CHAPTER - 1

INTRODUCTION

The issue of calculating the energy saving amount due to regenerative

braking implementation in modern AC and DC drives is of great importance,

since it will decide whether this feature is cost effective. However, as the

increase of the electric energy cost at the industrial sector, the need for

advanced energy saving techniques emerged in order to cut down operational

costs. To this direction, this project presents a theoretical, simulation and

experimental investigation on the quantization of energy recovery due to

regenerative braking application in industrial rotating loads. Finally, a power

conversion scheme is proposed for the storage/exploitation of the recovered

energy amount.

Fossil fuels become each time less abundant and expensive, and with

the problems of worldwide pollution, they also become inadequate to be used

in such a large scale.

The automotive industry is one of the biggest spenders of this limited

resource. This fact may be changed with the use of electronic propelling

systems, such as the appliance of a three-phase induction motor driven by a

controlled inverter, replacing the internal combustion engine. The objective of

this project is to research, design and implement the most effective

regenerative system . The extra energy obtained from braking is used for light

the bulb.

1.1 BRAKING SYSTEM

All electric machines have two mechanical operations, motoring and

braking. The nature of braking can be regenerative, where the kinetic energy of

the rotor is converted into electricity and sent back to the power source or non-

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regenerative, where the source supplies electric power to provide braking. This

project investigates several critical issues related to regenerative braking in

both DC and AC electric machines, including the re generative braking

capability region and the evaluation of operating points within that capability

region that result in maximum regenerative braking recharge current. Electric

machines are used in the power trains of electric and hybrid-electric vehicles to

provide motoring or braking torque in response to the driver’s request and

power management logic. Since such vehicles carry a limited amount of

electrical energy on-board their energy storage systems (such as a battery

pack), it is important to conserve as much electrical energy as possible in order

to increase the range of travel.

Therefore, the concept of regenerative braking is of importance for such

vehicles since operating in this mode during a braking event sends power back

to the energy storage system thereby replenishing its energy level. Since the

electric machine assists the mechanical friction braking system of the vehicle,

it results in reduced wear on components within the mechanical friction brake

system. As both mechanical friction braking and electric machine braking are

used to provide the requested vehicle braking torque, braking strategies which

relate to splitting of the braking command between the two braking

mechanisms are discussed.

1.2 GENERAL DISCRIPTION

The most common form of regenerative brake involves using an electric

motor as an electric generator. In electric railways the generated electricity is

fed back into the supply system. In battery electric and hybrid electric vehicles,

the energy is stored chemically in a battery, electrically in a bank of capacitors,

or mechanically in a rotating flywheel. Hydraulic hybrid vehicles use hydraulic

motors to store energy in form of compressed air Vehicles driven by electric

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motors use the motor as a generator when using regenerative braking: it is

operated as a generator during braking and its output is supplied to an electrical

load; the transfer of energy to the load provides the braking effect.

Regenerative braking is used on hybrid gas or electric automobiles to recoup

some of the energy lost during stopping. This energy is saved in a storage

battery and used later to supply AC power.

1.3 PROJECT METHODS

This project has various different design paths to complete our product

while meeting the majority objectives. This means we will have to implement

and compare our different designs to insure the best product based on our set

of objectives. These paths have changed as we progressed through our project,

and there were a few foreseen methods that we expand upon in the design

section.

The basic design for the regenerative braking is to have an induction

motor, alternator, rectifier, battery, relay, step up transformer and load.While

an alternator is easier to find and purchase with many functioning units

available in scrap yards, they also tend to be less efficient in the output of DC

power compared to a dynamo. One option is to use two contacting wheels to

connect the two components. There are bound to be various other obstacles and

design methods to be implemented as the project progresses, and will be

observed and recorded as they occur.

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CHAPTER -2

DESIGN AND METHODOLOGY

2.1 BLOCK DIAGRAM

A simple block diagram of the overall project design is shown in Fig 2.1

Fig 2.1 Block diagram of overall project design

In our project, we consider single phase induction motor as prime

mover. Prime mover is directly coupled with an alternator by using belt and

pulley arrangement. Output of the alternator is connected to a step-up

transformer. The transformer step up into 230 V AC supply and this is fed into

an incandescent lamp.

