastructure providers, and regional governments have entered into

many agreements and ventures to promote and provide electric vehicle networks of public charging

stations.

The EV Plug Alliance [13]  is an association of 21 European manufacturers which proposes a safe connecting

solution. The project is to impose an IECnorm and to adopt a European standard for the connection

solution with sockets and plugs for electric vehicle charging infrastructure.

The EV Plug Alliance has the highest safety level thanks to the adoption of protective shutters to prevent

any accidental contact with live parts and the expertise of its members: Schneider Electric, Legrand,

Scame, Nexans, etc.

[edit]List of EV charging station designers

The principal suppliers and manufacturers of charging stations offer a range of options from simple

charging posts for roadside use, charging cabinets for covered parking places to fully automated charging

stations integrated with power distribution equipment[14]

[edit]Slow charge

Design concentration in systems that may take up to 6 hours and in automated chargers which are likely to

provide a full (100%) charge and conserve battery life.

PARVE Charging System  A Spanish design

SemaConnect  A US maker of Charge Pro Level 1 outlets

[edit]Fast and slow charge

Design concentration on DC Fast Charge (less than 30 minutes). These systems may offer a restricted

charge (stops at 80% SOC), or changes charging rate to a lower level after the 80% SOC is reached.

AeroVironment

Better Place

Coulomb Technologies

EvStations.net

ECOtality

Elektromotive

IAV  A German design for an In-Road Electric Vehicle Charger

OpConnect Electric Vehicle Charging System

Schneider Electric

[edit]EV charging station signs

In the United States, the standard charging station sign is defined in the Federal Highway

Administration's Manual on Uniform Traffic Control Devices (MUTCD) 2009 edition .

See two examples of "D9-11b Electric Vehicle Charging" and "D9-11bP Electric Vehicle Charging"

at "Figure 2I-1. General Service Signs and Plaques", page 301, Sect. 2I.02

There is an open source, public domain European charge station sign proposed.[15]

[edit]Block heater power supplies

In colder areas such as Finland, some northern US states and Canada there already exists some

infrastructure for public power outlets provided primarily for use by block heaters and set with circuit

breakers that prevent large current draws for other uses. These can sometimes be used to recharge

electric vehicles, albeit slowly. In public lots, some such outlets are only turned on when the

temperature falls below -20°C, further limiting their use.[16]

[edit]Battery swapping

A charging station is different from a battery switch station, which is a place to swap a discharged

battery or battery pack for a fully charged one, saving the delay of waiting for the vehicle's battery to

charge. Battery swapping is common in warehouses using electric forklift trucks.[17] The

companies Better Place, Tesla Motors, Mitsubishi Heavy Industries [18]  and others are currently working

in integrating battery switch technology in their electric vehicles to extend their driving range. Better

Place is using the same technology to swap batteries that F-16 jet fighter aircraft use to load their

bombs.[19]

In a battery switch station, the driver does not need to get out of the car while the battery is swapped.

[20] Better Place's automated battery-switching station (also called Quickdrop Stations) can complete a

battery swap in less than one minute,[21] which is faster than refueling a conventional petrol car.

SwapPack, a Texas entity, is developing as of April 2010 a swap arrangement, similar to the swapping

out of butane gas tanks at convenience stores, a similar swap at car dealerships and large wholesale

big box retailers. These locations will allow drivers the security of making a quick change of battery

packs to have a power pack that is totally recharged. As of November 2010 the batteries of existing

hybrid/electric cars, i.e. Prius, have not yet expired after a 100,000-mile (160,000 km) duration.

Battery swap depends on at least one electric car designed for "easy swap" of batteries. However,

electric vehicle manufacturers that are working on battery switch technology have not standardized on

battery access, attachment, dimension, location, or type. Better Place announced the Renault Fluence

Z.E. would be the first electric car with a switchable battery available on the Better Place network,

[22] also Tesla Motors are integrating one minute battery switch technology[23] in their Model S sedan

with the possibility to rent 300-mile (480 km) batteries for longer trips.[24]

Summary of benefits of battery swapping:

Fast battery swapping of around 59.1 seconds.[21]

Unlimited driving range where there are battery switch stations available.[25]

The driver does not have to get out of the car while the battery is swapped.[26]

The driver does not own the battery in the car, transferring costs over the battery, battery life,

maintenance, capital cost, quality, technology, and warranty to the battery switch station

company.[27]

Contract with battery switch company could subsidize the electric vehicle at a price lower than

equivalent petrol cars.[28]

The spare batteries at swap stations could participate in vehicle to grid storage.[citation needed]

[edit]Incidents

In 2011 a Zotye Langyue EV taxicab in Hangzhou, China caught fire and was destroyed, although the

driver and passenger were able to escape unharmed. Later investigation by the city's Quality

Supervision and Inspection Administration revealed that the fire had been caused by an issue with

taxi's defective swappable battery pack. Although the batteries themselves were not designed for

automotive use, the battery pack had been poorly taken care of which caused damage to the insulation

between the battery cells and the aluminum casing, creating numerous short circuits. It was one of the

stronger short circuits which ignited the car. The remaining 29 taxicabs belonging to the city (14

produced by Zotye International and 15 produced by Haima) were withdrawn from service that day and

modified before going back into service.[29]

[edit]Renewable electricity and RE charging stations

A modified Toyota Prius and Honda Insight at a charging station in Rio De Janeiro. This station is run

by Petrobras and uses solar energy.

See also: Solar-charged vehicle

Charging stations are usually connected to the electrical grid, which often means that their electricity

originates from fossil-fuel power stations or nuclear power plants. Solar power is also suitable

for electric vehicles. SolarCity is marketing its solar energy systems along with electric car charging

installations. The company has announced a partnership with Rabobank to make electric car charging

available for free to owners of Tesla Motors' vehicles traveling on Highway 101 between San

Francisco and Los Angeles. Other cars that can make use of same charging technology are welcome.

[30]

[edit]SPARC station

The SPARC (Solar Powered Automotive ReCharging Station uses a single custom

fabricated monocrystalline solar panel capable of producing 2.7 kW of peak power to charge pure

electric or plug-in hybrid to 80% capacity without drawing electricity from the local grid. Plans for the

SPARC include a non-grid tied system as well as redundancy for tying to the grid through a renewable

power plan. This supports their claim for net-zero driving of electric vehicles.

[edit]E-Move charging station

The E-Move Charging Station is equipped with eight monocrystalline solar panels, which can supply

1.76KWp of solar power. With further refinements, the designers are hoping to generate about

2000KWh of electricity from the panels over the year.[31]

[edit]Wind-powered charging station

In 2012, Urban Green Energy introduced the world's first wind-powered electric vehicle charging

station, the Sanya SkyPump. The design features a 4 kW vertical-axis wind turbine paired with a GE

WattStation. [32]

[edit]See also

Automated charging machine

Battery charger

Battery leasing

Direct coupling

Dump charging

Electric vehicle battery

Electric vehicle network

EV Project

Filling station

IAV

In-road electric vehicle charger

Lamppost

Magne Charge

Park & Charge

Plug-in vehicle

Plug-in hybrid vehicle

Plugless Power

RFID

SAE J1772  and CHAdeMO charging standards

Solar-charged vehicle

Transport electrification

V2G , V2Green and V2H

[edit]Notes

1. ̂  U.S. Department of Energy (2012-10-31). "Alternative Fueling Station Counts by State".

Alternative Fuels Data Center (AFDC). Retrieved 2012-11-16. The AFDC counts electric charging

units, or EVSE, as one for each outlet available.

2. ̂  Renault Press Release (2012-12-17). "Renault delivers first ZOE EV". Green Car Congress.