While we applying the brake, giving DC supply to rotor. The rotor will

produce flux. Due to the kinetic energy, the rotor will slowly rotate and come

to rest. During this time an emf will produce in the stator winding and fed to

the step-up transformer and then fed to the load

The DC supply is provided with 12 V battery and this battery is charging

by using rectified output of alternator. Three phase diode bridge rectifier is

used as rectifier.

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PRIME MOVER ALTERNATOR STEP-UP

TRANSFORMER

LOAD

RECTIFIER

BATTERY

The relay circuit is used to control the braking system properly. Here we

used a 12 V single pole double throw relay.

In an ordinary system, during braking energy will lost in the form of

heat and noise. If we use this system, we can conserve the energy loss due to

braking.

2.2 PRIME MOVER

All generators, large and small, ac and dc, require a source of

mechanical power to turn their rotors. This source of mechanical energy is

called a prime mover. The type of prime mover plays an important part in the

design of alternators since the speed at which the rotor is turned determines

certain characteristics of alternator construction and operation. Here we use an

induction motor as prime mover for alternator and braking is applied to this

motor itself.

2.2.1 BELT AND PULLEY ARRANGMENT

Fig 2.2 Belt and pulley arrangement

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A pulley is a wheel on an axle or shaft that is designed to support

movement and change of direction of a cable or belt along its

circumference. Pulleys are used in a variety of ways to lift loads, apply forces,

and to transmit power. In nautical contexts, the assembly of wheel, axle, and

supporting shell is referred to as a "block."A pulley may also be called

a sheave or drum and may have a groove between two flanges around

its circumference. The drive element of a pulley system can be

a rope, cable, belt, or chain that runs over the pulley inside the groove. Hero of

Alexandria identified the pulley as one of six simple machines used to lift

weights. Pulleys are assembled to form a block and tackle in order to

provide mechanical advantage to apply large forces. Pulleys are also assembled

as part of belt and chain drives in order to transmit power from one rotating

shaft to another.

Here we use motor shaft as driver pulley and alternator shaft as driven

pulley

2.3 SINGLE PHASE INDUCTION MOTOR

An induction or asynchronous motor is an AC electric motor in which

the electric current in the rotor needed to produce torque is obtained

by electromagnetic induction from the magnetic field of the stator winding. An

induction motor therefore does not require mechanical commutation, separate-

excitation or self-excitation for all or part of the energy transferred from stator

to rotor, as in universal, DC and large synchronous motors.

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Fig 2.3 Single phase Induction Motor

Like any other electrical motor asynchronous motor also have two main

parts namely rotor and stator.

Stator: As its name indicates stator is a stationary part of induction

motor. A single phase ac supply is given to the stator of single phase induction

motor.

Rotor: The rotor is a rotating part of induction motor. The rotor is

connected to the mechanical load through the shaft. The rotor in single

phase induction motor is of squirrel cage rotor type.

The construction of single phase induction motor is almost similar to the

squirrel cage three phase motor except that in case of asynchronous motor the

stator have two windings instead of one as compare to the single stator winding

in three phase induction motor.

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2.3.1 STATOR OF SINGLE PHASE INDUCTION MOTOR

The stator of the single phase induction motor has laminated stamping to

reduce eddy current losses on its periphery. The slots are provided on its

stamping to carry stator or main winding. In order to reduce the hysteresis

losses, stamping are made up of silicon steel. When the stator winding is given

a single phase ac supply, the magnetic field is produced and the motor rotates

at a speed slightly less than the synchronous speed Ns which is given by

The construction of the stator of asynchronous motor is similar to that

of three phase induction motor except there are two dissimilarity in the

winding part of the single phase induction motor.