Retrieved 2012-12-17.

3. ̂  "Ladepunkter i Norge [Charging points in Norway]" (in Norwegian). Grønn bil. December 2012.

Retrieved 2012-12-17.

4. ̂  Brad Berman (2011-11-06). "Electric Car Quick Charging in Japan: It’s Nissan Versus Everybody

Else". PluginCars.com. Retrieved 2012-05-22.

5. ̂  "2012 Chinese Auto Industry Development Report". Green Car Congress. 2012-07-09. Retrieved

2012-07-10.

6. ̂  "Plug-In 2008: Company News: GM/V2Green/Coulomb/Google/HEVT/PlugInSupply".CalCars.

2008-07-28. Retrieved 2010-05-30.

7. ̂  Source: US Department of Transportation, Bureau of Transportation Statistics, Omnibus

Household Survey. Data from the February, April, June, and August 2003 surveys have been

combined. Data cover activities for the month prior to the survey. (October 2003). "From Home to

Work, the Average Commute is 26.4 Minutes". OmniStats 3 (4). Retrieved 2009-10-15.

8. ̂  "SAE Ground Vehicle Standards Status of work – PHEV +". SAE International. 2010-01. pp. 1–7.

Retrieved 2010-09-03.

9. ̂  "ENDESA AND TELEFÓNICA LAUNCH FIRST ELECTRIC VEHICLE TELEPHONE BOOTH

RECHARGING STATION." (Press release). Endesa. 2010-05-10. Retrieved 2010-05-21.

10. ̂  http://www.ev-network.org.uk/Default.aspx?pageId=524100

11. ̂  http://www.pod-point.com/live-availabilty/

12. ̂  http://www.pod-point.com/using-pod-point/

13. ̂  http://www.evplugalliance.org/

14. ̂  "Electric vehicles - About electric vehicles - Charging - suppliers". Public authority

announcement. The Mayor of London for the London Assembly and the Greater London Authority,

UK. First published 2009. Retrieved 2011-11-24.

15. ̂  http://evinfra.org

16. ̂  Park and Ride Locations, Calgary Transit, 16 April 2009, retrieved 2009-04-25, "The plug-ins

located in the Park and Ride lots automatically turn on when the outside temperature falls below -

20 degrees and turn off and on in increments to save electricity usage."

17. ̂  "Industrial electrical vehicle stalwarts head out on the road".

18. ̂  "Mitsubishi working on battery swapping for transit buses, Better Place not involved".

19. ̂  "Charging Ahead With a New Electric Car".

20. ̂  "Better Place. Battery switch stations".

21. ^ a b "Better Place expands Tokyo battery swap trials; taxis have changed packs 2,122 times

already".

22. ̂  "Better Place. The Renault Fluence ZE". Better Place. 2010-10-22. Retrieved 2010-10-22.

23. ̂  "Tesla Model S specs".

24. ̂  "Tesla Model S customers will be able to swap batteries at Tesla dealerships with the possibility

to rent 300 mile batteries for longer trips.".

25. ̂  "Better Place, California Battery Switch Station Deployment".

26. ̂  "Better Place, battery switch station description".

27. ̂  "Lithium Ion Israel".

28. ̂  "Better Place's Renault Fluence EV to sell for under $20,000".

29. ̂  "Battery Pack Defects Blamed for Zotye EV Fire". ChinaAutoWeb. Retrieved 6 July 2011.

30. ̂  http://www.greentechmedia.com/articles/read/solarcity-installs-electric-car-chargers-along-cal-

highway/

31. ̂  http://www.ecofriend.org/entry/eco-tech-e-move-charging-station-fuels-just-about-everything-

with-solar-energy/

32. ̂  http://www.digitaltrends.com/cars/sanya-skypump-worlds-first-wind-powered-ev-charging-station-

debuts-in-spain/

Automated charging machineFrom Wikipedia, the free encyclopedia

This article is an orphan, as no other articles link to it. Please introduce links to this page from related articles; suggestions may be available. (July 2009)

An Automated Charging Machine (ACM) is an electronic machine that provides the public with the ability

to recharge a mobile device, often for a small fee. Similar to vending machines, ACMs take cash, then

charge the connected devices, which may be cell phones, PDAs, or other handheld devices. Usually, these

machines charge much faster than normal chargers would charge them; some provide a charge in as little

as 10 minutes.[1]

Contents

  [hide]

1   History

2   Locations

3   See also

4   References

[edit]History

Public charging stations for mobile devices appeared around 2006.[2] A variety of features have been

introduced to these machines, including lockers, UV sanitation, and wirelessly updated advertising space.

[3] Since the introduction of the idea, an increasing number of companies are looking toward ACMs for

vending and advertising revenue.

[edit]Locations

ACMs are generally deployed in areas with a high amount of foot traffic, similar to vending machines

and ATMs. These places include airports, shopping malls, parks, clubs, supermarkets,campuses, and other

popular locations. Though is it unknown how many ACMs are in use around the world, they can be found in

a variety of countries including the United States,[4] England, andChina.

Battery chargerFrom Wikipedia, the free encyclopedia

This unit charges the batteries until they reach a specific voltage and then it trickle charges the batteries until it is

disconnected.

A simple charger equivalent to an AC/DC wall adapter. It applies 300mA to the battery at all times, which will damage

the battery if left connected too long.

A battery charger is a device used to put energy into a secondary cell or rechargeable battery by forcing

an electric current through it.

The charging protocol depends on the size and type of the battery being charged. Some battery types have

high tolerance for overcharging and can be recharged by connection to a constant voltage source or a

constant current source; simple chargers of this type require manual disconnection at the end of the charge

cycle, or may have a timer to cut off charging current at a fixed time. Other battery types cannot withstand

long high-rate over-charging; the charger may have temperature or voltage sensing circuits and a

microprocessor controller to adjust the charging current, and cut off at the end of charge. A trickle charger

provides a relatively small amount of current, only enough to counteract self-discharge of a battery that is

idle for a long time. Slow battery chargers may take several hours to complete a charge; high-rate chargers

may restore most capacity within minutes or less than an hour, but generally require monitoring of the

battery to protect it from overcharge. Electric vehicles need high-rate chargers for public access; installation

of such chargers and the distribution support for them is an issue in the proposed adoption of electric cars.

Contents

  [hide]

1   Charge rate

2   Types of battery chargers

o 2.1   Simple

o 2.2   Trickle

o 2.3   Timer-based

o 2.4   Intelligent

2.4.1   Universal battery charger–analyzers

o 2.5   Fast

o 2.6   Pulse

o 2.7   Inductive

o 2.8   USB-based

o 2.9   Solar chargers

o 2.10   Motion-powered charger

3   Applications

o 3.1   Mobile phone charger

o 3.2   Battery charger for vehicles

o 3.3   Battery electric vehicle

o 3.4   Use in experiments

4   Prolonging battery life

5   See also

6   References

7   External links

[edit]Charge rate

Charge rate is often denoted as C or C-rate and signifies a charge or discharge rate equal to the capacity

of a battery in one hour.[1] For a 1.6Ah battery, C = 1.6A. A charge rate of C/2 = 0.8A would need two

hours, and a charge rate of 2C = 3.2A would need 30 minutes to fully charge the battery from an empty

state, if supported by the battery. This also assumes that the battery is 100% efficient at absorbing the

charge.

A battery charger may be specified in terms of the battery capacity or C rate; a charger rated C/10 would

return the battery capacity in 10 hours, a charger rated at 4C would charge the battery in 15 minutes. Very

rapid charging rates, 1 hour or less, generally require the charger to carefully monitor battery parameters

such as terminal voltage and temperature to prevent overcharging and damage to the cells.

[edit]Types of battery chargers

[edit]Simple

A simple charger works by supplying a constant DC or pulsed DC power source to a battery being charged.

The simple charger does not alter its output based on time or the charge on the battery. This simplicity

means that a simple charger is inexpensive, but there is a tradeoff in quality. Typically, a simple charger

takes longer to charge a battery to prevent severe over-charging. Even so, a battery left in a simple charger

for too long will be weakened or destroyed due to over-charging. These chargers can supply either a

constant voltage or a constant current to the battery.

Simple AC-powered battery chargers have much higher ripple current and ripple voltage than other kinds of

battery supplies. When the ripple current is within the battery-manufacturer-recommended level, the ripple

voltage will also be well within the recommended level. The maximum ripple current for a typical 12 V 100

Ah VRLA battery is 5 amps. As long as the ripple current is not excessive (more than 3 to 4 times the

battery-manufacturer-recommended level), the expected life of a ripple-charged VRLA battery is within 3%

of the life of a constant DC-charged battery.[2]

[edit]Trickle

Main article: Trickle charging

A trickle charger is typically a low-current (500–1,500 mA) battery charger. A trickle charger is generally

used to charge small capacity batteries (2–30 Ah). These types of battery chargers are also used to

maintain larger capacity batteries (> 30 Ah) that are typically found on cars, boats, RVs and other related

vehicles. In larger applications, the current of the battery charger is sufficient only to provide a maintenance

or trickle current (trickle is commonly the last charging stage of most battery chargers). Depending on the

technology of the trickle charger, it can be left connected to the battery indefinitely. Some battery chargers

that can be left connected to the battery without causing the battery damage are also referred to as smart

or intelligent chargers.

[edit]Timer-based

This section does not cite any references or sources. Please help improve this section by adding citations to reliable sources. Unsourced material may be challenged and removed. (June 2010)

The output of a timer charger is terminated after a pre-determined time. Timer chargers were the most

common type for high-capacity Ni-Cd cells in the late 1990s for example (low-capacity consumer Ni-Cd

cells were typically charged with a simple charger).

Often a timer charger and set of batteries could be bought as a bundle and the charger time was set to suit

those batteries. If batteries of lower capacity were charged then they would be overcharged, and if batteries

of higher capacity were charged they would be only partly charged. With the trend for battery technology to

increase capacity year on year, an old timer charger would only partly charge the newer batteries.

Timer based chargers also had the drawback that charging batteries that were not fully discharged, even if

those batteries were of the correct capacity for the particular timed charger, would result in over-charging.

[edit]Intelligent

Example of a smart charger for AA and AAA batteries

A "smart charger" should not be confused with a "smart battery". A smart battery is generally defined as

one containing some sort of electronic device or "chip" that can communicate with a smart charger about

battery characteristics and condition. A smart battery generally requires a smart charger it can

communicate with (see Smart Battery Data). A smart charger is defined as a charger that can respond to

the condition of a battery, and modify its charging actions accordingly. Some smart chargers are designed

to charge "smart" batteries. Some smart chargers are designed to charge "dumb" batteries, which lack any

internal electronic circuitry. The term "smart battery charger" is thoroughly ambiguous, since it is not clear

whether the adjective "smart" refers to the battery or only to the charger.

The output current of a smart charger depends upon the battery's state. An intelligent charger may monitor

the battery's voltage, temperature or time under charge to determine the optimum charge current and to

terminate charging.

For Ni-Cd and NiMH batteries, the voltage across the battery increases slowly during the charging process,

until the battery is fully charged. After that, the voltage decreases, which indicates to an intelligent charger

that the battery is fully charged. Such chargers are often labeled as a ΔV, "delta-V," or sometimes "delta

peak", charger, indicating that they monitor the voltage change.

The problem is, the magnitude of "delta-V" can become very small or even non-existent if (very)

high[quantify] capacity rechargeable batteries are recharged.[citation needed] This can cause even an intelligent

battery charger to not sense that the batteries are actually already fully charged, and continue charging.

Overcharging of the batteries will result in some cases. However, many so called intelligent chargers

employ a combination of cut off systems, which should prevent overcharging in the vast majority of cases.

A typical intelligent charger fast-charges a battery up to about 85% of its maximum capacity in less than an

hour, then switches to trickle charging, which takes several hours to top off the battery to its full capacity.[3]

[edit]Universal battery charger–analyzers

The most sophisticated types are used in critical applications e.g.: military or aviation batteries. These

heavy-duty automatic “intelligent charging” systems can be programmed with complex charging cycles

specified by the battery maker. The best are universal (i.e.: can charge all battery types), and include

automatic capacity testing and analyzing functions too.

[edit]Fast

Fast chargers make use of control circuitry in the batteries being charged to rapidly charge the batteries

without damaging the cells' elements. Most such chargers have a cooling fan to help keep the temperature

of the cells under control. Most are also capable of acting as standard overnight chargers if used with

standard NiMH cells that do not have the special control circuitry.

[edit]Pulse

Some chargers use pulse technology in which a series of voltage or current pulses is fed to the battery.

The DC pulses have a strictly controlled rise time, pulse width, pulse repetition rate (frequency)

and amplitude. This technology is said to work with any size, voltage, capacity or chemistry of batteries,

including automotive and valve-regulated batteries.[4] With pulse charging, high instantaneous voltages can

be applied without overheating the battery. In a Lead–acid battery, this breaks down lead-sulfate crystals,

thus greatly extending the battery service life.[5]

Several kinds of pulse charging are patented.[6][7][8] Others are open source hardware.[9]

Some chargers use pulses to check the current battery state when the charger is first connected, then use

constant current charging during fast charging, then use pulse charging as a kind of trickle charging to

maintain the charge.[10]

Some chargers use "negative pulse charging", also called "reflex charging" or "burp charging".[11] Such

chargers use both positive and brief negative current pulses. There is no significant evidence, however,

that negative pulse charging is more effective than ordinary pulse charging.[12][13]

[edit]Inductive

Main article: Inductive charging

Inductive battery chargers use electromagnetic induction to charge batteries. A charging station sends

electromagnetic energy through inductive coupling to an electrical device, which stores the energy in the

batteries. This is achieved without the need for metal contacts between the charger and the battery. It is

commonly used in electric toothbrushes and other devices used in bathrooms. Because there are no open

electrical contacts, there is no risk of electrocution.

[edit]USB-based

See also: USB#Power

Pay-per-charge kiosk, illustrating the variety of mobile phone charger connectors

Since the Universal Serial Bus specification provides for a five-volt power supply, it is possible to use a

USB cable as a power source for recharging batteries. Products based on this approach include chargers

for cellular phones and portable digital audio players. They may be fully compliant USB peripheral devices

adhering to USB power discipline, or uncontrolled in the manner of USB decorations.

[edit]Solar chargers

Further information: Solar charger and energy harvesting

Solar chargers convert light energy into DC current. They are generally portable, but can also be fixed

mount. Fixed mount solar chargers are also known as solar panels. Solar panels are often connected to the

electrical grid, whereas portable solar chargers are used off-the-grid (i.e. cars, boats, orRVs).

Although portable solar chargers obtain energy from the sun only, they still can (depending on the

technology) be used in low light (i.e. cloudy) applications. Portable solar chargers are typically used

for trickle charging, although some solar chargers (depending on the wattage), can completely recharge

batteries. The Kinesis K3 is a handheld charger for charging small personal devices like cellphones, gps's,

digital cameras, gaming devices, etc. It contains a small wind generator, a small solar panel and batteries.

The batteries can be charged by the panel, the wind generator or by connection to a power source (120V,

12V, or USB). It can then be used to recharge a small personal device.