Firstly the single phase induction motors are mostly provided with

concentric coils. As the number of turns per coil can be easily adjusted with the

help of concentric coils, the mmf distribution is almost sinusoidal. Except for

shaded pole motor, the asynchronous motor has two stator windings namely

the main winding and the auxiliary winding. These two windings are placed in

space quadrature with respect to each other.

2.3.2 ROTOR OF SINGLE PHASE INDUCTION MOTOR

The construction of the rotor of the single phase induction motor is

similar to the squirrel cage three phase induction motor. The rotor is cylindrical

in shape and has slots all over its periphery. The slots are not made parallel to

each other but are bit skewed as the skewing prevents magnetic locking of

stator and rotor teeth and makes the working of induction motor more smooth

and quieter.

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The squirrel cage rotor consists of aluminium, brass or copper bars.

These aluminium or copper bars are called rotor conductors and are placed in

the slots on the periphery of the rotor. The rotor conductors are permanently

shorted by the copper or aluminium rings called the end rings. In order to

provide mechanical strength these rotor conductor are braced to the end ring

and hence form a complete closed circuit resembling like a cage and hence got

its name as “squirrel cage induction motor”.

As the bars are permanently shorted by end rings, the rotor electrical

resistance is very small and it is not possible to add external resistance as the

bars are permanently shorted. The absence of slip ring and brushes make the

construction of single phase induction motor very simple and robust.

2.3.3 WORKING PRINCIPLE

When single phase ac supply is given to the stator winding of single

phase induction motor, the alternating current starts flowing through the stator

or main winding. This alternating current produces an alternating flux called

main flux. This main flux also links with the rotor conductors and hence cut

the rotor conductors. According to the Faraday’s law of electromagnetic

induction, emf gets induced in the rotor. As the rotor circuit is closed one so,

the current starts flowing in the rotor. This current is called the rotor current.

This rotor current produces its own flux called rotor flux. Since this flux is

produced due to induction principle so, the motor working on this principle got

its name as induction motor. Now there are two fluxes one is main flux and

another is called rotor flux. These two fluxes produce the desired torque which

is required by the motor to rotate.

According to double field revolving theory, any alternating quantity can

be resolved into two components, each component have magnitude equal to the

half of the maximum magnitude of the alternating quantity and both these

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component rotates in opposite direction to each other. For example – a flux, φ

can be resolved into two components

Each of these components rotates in opposite direction i. e if one φm / 2

is rotating in clockwise direction then the other φm / 2 rotates in anticlockwise

direction.

When a single phase ac supply is given to the stator winding of single

phase induction motor, it produces its flux of magnitude, φm. According to the

double field revolving theory, this alternating flux, φm is divided into two

components of magnitude φm /2. Each of these components will rotate in

opposite direction, with the synchronous speed, Ns. Let us call these two

components of flux as forward component of flux, φf and backward component

of flux, φb. The resultant of these two component of flux at any instant of time,

gives the value of instantaneous stator flux at that particular instant.

Now at starting, both the forward and backward components of flux are

exactly opposite to each other. Also both of these components of flux are equal

in magnitude. So, they cancel each other and hence the net torque experienced

by the rotor at starting is zero. So, the single phase induction motors are not

self starting motors.

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2.3.4 SINGLE PHASE INDUCTION MOTOR AS SELF STARTING

MOTOR

From the above topic we can easily conclude that the single phase

induction motors are not self starting because the produced stator flux is

alternating in nature and at the starting the two components of this flux cancel

each other and hence there is no net torque. The solution to this problem is that

if the stator flux is made rotating type, rather than alternating type, which

rotates in one particular direction only. Then the induction motor will become

self starting. Now for producing this rotating magnetic field we require two

alternating flux, having some phase difference angle between them. When

these two fluxes interact with each other they will produce a resultant flux.

This resultant flux is rotating in nature and rotates in space in one particular

direction only. Once the motor starts running, the additional flux can be

removed. The motor will continue to run under the influence of the main flux

only. Depending upon the methods for making asynchronous motor as Self

Starting Motor, there are mainly four types of single phase induction

motor namely,

Split phase induction motor,

Capacitor start inductor motor,

Capacitor start capacitor run induction motor,

Shaded pole induction motor.