[edit]Motion-powered charger

Several companies have begun making devices that charge batteries based on regular human motion. One

example, made by Tremont Electric, consists of a magnet held between two springs that can charge a

battery as the device is moved up and down, such as when walking. Such products have not yet achieved

significant commercial success.[14]

[edit]Applications

Since a battery charger is intended to be connected to a battery, it may not have voltage regulation or

filtering of the DC voltage output. Battery chargers equipped with both voltage regulation and filtering may

be identified as battery eliminators.

[edit]Mobile phone charger

See also: USB#Power

Micro USB mobile phone charger

A charging station for various brands of mobile phones.

Most mobile phone chargers are not really chargers, only power adapters that provide a power source for

the charging circuitry which is almost always contained within the mobile phone.[15] They are notoriously

diverse, having a wide variety of DC connector-styles and voltages, most of which are not compatible with

other manufacturers' phones or even different models of phones from a single manufacturer.

Users of publicly accessible charging kiosks must be able to cross-reference connectors with device

brands/models and individual charge parameters and thus ensure delivery of the correct charge for their

mobile device. A database-driven system is one solution, and is being incorporated into some designs of

charging kiosks.

Mobile phones can usually accept a relatively wide range of voltages[citation needed], as long as it is sufficiently

above the phone battery's voltage. However, if the voltage is too high, it can damage the phone. Mostly, the

voltage is 5 volts or slightly higher, but it can sometimes vary up to 12 volts when the power source is not

loaded.

There are also human-powered chargers sold on the market, which typically consists of a dynamo powered

by a hand crank and extension cords. There are also solar chargers.

China, the European Commission and other countries are making a national standard on mobile phone

chargers using the USB standard.[16] In June 2009, 10 of the world's largest mobile phone manufacturers

signed a Memorandum of Understanding to develop specifications for and support amicroUSB-

equipped common External Power Supply (EPS) for all data-enabled mobile phones sold in the EU.[17]

[18] On October 22, 2009, theInternational Telecommunication Union announced a standard for a universal

charger for mobile handsets (Micro-USB).[19]

[edit]Battery charger for vehicles

Further information: Charging station

There are two main types of charges for vehicles:

To recharge a fuel vehicle's starter battery, where a modular charger is used.

To recharge an electric vehicle (EV) battery pack.

[edit]Battery electric vehicle

These vehicles include a battery pack, so generally use series charger.

EV converted electric vehicle battery chargers come in a variety of brands and

characteristics. Zivan, Manzanita Micro, Elcon, Quick Charge,Rossco, Brusa, Delta-

Q, Kelly, Lester and Soneil are the top 10 EV chargers in 2011 according to EVAlbum.com. These chargers

vary from 1 KW to 7.5 KW maximum charge rate. Some use algorithm charge curves, others use constant

voltage, constant current. Some are programmable by the end user through a CAN port, some have dials

for maximum voltage and amperage, some are preset to specified battery pack voltage, amp-hour and

chemistry. Prices range from $400 to $4500.[20]

A 10 Ampere-hour battery could take 15 hours to reach a fully charged state from a fully discharged

condition with a 1 Ampere charger as it would require roughly 1.5 times the battery's capacity.

Public EV charging[21] heads (aka: stations) provide 6 kW (host power of 208 to 240 VAC off a 40 amp

circuit). 6 kW will recharge an EV roughly 6 times faster than 1 kW overnight charging.

Rapid charging results in even faster recharge times and is limited only by available AC power and the type

of charging system.[22]

On board EV chargers (change AC power to DC power to recharge the EV's pack) can be:

Isolated: they make no physical connection between the A/C electrical mains and the batteries being

charged. These typically employ some form of Inductive charging. Some isolated chargers may be

used in parallel. This allows for an increased charge current and reduced charging times. The battery

has a maximum current rating that cannot be exceeded

Non-isolated: the battery charger has a direct electrical connection to the A/C outlet's wiring. Non-

isolated chargers cannot be used in parallel.

Power Factor Correction (PFC) chargers can more closely approach the maximum current the plug can

deliver, shortening charging time.

Charge stations

Main article: Charging station

There is a list of public EV charging stations in the U.S.A. and worldwide[21]

Project Better Place is deploying a network of charging stations and subsidizing vehicle battery costs

through leases and credits.

Auxiliary charger designed to fit a variety of proprietary devices

Portable chargers comes in various capacities: 3400 – 11200 mAh

Non-contact magnetic charging

Researchers at the Korea Advanced Institute of Science and Technology (KAIST) have developed an

electric transport system (called Online Electric Vehicle, OLEV) where the vehicles get their power needs

from cables underneath the surface of the road via non-contact magnetic charging, (where a power source

is placed underneath the road surface and power is wirelessly picked up on the vehicle itself. As a possible

solution to traffic congestion and to improve overall efficiency by minimizing air resistance and so reduce

energy consumption, the test vehicles followed the power track in a convoy formation[23]

[edit]Use in experiments

A battery charger can work as a DC power adapter for experimentation. It may, however, require an

external capacitor to be connected across its output terminals in order to "smooth" the voltage sufficiently,

which may be thought of as a DC voltage plus a "ripple" voltage added to it. Note that there may be

an internal resistance connected to limit the short circuit current, and the value of that internal resistance

may have to be taken into consideration in experiments.

[edit]Prolonging battery life

What practices are best depend on the type of battery. NiCd cells need to be fully discharged occasionally,

or else the battery loses capacity over time in a phenomenon known as "memory effect". Once a month

(once every 30 charges) is sometimes recommended.[citation needed] This extends the life of the battery since

memory effect is prevented while avoiding full charge cycles which are known to be hard on all types of

dry-cell batteries, eventually resulting in a permanent decrease in battery capacity.

Most modern cell phones, laptops, and most electric vehicles use Lithium-ion batteries. These batteries last

longest if the battery is frequently charged; fully discharging them will degrade their capacity relatively

quickly.[24] When storing however, lithium batteries degrade more while fully charged than if they are only

40% charged. Degradation also occurs faster at higher temperatures. Degradation in lithium-ion batteries is

caused by an increased internal battery resistance due to cell oxidation. This decreases the efficiency of

the battery, resulting in less net current available to be drawn from the battery.[citation needed] However, if Li-ION

cells are discharged below a certain voltage a chemical reaction occurs that make them dangerous if

recharged, which is why probably all such batteries in consumer goods now have an "electronic fuse" that

permanently disables them if the voltage falls below a set level. The electronic fuse draws a small amount

of current from the battery, which means that if a laptop battery is left for a long time without charging it,

and with a very low initial state of charge, the battery may be permanently destroyed.

Internal combustion engine vehicles, such as boats, RVs, ATVs, motorcycles, cars, trucks, and more

use lead–acid batteries. These batteries employ a sulfuric acid electrolyte and can generally be charged

and discharged without exhibiting memory effect, though sulfation (a chemical reaction in the battery which

deposits a layer of sulfates on the lead) will occur over time. Keeping the electrolyte level in the

recommended range is necessary. When discharged, these batteries should be recharged immediately in

order to prevent sulfation. These sulfates are electrically insulating and therefore interfere with the transfer

of charge from the sulfuric acid to the lead, resulting in a lower maximum current than can be drawn from

the battery. all though there are methods for restoring Sulfated batteries such as a desulfation technique

called pulse conditioning, the process is difficult and or time consuming thus adding to time and cost for

maintenance, thus typically Sulfated batteries are simply replaced with new batteries and the old ones

recycled.