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2.3.5 CAPACITOR START INDUCTION MOTOR

This motor is similar to the three-phase motor except that it has only two

windings (a-a′ and b-b′) on its stator displaced 90° from each other. The a-a′

winding is connected directly to the single-phase supply. For starting, the b-b′

winding (commonly called the auxiliary winding) is connected through a

capacitor (a device that stores electric charge) to the same supply. The effect of

the capacitor is to make the current entering the winding b-b′ lead the current

in a-a′ by approximately 90°, or one-quarter of a cycle, with the rotor at

standstill. Thus, the rotating field and the starting torque are provided.

Fig 2.4 Internal Diagram of Capacitor Start Induction Motor

As the motor speed approaches its rated value, it is no longer necessary

to excite the auxiliary winding to maintain the rotating field. The currents

produced in the rotor squirrel-cage bars as they pass the winding a-a′ are

retained with negligible change as they rotate past the winding b-b′. The rotor

can continue to generate the rotating field with only winding a-a′connected.

The winding b-b′ is usually disconnected by a centrifugal switch that opens

when the speed is about 80 percent of rated value.

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Power ratings for these capacitor-start induction motors are usually

restricted to about two kilowatts for a 120-volt supply and 10 kilowatts for a

230-volt supply because of the limitations on voltage drop in the supply lines,

which would otherwise occur on starting. Typical values of synchronous speed

on a 60-hertz supply are 1,800 or 1,200 revolutions per minute for four- and

six-pole motors, respectively. Lower-speed motors can be constructed with

more poles but are less common.

The efficiency of the motor can be somewhat increased and the line

current decreased by the use of two capacitors, only one of which is taken out

of the circuit (by means of a centrifugal switch) as the rated speed is

approached. The remaining capacitor continues to provide a leading current to

phase b-b′, approximating a two-phase supply. This arrangement is known as a

capacitor-start, capacitor-run motor.

Capacitor induction motors are widely used for heavy-duty applications

requiring high starting torque. Examples are refrigerator compressors, pumps,

and conveyor.

2.4 ALTERNATOR

An alternator is an electrical generator that converts mechanical energy

to electrical energy in the form of alternating current. For reasons of cost and

simplicity, most alternators use a rotating magnetic field with a

stationary armature. 

Occasionally, a linear alternator or a rotating armature with a stationary

magnetic field is used. In principle, any AC electrical generator can be called

an alternator, but usually the term refers to small rotating machines driven by

automotive and other internal combustion engines. An alternator that uses

a permanent magnet for its magnetic field is called a magneto.

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Alternators in power stations driven by steam turbines are called turbo-

alternators. A conductor moving relative to a magnetic field develops

an electromotive force (EMF) in it, (Faraday's Law). This emf reverses its

polarity when it moves under magnetic poles of opposite polarity. Typically, a

rotating magnet, called the rotor turns within a stationary set of conductors

wound in coils on an iron core, called the stator. The field cuts across the

conductors, generating an induced EMF (electromotive force), as the

mechanical input causes the rotor to turn. The rotating magnetic field induces

an AC voltage in the stator windings. Since the currents in the stator windings

vary in step with the position of the rotor, an alternator is a synchronous

generator. The rotor's magnetic field may be produced by permanent magnets,

or by a field coil electromagnet. Automotive alternators use a rotor winding

which allows control of the alternator's generated voltage by varying the

current in the rotor field winding.

Permanent magnet machines avoid the loss due to magnetizing current

in the rotor, but are restricted in size, due to the cost of the magnet material.

Since the permanent magnet field is constant, the terminal voltage varies

directly with the speed of the generator. Brushless AC generators are usually

larger machines than those used in automotive applications.

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2.4.1 ALTERNATOR COMPONENTS

A typical rotating-field ac generator consists of an alternator and a

smaller dc generator built into a single unit. The output of the alternator section

supplies alternating voltage to the load. The only purpose for the dc exciter

generator is to supply the direct current required to maintain the alternator

field. This dc generator is referred to as the exciter. A typical alternator is

shown in fig

Fig 2.5 AC generator schematic drawings.

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Main parts of the alternator obviously consist of stator and rotor. But, the unlike other machines, in most of the alternators, field exciters are rotating and the armature coil is stationary.

Stator: Unlike in DC machine stator of an alternator is not meant to

serve path for magnetic flux. Instead, the stator is used for holding armature

winding. The stator core is made up of lamination of steel alloys or magnetic

iron, to minimize the losses. Armature winding is stationary in an alternator

because;

At high voltages, it easier to insulate stationary armature winding, which

may be as high as 30 kV or more.

The high voltage output can be directly taken out from the stationary

armature. Whereas, for a rotary armature, there will be large brush contact

drop at higher voltages, also the sparking at the brush surface will occur.

Field exciter winding is placed in rotor, and the low dc voltage can be

transferred safely.

The armature winding can be braced well, so as to prevent deformation

caused by the high centrifugal force.

Rotor:  There are two types of rotor used in an AC generator / alternator:

(i) Salient and (ii) Cylindrical type

Salient pole type: Salient pole type rotor is used in low and medium

speed alternators. Construction of AC generator of salient pole type

rotor is shown in the figure above. This type of rotor consists of large

number of projected poles (called salient poles), bolted on a magnetic

wheel. These poles are also laminated to minimize the eddy current

losses. Alternators featuring this type of rotor are large in diameters and

short in axial length.

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Cylindrical type: Cylindrical type rotors are used in high speed

alternators, especially in turbo alternators. This type of rotor consists of

a smooth and solid steel cylinder havingg slots along its outer periphery.

Field windings are placed in these slots.

The armature is wound for a three-phase output. Remember, a voltage is

induced in a conductor if it is stationary and a magnetic field is passed across

the conductor, the same as if the field is stationary and the conductor is moved.

The alternating voltage in the ac generator armature windings is connected

through fixed terminals to the ac load.

2.5 VOLTAGE REGULATOR

Fig 2.6 Alternator with voltage regulator

A voltage regulator circuit for an alternator includes voltage responsive

circuitry having a zener diode. The regulator will maintain a pre-determined

charging system voltage level. When the system voltage decreases the

regulator strengthens the magnetic field and thereby increases the alternator

output voltage. When the system voltage increases the regulator weakens the

magnetic field and thereby decreases the alternator output voltage.

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Zener diodes are especially used on applications with sensitive

electronic components. These can prevent major damage caused by voltage

peaks due to sudden discharges. In 12V systems, Zener diodes with a voltage

range 24V - 32V are used and in 28V systems the range is 36V - 44V.

When ac generators are operated in parallel, frequency and voltage must

both be equal. Where a synchronizing force is required to equalize only the

voltage between dc generators, synchronizing forces are required to equalize

both voltage and speed (frequency) between ac generators. On a comparative

basis, the synchronizing forces for ac generators are much greater than for dc

generators. When ac generators are of sufficient size and are operating at

unequal frequencies and terminal voltages, serious damage may result if they

are suddenly connected to each other through a common bus. To avoid this, the

generators must be synchronized as closely as possible before connecting them

together.

The output voltage of an alternator is best controlled by regulating the

voltage output of the dc exciter, which supplies current to the alternator rotor

field. This is accomplished as shown in Fig 2.5, by a zener diode regulator of a

28 volt system connected in the field circuit of the exciter. The zener diode

regulator controls the exciter field current and thus regulates the exciter output

voltage applied to the alternator field.

The only difference between the dc system and the ac system is that the

voltage coil receives its voltage from the alternator line instead of the dc

generator. In this arrangement, a three phase, step down transformer connected

to the alternator voltage supplies power to a three phase, full wave rectifier.