Lead–acid batteries will experience substantially longer life when a maintenance charger is used to "float

charge" the battery. This prevents the battery from ever being below 100% charge, preventing sulfate from

forming. Proper temperature compensated float voltage should be used to achieve the best results.[citation

needed]

References

1. ̂  A Guide to Understanding Battery Specifications, MIT Electric Vehicle Team, December 2008

2. ̂  "Effects of AC Ripple Current on VRLA Battery Life" by Emerson Network Power

3. ̂  Dave Etchells. "The Great Battery Shootout".

4. ̂  "AN913: Switch-Mode, Linear, and Pulse Charging Techniques for Li+ Battery in Mobile Phones and

PDAs". Maxim. 2001.

5. ̂  "Lead–acid battery sulfation". Archived from the original on 2007-04-02.

6. ̂  ""fast pulse battery charger" patent". 2003.

7. ̂  "Battery charger with current pulse regulation" patented 1981 United States Patent 4355275

8. ̂  "Pulse-charge battery charger" patented 1997 United States Patent 5633574

9. ̂  http://www.dallas.net/~jvpoll/Battery/aaPictures.html Pulse-charger/desulfator circuit schematic

10. ̂  "Pulse Maintenance charging."[dead link]

11. ̂  "The pulse power(tm) battery charging system"

12. ̂  "Negative Pulse Charge, or "Burp" Charging: Fact or Fiction?"

13. ̂  Tech Brief: Negative Pulse Charging Myths and Facts and Negative Pulse Charging: Myths and Facts

14. ̂  Martin LaMonica, CNET. "Motion-powered gadget charger back on track." Jul 1, 2011. Retrieved Jul

1, 2011.

15. ̂  Mobile phone battery care

16. ̂  China to work out national standard for mobile phone chargers. English.sina.com. Retrieved on 2011-

11-11.

17. ̂  "Cellphone charger harmonization". ec.europa.eu. Retrieved 2011-01-21.

18. ̂  PC World:Universal Chargers are a Good Start Jan 2009

19. ̂  Oct 22, 2009, ITU press release Universal charger for mobile phone handsets

20. ̂  EV Lithium Battery Charger Options (2011-11-19)

21. ^ a b Home. EV Charger News (2010-08-28). Retrieved on 2011-11-11.

22. ̂  Fuji Heavy Speeds Up Recharging of R1e EV. Green Car Congress (2007-09-18). Retrieved on

2011-11-11.

23. ̂  Korean electric vehicle solution. Gizmag.com. Retrieved on 2011-11-11.

24. ̂  "How to prolong lithium-based batteries". September 2006. Archived from the original on 31

December 2009. Retrieved November 21, 2009.

Förster resonance energy transferFrom Wikipedia, the free encyclopedia

Jablonski diagram of FRET with typical timescales indicated.

Förster (Fluorescence) resonance energy transfer (FRET), resonance energy transfer (RET)

or electronic energy transfer (EET), is a mechanism describing energy transfer between

two chromophores.[1] A donor chromophore, initially in its electronic excited state, may transfer energy to an

acceptor chromophore through nonradiative dipole–dipole coupling.[2] The efficiency of this energy transfer

is inversely proportional to the sixth power of the distance between donor and acceptor making FRET

extremely sensitive to small distances.[3]

Measurements of FRET efficiency can be used to determine if two fluorophores are within a certain

distance of each other.[4] Such measurements are used as a research tool in fields including biology and

chemistry.

FRET is analogous to near field communication, in that the radius of interaction is much smaller than

the wavelength of light emitted. In the near fieldregion, the excited chromophore emits a virtual photon that

is instantly absorbed by a receiving chromophore. These virtual photons are undetectable, since their

existence violates the conservation of energy and momentum, and hence FRET is known as

a radiationless mechanism. Quantum electrodynamical calculations have been used to determine that

radiationless (FRET) and radiative energy transfer are the short- and long-rangeasymptotes of a single

unified mechanism.[5][6]

Contents

  [hide]

1  Terminology

2  Theoretical basis

3  Experimental Confirmation of the Förster resonance energy transfer theory

4  Methods to measure FRET efficiency

o 4.1  Sensitized emission

o 4.2  Photobleaching FRET

o 4.3  Lifetime measurements

5  Fluorophores used for FRET

o 5.1  CFP-YFP pairs

o 5.2  BRET

o 5.3  Homo-FRET

6  Applications

7  Other methods

8  See also

9  References

10  External links

[edit]Terminology

Förster resonance energy transfer is named after the German scientist Theodor Förster.[7] When both

chromophores are fluorescent, the term "fluorescence resonance energy transfer" is often used instead,

although the energy is not actually transferred by fluorescence.[8][9] In order to avoid an erroneous

interpretation of the phenomenon that is always a nonradiative transfer of energy (even when occurring

between two fluorescent chromophores), the name "Förster resonance energy transfer" is preferred to

"fluorescence resonance energy transfer;" however, the latter enjoys common usage in scientific literature.

[10]

[edit]Theoretical basis

The FRET efficiency ( ) is the quantum yield of the energy transfer transition, i.e. the fraction of energy

transfer event occurring per donor excitation event[11]:

where   is the rate of energy transfer,   the radiative decay rate and the   are the rate

constants of any other de-excitation pathway.[12]

The FRET efficiency depends on many physical parameters that can be grouped as follows:

The distance between the donor and the acceptor

The spectral overlap of the donor emission spectrum and the acceptor absorption spectrum.

The relative orientation of the donor emission dipole moment and the acceptor absorption dipole

moment.

 depends on the donor-to-acceptor separation distance   with an inverse 6th power law due to the

dipole-dipole coupling mechanism:

with   being the Förster distance of this pair of donor and acceptor, i.e. the distance at which

the energy transfer efficiency is 50%.[12] The Förster distance depends on the overlap integral of

the donor emission spectrum with the acceptor absorption spectrum and their mutual molecular

orientation as expressed by the following equation.[13][14]

where   is the fluorescence quantum yield of the donor in the absence of the

acceptor, κ2 is the dipole orientation factor,   is the refractive index of the medium,   

is Avogadro's number, and   is the spectral overlap integral calculated as

where   is the normalized donor emission spectrum, and   is the acceptor molar

extinction coefficient.[15] κ2 =2/3 is often assumed. This value is obtained when both dyes

are freely rotating and can be considered to be isotropically oriented during the excited

state lifetime. If either dye is fixed or not free to rotate, then κ2 =2/3 will not be a valid

assumption. In most cases, however, even modest reorientation of the dyes results in

enough orientational averaging that κ2 = 2/3 does not result in a large error in the

estimated energy transfer distance due to the sixth power dependence of R0 on κ2. Even

when κ2 is quite different from 2/3 the error can be associated with a shift in R0 and thus

determinations of changes in relative distance for a particular system are still valid.

Fluorescent proteins do not reorient on a timescale that is faster than their fluorescence

lifetime. In this case 0 ≤ κ2 ≤ 4.[15]

The FRET efficiency relates to the quantum yield and the fluorescence lifetime of the

donor molecule as follows:[16]

where   and   are the donor fluorescence lifetimes in the presence and absence

of an acceptor, respectively, or as

where   and   are the donor fluorescence intensities with and without an

acceptor, respectively.

[edit]Experimental Confirmation of the Förster resonance energy transfer theory

The inverse sixth power distance dependence of Förster resonance energy

transfer was experimentally confirmed by Stryer and Haugland [17]  using a donor

and an acceptor separated on an oligoproline helix. Haugland, Yguerabide and

Stryer[18] also experimentally demonstrated the theoretical dependence of

Förster resonance energy transfer on the overlap integral by using a fused

indolosteroid as a donor and a ketone as an acceptor.