The 28 volt, dc output of the rectifier is then applied to the zener diode voltage

regulator. Changes in alternator voltage are transferred through the transformer

rectifier unit to the zener diode. This controls the exciter field current and the

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exciter output voltage. The exciter voltage antihunting or damping transformer

is similar to those in dc systems and performs the same function.

The DC output voltage from the half or full-wave rectifiers contains

ripple superimposed onto the DC voltage and that as the load value changes so

to does the average output voltage. By connecting a simple zener stabilizer

circuit as shown below across the output of the rectifier, a more stable output

voltage can be produced.

2.5.1 ZENER DIODE REGULATOR

Fig 2.7 Zener Diode Regulator

Zener Diodes can be used to produce a stabilized voltage output with

low ripple under varying load current conditions. By passing a small current

through the diode from a voltage source, via a suitable current limiting resistor,

the zener diode will conduct sufficient current to maintain a voltage drop of

output voltage.

The resistor, RS is connected in series with the zener diode to limit the

current flow through the diode with the voltage source, VS being connected

across the combination. The stabilized output voltage Vout is taken from across

the zener diode. The zener diode is connected with its cathode terminal

connected to the positive rail of the DC supply so it is reverse biased and will

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be operating in its breakdown condition. Resistor RS is selected so to limit the

maximum current flowing in the circuit.

With no load connected to the circuit, the load current will be zero,

( IL = 0 ), and all the circuit current passes through the zener diode which in turn

dissipates its maximum power. Also a small value of the series resistor RS will

result in a greater diode current when the load resistance RL is connected and

large as this will increase the power dissipation requirement of the diode so

care must be taken when selecting the appropriate value of series resistance so

that the zener’s maximum power rating is not exceeded under this no-load or

high-impedance condition.

The load is connected in parallel with the zener diode, so the voltage

across RL is always the same as the zener voltage, ( VR = VZ ). There is a minimum

zener current for which the stabilization of the voltage is effective and the

zener current must stay above this value operating under load within its

breakdown region at all times. The upper limit of current is of course

dependent upon the power rating of the device. The supply voltage VS must be

greater than VZ.

One small problem with zener diode stabilizer circuits is that the diode

can sometimes generate electrical noise on top of the DC supply as it tries to

stabilize the voltage. Normally this is not a problem for most applications but

the addition of a large value decoupling capacitor across the zener’s output

may be required to give additional smoothing.

Then to summarize a little. A zener diode is always operated in its

reverse biased condition. A voltage regulator circuit can be designed using a

zener diode to maintain a constant DC output voltage across the load in spite of

variations in the input voltage or changes in the load current. The zener voltage

regulator consists of a current limiting resistor RS connected in series with the

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input voltage VS with the zener diode connected in parallel with the load  RL in

this reverse biased condition. The stabilized output voltage is always selected

to be the same as the breakdown voltage VZ of the diode.

2.6 RECTIFIER

Rectifier is an electrical device that converts alternating current (AC),

which periodically reverses direction, to direct current (DC), which flows in

only one direction. The process is known as rectification. Physically, rectifiers

take a number of forms, including vacuum tube diodes, mercury-arc valves,

copper and selenium oxide rectifiers, semiconductor diodes, silicon-controlled

rectifiers and other silicon-based semiconductor switches. Historically, even

synchronous electromechanical switches and motors have been used. Early

radio receivers, called crystal radios, used a "cat's whisker" of fine wire

pressing on a crystal of galena (lead sulfide) to serve as a point-contact rectifier

or "crystal detector".

Rectifiers have many uses, but are often found serving as components of

DC power supplies and high-voltage direct current power transmission

systems. Rectification may serve in roles other than to generate direct current

for use as a source of power.

Because of the alternating nature of the input AC sine wave, the process

of rectification alone produces a DC current that, though unidirectional,

consists of pulses of current. Many applications of rectifiers, such as power

supplies for radio, television and computer equipment, require

a steady constant DC current (as would be produced by a battery). In these

applications the output of the rectifier is smoothed by an electronic

filter (usually a capacitor) to produce a steady current.