[edit]Methods to measure FRET efficiency

Example of FRET between CFP and YFP (Wavelength vs. Absorption): a fusion

protein containing CFP and YFP excited at 440nm wavelength. The fluorescent

emission peak of CFP overlaps the excitation peak of YFP. Because the two proteins

are adjacent to each other, the energy transfer is significant–a large proportion of the

energy from CFP is transferred to YFP and creates a much larger YFP emission

peak.

In fluorescence microscopy, fluorescence confocal laser scanning microscopy,

as well as in molecular biology, FRET is a useful tool to quantify molecular

dynamics in biophysics and biochemistry, such as protein-protein interactions,

protein–DNAinteractions, and protein conformational changes. For monitoring

the complex formation between two molecules, one of them is labeled with a

donor and the other with an acceptor. The FRET efficiency is measured and

used to identify interactions between the labeled complexes. There are several

ways of measuring the FRET efficiency by monitoring changes in the

fluorescence emitted by the donor or the acceptor.[19]

[edit]Sensitized emission

One method of measuring FRET efficiency is to measure the variation in

acceptor emission intensity.[14] When the donor and acceptor are in proximity

(1–10 nm) due to the interaction of the two molecules, the acceptor emission

will increase because of the intermolecular FRET from the donor to the

acceptor. For monitoring protein conformational changes, the target protein is

labeled with a donor and an acceptor at two loci. When a twist or bend of the

protein brings the change in the distance or relative orientation of the donor and

acceptor, FRET change is observed. If a molecular interaction or a protein

conformational change is dependent on ligand binding, this FRET technique is

applicable to fluorescent indicators for the ligand detection.

[edit]Photobleaching FRET

FRET efficiencies can also be inferred from the photobleaching rates of the

donor in the presence and absence of an acceptor.[14]This method can be

performed on most fluorescence microscopes; one simply shines the excitation

light (of a frequency that will excite the donor but not the acceptor significantly)

on specimens with and without the acceptor fluorophore and monitors the donor

fluorescence (typically separated from acceptor fluorescence using a bandpass

filter) over time. The timescale is that of photobleaching, which is seconds to

minutes, with fluorescence in each curve being given by

where   is the photobleaching decay time constant and depends on whether

the acceptor is present or not. Since photobleaching consists in the permanent

inactivation of excited fluorophores, resonance energy transfer from an excited

donor to an acceptor fluorophore prevents the photobleaching of that donor

fluorophore, and thus high FRET efficiency leads to a longer photobleaching

decay time constant:

where   and   are the photobleaching decay time constants of the donor

in the presence and in the absence of the acceptor, respectively. (Notice that

the fraction is the reciprocal of that used for lifetime measurements).

This technique was introduced by Jovin in 1989.[20] Its use of an entire curve of

points to extract the time constants can give it accuracy advantages over the

other methods. Also, the fact that time measurements are over seconds rather

than nanoseconds makes it easier than fluorescence lifetime measurements,

and because photobleaching decay rates do not generally depend on donor

concentration (unless acceptor saturation is an issue), the careful control of

concentrations needed for intensity measurements is not needed. It is,

however, important to keep the illumination the same for the with- and without-

acceptor measurements, as photobleaching increases markedly with more

intense incident light.

[edit]Lifetime measurements

FRET efficiency can also be determined from the change in the

fluorescence lifetime of the donor.[14] The lifetime of the donor will decrease in

the presence of the acceptor. Lifetime measurements of FRET are used

in Fluorescence-lifetime imaging microscopy.

[edit]Fluorophores used for FRET

[edit]CFP-YFP pairs

One common pair fluorophores for biological use is a cyan fluorescent

protein (CFP) – yellow fluorescent protein (YFP) pair.[21] Both are color variants

of green fluorescent protein (GFP). Labeling with organic fluorescent dyes

requires purification, chemical modification, and intracellular injection of a host

protein. GFP variants can be attached to a host protein by genetic

engineering which can be more convenient.

[edit]BRET

A limitation of FRET is the requirement for external illumination to initiate the

fluorescence transfer, which can lead to background noise in the results from

direct excitation of the acceptor or tophotobleaching. To avoid this

drawback, Bioluminescence Resonance Energy Transfer (or BRET) has been

developed.[22] This technique uses a bioluminescent luciferase (typically the

luciferase from Renilla reniformis) rather than CFP to produce an initial photon

emission compatible with YFP.

[edit]Homo-FRET

In general, "FRET" refers to situations where the donor and acceptor proteins

(or "fluorophores") are of two different types. In many biological situations,

however, researchers might need to examine the interactions between two, or

more, proteins of the same type—or indeed the same protein with itself, for

example if the protein folds or forms part of a polymer chain of proteins[23] or for

other questions of quantification in biological cells.[24]

Obviously, spectral differences will not be the tool used to detect and measure

FRET, as both the acceptor and donor protein emit light with the same

wavelengths. Yet researchers can detect differences in the polarisation

between the light which excites the fluorophores and the light which is emitted,

in a technique called FRET anisotropy imaging; the level of quantified

anisotropy (difference in polarisation between the excitation and emission

beams) then becomes an indicative guide to how many FRET events have

happened.[25]

[edit]Applications

FRET has been used to measure distance and detect molecular interactions in

a number systems and has applications in biology and chemistry.[26] FRET can

be used to measure distances between domains a single protein and therefore

to provide information about protein conformation.[27] FRET can also detect

interaction between proteins.[28] Applied in vivio in living cells, FRET has been

used to detect the location and interactions of genes and cellular structures

including intergrins and membrane proteins.[29] FRET can be used to obtain

information about metabolic or signaling pathways.[30] FRET is also used to

study lipid rafts in cell membranes.[31]

FRET and BRET are also the common tools in the study of biochemical

reaction kinetics and molecular motors.

[edit]Other methods

A different, but related, mechanism is Dexter Electron Transfer.

An alternative method to detecting protein–protein proximity is the bimolecular

fluorescence complementation (BiFC) where two halves of a YFP are fused to a

protein. When these two halves meet they form a fluorophore after about 60 s –

1 hr.[32]

Resonant energy transfer

Resonant inductive couplingFrom Wikipedia, the free encyclopedia

Resonant inductive coupling or electrodynamic induction is the near field wireless transmission

of electrical energy between two coils that are tuned to resonate at the same frequency. The

equipment to do this is sometimes called a resonant or resonance transformer. While many

transformers employ resonance, this type has a high Q and is often air cored to avoid 'iron' losses.

The two coils may exist as a single piece of equipment or comprise two separate pieces of equipment.

Resonant transfer works by making a coil ring with an oscillating current. This generates an oscillating

magnetic field. Because the coil is highly resonant, any energy placed in the coil dies away relatively

slowly over very many cycles; but if a second coil is brought near it, the coil can pick up most of the

energy before it is lost, even if it is some distance away. The fields used are predominately non-

radiative, near field (sometimes called evanescent waves), as all hardware is kept well within the 1/4

wavelength distance they radiate little energy from the transmitter to infinity.

One of the applications of the resonant transformer is for the CCFL inverter. Another application of the

resonant transformer is to couple between stages of a superheterodyne receiver, where the selectivity

of the receiver is provided by tuned transformers in the intermediate-frequency amplifiers.

[1] Resonant transformers such as the Tesla coil can generate very high voltages with or without

arcing, and are able to provide much higher current than electrostatic high-voltage generation

machines such as the Van de Graaff generator.[2] Resonant energy transfer is the operating principle

behind proposed short range wireless electricity systems such as WiTricity and systems that have

already been deployed, such as passive RFID tags and contactless smart cards.

Contents

  [hide]

1  Resonant coupling

o 1.1  Energy transfer and efficiency

o 1.2  Coupling coefficient

o 1.3  Power transfer

o 1.4  Voltage gain

o 1.5  Transmitter coils and circuitry

o 1.6  Receiver coils and circuitry

2  History

3  Comparison with other technologies

4  Regulations and safety

5  Uses

6  See also

7  External links

8  References

[edit]Resonant coupling

Basic transmitter and receiver circuits, Rs and Rr are the resistances and losses in the associated capacitors and

inductors. Ls and Lr are coupled by small coupling coefficient, usually below 0.2

Non-resonant coupled inductors, such as typical transformers, work on the principle of a primary

coil generating a magnetic field and a secondary coil subtending as much as possible of that field so

that the power passing though the secondary is as close as possible to that of the primary. This

requirement that the field be covered by the secondary results in very short range and usually

requires a magnetic core. Over greater distances the non-resonant induction method is highly

inefficient and wastes the vast majority of the energy in resistive losses of the primary coil.

Using resonance can help improve efficiency dramatically. If resonant coupling is used, each coil is

capacitively loaded so as to form a tuned LC circuit. If the primary and secondary coils are resonant at

a common frequency, it turns out that significant power may be transmitted between the coils over a

range of a few times the coil diameters at reasonable efficiency.[3]

[edit]Energy transfer and efficiency

The general principle is that if a given oscillating amount of energy (for example alternating current

from a wall outlet) is placed into a primary coil which is capacitively loaded, the coil will 'ring', and form

an oscillating magnetic field. The energy will transfer back and forth between the magnetic field in the

inductor and the electric field across the capacitor at the resonant frequency. This oscillation will die

away at a rate determined by the gain-bandwidth (Q factor), mainly due to resistive and radiative

losses. However, provided the secondary coil cuts enough of the field that it absorbs more energy

than is lost in each cycle of the primary, then most of the energy can still be transferred.

The primary coil forms a series RLC circuit, and the Q factor for such a coil is:

,

For R=10 ohm,C=1 micro farad and L=10 mH, Q is given as 10.

Because the Q factor can be very high, (experimentally around a thousand has been

demonstrated[4] with air cored coils) only a small percentage of the field has to be coupled from

one coil to the other to achieve high efficiency, even though the field dies quickly with distance

from a coil, the primary and secondary can be several diameters apart.

[edit]Coupling coefficient

The coupling coefficient is the fraction of the flux of the primary that cuts the secondary coil, and

is a function of the geometry of the system. The coupling coefficient is between 0 and 1.

Systems are said to be tightly coupled, loosely coupled, critically coupled or overcoupled. Tight

coupling is when the coupling coefficient is around 1 as with conventional iron-core transformers.

Overcoupling is when the secondary coil is so close that it tends to collapse the primary's field,

and critical coupling is when the transfer in the passband is optimal. Loose coupling is when the

coils are distant from each other, so that most of the flux misses the secondary, in Tesla coils

around 0.2 is used, and at greater distances, for example for inductive wireless power

transmission, it may be lower than 0.01.

[edit]Power transfer

Because the Q can be very high, even when low power is fed into the transmitter coil, a relatively

intense field builds up over multiple cycles, which increases the power that can be received—at

resonance far more power is in the oscillating field than is being fed into the coil, and the receiver

coil receives a percentage of that.

[edit]Voltage gain

The voltage gain of resonantly coupled coils is directly proportional to the square root of the ratio

of secondary and primary inductances.

[edit]Transmitter coils and circuitry

Unlike the multiple-layer secondary of a non-resonant transformer, coils for this purpose are often

single layer solenoids (to minimise skin effect and give improved Q) in parallel with a

suitablecapacitor, or they may be other shapes such as wave-wound litz wire. Insulation is either

absent, with spacers, or low permittivity, low loss materials such as silk to minimise dielectric

losses.

Colpitts oscillator. In resonant energy transfer the inductor would be the transmitter coil and capacitors are

used to tune the circuit to a suitable frequency.

To progressively feed energy/power into the primary coil with each cycle, different circuits can be

used. One circuit employs a Colpitts oscillator.[4]

In Tesla coils an intermittent switching system, a "circuit controller or "break," is used to inject an

impulsive signal into the primary coil; the secondary coil then rings and decays.

[edit]Receiver coils and circuitry

The receiver of a smart card has a coil connected to a chip which provides capacitance to give resonance as

well as regulators to provide a suitable voltage

The secondary receiver coils are similar designs to the primary sending coils. Running the

secondary at the same resonant frequency as the primary ensures that the secondary has a

low impedance at the transmitter's frequency and that the energy is optimally absorbed.

Example receiver coil. The coil is loaded with a capacitor and two LEDs. The coil and the capacitor form a

series LC circuit which is tuned to a resonant frequency that matches the transmission coil located inside of

the brown matt. Power is transmitted over a distance of thirteen inches.

To remove energy from the secondary coil, different methods can be used, the AC can be used

directly or rectified and a regulator circuit can be used to generate DC voltage.

[edit]History

This advanced Tesla coil was designed to implement wireless power by means of the disturbed charge of ground

and air method.

In 1894 Nikola Tesla used resonant inductive coupling, also known as "electro-dynamic induction"

to wirelessly light up phosphorescent and incandescent lamps at the 35 South Fifth Avenue

laboratory, and later at the 46 E. Houston Street laboratory in New York City.[5][6][7] In 1897 he

patented a device[8] called the high-voltage, resonance transformer or "Tesla coil." Transferring

electrical energy from the primary coil to the secondary coil by resonant induction, a Tesla coil is

capable of producing very high voltages at high frequency. The improved design allowed for the

safe production and utilization of high-potential electrical currents, "without serious liability of the

destruction of the apparatus itself and danger to persons approaching or handling it."

In the early 1960s resonant inductive wireless energy transfer was used successfully in

implantable medical devices[9] including such devices as pacemakers and artificial hearts. While

the early systems used a resonant receiver coil, later systems[10] implemented resonant

transmitter coils as well. These medical devices are designed for high efficiency using low power

electronics while efficiently accommodating some misalignment and dynamic twisting of the coils.

The separation between the coils in implantable applications is commonly less than 20 cm. Today

resonant inductive energy transfer is regularly used for providing electric power in many

commercially available medical implantable devices.[11]

Wireless electric energy transfer for experimentally powering electric automobiles and buses is a

higher power application (>10 kW) of resonant inductive energy transfer. High power levels are

required for rapid recharging and high energy transfer efficiency is required both for operational

economy and to avoid negative environmental impact of the system. An experimental electrified

roadway test track built circa 1990 achieved 80% energy efficiency while recharging the battery of

a prototype bus at a specially equipped bus stop.[12][13] The bus could be outfitted with a

retractable receiving coil for greater coil clearance when moving. The gap between the transmit

and receive coils was designed to be less than 10 cm when powered. In addition to buses the use

of wireless transfer has been investigated for recharging electric automobiles in parking spots and

garages as well.

Some of these wireless resonant inductive devices operate at low milliwatt power levels and are

battery powered. Others operate at higher kilowatt power levels. Current implantable medical and

road electrification device designs achieve more than 75% transfer efficiency at an operating

distance between the transmit and receive coils of less than 10 cm.

In 1995, Professor John Boys and Prof Grant Covic, of The University of Auckland in New

Zealand, developed systems to transfer large amounts of energy across small air gaps.[citation needed]

In 1998, RFID tags were patented that were powered in this way.[14]

In November 2006, Marin Soljačić and other researchers at the Massachusetts Institute of

Technologyapplied this near field behavior, well known in electromagnetic theory, the wireless

power transmission concept based on strongly-coupled resonators.[15][16][17] In a theoretical

analysis,[18] they demonstrate that, by designing electromagnetic resonators that suffer minimal

loss due to radiation and absorption and have a near field with mid-range extent (namely a few

times the resonator size), mid-range efficient wireless energy-transfer is possible. The reason is

that, if two such resonant circuits tuned to the same frequency are within a fraction of a

wavelength, their near fields (consisting of 'evanescent waves') couple by means of evanescent

wave coupling. Oscillating waves develop between the inductors, which can allow the energy to

transfer from one object to the other within times much shorter than all loss times, which were

designed to be long, and thus with the maximum possible energy-transfer efficiency. Since the

resonant wavelength is much larger than the resonators, the field can circumvent extraneous

objects in the vicinity and thus this mid-range energy-transfer scheme does not require line-of-

sight. By utilizing in particular the magnetic field to achieve the coupling, this method can be safe,

since magnetic fields interact weakly with living organisms.

Apple Inc. applied for a patent on the technology in 2010, after WiPower did so in 2008.[19]

[edit]Comparison with other technologies

Compared to inductive transfer in conventional transformers, except when the coils are well within

a diameter of each other, the efficiency is somewhat lower (around 80% at short range) whereas

tightly coupled conventional transformers may achieve greater efficiency (around 90-95%) and for

this reason it cannot be used where high energy transfer is required at greater distances.

However, compared to the costs associated with batteries, particularly non-rechargeable

batteries, the costs of the batteries are hundreds of times higher. In situations where a source of

power is available nearby, it can be a cheaper solution.[20] In addition, whereas batteries need

periodic maintenance and replacement, resonant energy transfer can be used instead. Batteries

additionally generate pollution during their construction and their disposal which is largely

avoided.

[edit]Regulations and safety

Unlike mains-wired equipment, no direct electrical connection is needed and hence equipment

can be sealed to minimize the possibility of electric shock.

Because the coupling is achieved using predominantly magnetic fields; the technology may be

relatively safe. Safety standards and guidelines do exist in most countries for electromagnetic

field exposures (e.g.[21][22]) Whether the system can meet the guidelines or the less stringent legal

requirements depends on the delivered power and range from the transmitter.

Deployed systems already generate magnetic fields, for example induction

cookers and contactless smart card readers.

[edit]Uses

Contactless smart card

High voltage (one million volt) sources for X-ray production[23]

Tesla coils

Some Passports

[edit]See also

Ubeam [24]

WiTricity

Wireless Resonant Energy Link  (WREL)

eCoupled  for particular implementations of this technology.

Inductance

RFID  some passive id tags are powered by radio frequency transmissions

Microwave power transmission  an alternative, much longer range way of transferring energy

Odd sympathy  similar resonances occur with mechanical pendulums

Evanescent wave coupling  essentially the same process at optical frequencies

Wardenclyffe tower

[edit]External links

IEEE Spectrum: A critical look at wireless power

Intel: Cutting the Last Cord, Wireless Power

Yahoo News: Intel cuts electric cords with wireless power system

BBC News: An end to spaghetti power cables

Instructables: wireless power

"Marin Soljačić (researcher team leader) home page on MIT" .

Jonathan Fildes (2007-06-07). "Wireless energy promise powers up". BBC News.

JR Minkel (2007-06-07). "Wireless Energy Lights Bulb from Seven Feet Away". Scientific

American.

"Breakthrough to a wireless (electricity) future (WiTricity)" . The Press Association. 2007-06-

07.

Katherine Noyes (2007-06-08). "MIT Wizards Zap Electricity Through the Air".

TechNewsWorld.

Chris Peredun, Kristopher Kubicki (2007-06-11). "MIT Engineers Unveil Wireless Power

System". DailyTech.

"Supporting Online Material for Wireless Power Transfer via Strongly Coupled Magnetic

Resonances". Science Magazine.

Gary Peterson (2008-08-06). "Anticipating Witricity". 21st Century Books.

William C. Brown biography on the IEEE MTT-S website

Anuradha Menon (2008-11-14). "Intel’s Wireless Power Technology Demonstrated". The

Future of Things e-magazine.

[edit]References

1. ̂  Carr, Joseph. Secrets of RF Circuit Design. pp. pp. 193–195}. ISBN 0-07-137067-6.

2. ̂  Abdel-Salam, M. et al.. High-Voltage Engineering: Theory and Practice. pp. 523–524. ISBN 0-

8247-4152-8.

3. ̂  Steinmetz, Dr. Charles Proteus (1914). Elementary Lectures on Electric Discharges, Waves, and

Impulses, and Other Transients (2nd ed.). McGraw-Hill.

4. ^ a b Wireless Power Transfer via Strongly Coupled Magnetic Resonances André Kurs, Aristeidis

Karalis, Robert Moffatt, J. D. Joannopoulos, Peter Fisher, Marin Soljacic

5. ̂  "Experiments with Alternating Currents of Very High Frequency and Their Application to Methods

of Artificial Illumination, AIEE, Columbia College, N.Y., May 20, 1891". 1891-06-20.

6. ̂  "Experiments with Alternate Currents of High Potential and High Frequency, IEE Address,'

London, February 1892". 1892-02-00.

7. ̂  "On Light and Other High Frequency Phenomena, 'Franklin Institute,' Philadelphia, February

1893, and National Electric Light Association, St. Louis, March 1893". 1893-03-00.

8. ̂  U.S. Patent 593,138 Electrical Transformer

9. ̂  J. C. Schuder, “Powering an artificial heart: Birth of the inductively coupled-radio frequency

system in 1960,” Artificial Organs, vol. 26, no. 11, pp. 909–915, 2002.

10. ̂  SCHWAN M. A. and P.R. Troyk, "High efficiency driver for transcutaneously coupled coils" IEEE

Engineering in Medicine & Biology Society 11th Annual International Conference, November 1989,

pp. 1403-1404.

11. ̂  "What is a cochlear implant?". Cochlearamericas.com. 2009-01-30. Retrieved 2009-06-04.

12. ̂  Systems Control Technology, Inc, "Roadway Powered Electric Vehicle Project, Track

Construction and Testing Program". UC Berkeley Path Program Technical Report: UCB-ITS-PRR-

94-07,http://www.path.berkeley.edu/PATH/Publications/PDF/PRR/94/PRR-94-07.pdf

13. ̂  Shladover, S.E., “PATH at 20: History and Major Milestones”, Intelligent Transportation Systems

Conference, 2006. ITSC '06. IEEE 2006, pages 1_22-1_29.

14. ̂  RFID Coil Design

15. ̂  "Wireless electricity could power consumer, industrial electronics". MIT News. 2006-11-14.

16. ̂  "Gadget recharging goes wireless". Physics World. 2006-11-14.

17. ̂  "'Evanescent coupling' could power gadgets wirelessly". NewScientist.com news service. 2006-

11-15.

18. ̂  Aristeidis Karalis; J.D. Joannopoulos, Marin Soljačić (2008). "Efficient wireless non-radiative mid-

range energy transfer". Annals of Physics 323: 34–

48. arXiv:physics/0611063. Bibcode 2008AnPhy.323...34K . doi:10.1016/j.aop.2007.04.017.

"Published online: April 2007"

19. ̂  "Ready for ANOTHER patent war? Apple 'invents' wireless charging."

20. ̂  "Eric Giler demos wireless electricity". TED. 2009-07. Retrieved 2009-09-13.

21. ̂  http://www.icnirp.de/documents/emfgdl.pdf ICNIRP Guidelines Guidelines for Limiting Exposure

to Time-Varying ...

22. ̂  IEEE C95.1

23. ̂  [1]

24. ̂  Ubeam