Rectifier circuits may be single-phase or multi-phase (three being the

most common number of phases). Most low power rectifiers for domestic

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equipment are single-phase, but three-phase rectification is very important for

industrial applications and for the transmission of energy as DC (HVDC).

2.6.1 THREE PHASE DIODE RECTIFIER

Single-phase rectifiers are commonly used for power supplies for

domestic equipment. However, for most industrial and high-power

applications, three-phase rectifier circuits are the norm. As with single-phase

rectifiers, three-phase rectifiers can take the form of a half-wave circuit, a full-

wave circuit using a center-tapped transformer, or a full-wave bridge circuit.

Fig 2.8 –Three phase AC full-wave rectifier

A rectifier is an electrical device that converts alternating current (AC),

which periodically reverses direction, to direct current (DC), which flows in

only one direction. The process is known as rectification. Physically, rectifiers

take a number of forms, including vacuum tube diodes, mercury-arc valves,

copper and selenium oxide rectifiers, semiconductor diodes, silicon-controlled

rectifiers and other silicon-based semiconductor switches. Historically, even

synchronous electromechanical switches and motors have been used. Early

radio receivers, called crystal radios, used a "cat's whisker" of fine wire

pressing on a crystal of galena (lead sulfide) to serve as a point-contact rectifier

or "crystal detector". Rectifiers have many uses, but are often found serving as

22

components of DC power supplies and high-voltage direct current power

transmission systems. Rectification may serve in roles other than to generate

direct current for use as a source of power. As noted, detectors of radio signals

serve as rectifiers. In gas heating systems flame rectification is used to detect

presence of a flame. Because of the alternating nature of the input AC sine

wave, the process of rectification alone produces a DC current that, though

unidirectional, consists of pulses of current. Many applications of rectifiers,

such as power supplies for radio, television and computer equipment, require

a steady constant DC current (as would be produced by a battery). In these

applications the output of the rectifier is smoothed by an electronic

filter (usually a capacitor) to produce a steady current. A more complex

circuitry device that performs the opposite function, converting DC to AC, is

called an inverter

For a three-phase full-wave diode rectifier, the ideal, no-load average

output voltage is

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2.6.2 RECTIFIER OPERATION

Fig 2.9 rectification circuit

• Two diodes are connected to each stator lead. One positive the other

negative.

• Because a single diode will only block half the the AC voltage.

• Six or eight diodes are used to rectify the AC stator voltage to DC

voltage.

• Diodes used in this configuration will redirect both the positive and

negative polarity signals of the AC voltage to produce DC voltage. This

process is called ‘Full - Wave Rectification’.

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At first you can see current pass through to the rectifier as it goes to the

battery. In the second, you can see the return path. Now, current passes through

to the rectifier however, this time current has the opposite polarity. In second

circuit you can see the new return path. Even though it enters the rectifier at a

different location, current goes to the battery in the same direction.

2.7 BATTERY

Battery is essential to supply DC power for the alternator rotor and for

the storage of generated power. An electric battery is a device consisting of

one or more electrochemical cells that convert stored chemical energy into

electrical energy. Each cell contains a positive terminal, or cathode, and a

negative terminal, or anode. Electrolytes allow ions to move between the

electrodes and terminals, which allows current to flow out of the battery to

perform work. Battery we used is 12V, 10 Ah rating.

Fig 2.10 Internal diagram of lead acid battery

25

The battery is a two-terminal device that provides DC supply to the

inverter section when the AC mains are not available. This DC is then

converted into 220V AC supply and output at the inverter output socket. It is

pertinent to state that lead-acid batteries used in automobiles are very good for

this purpose as they provide good quality power for a long duration and can be

recharged once the power stored in them are consumed. The backup time

provided by the inverter depends on the battery type and its current capacity

Primary (single-use or "disposable") batteries are used once and

discarded; the electrode materials are irreversibly changed during discharge.

Common examples are the alkaline battery used for flashlights and a multitude

of portable devices. Secondary (rechargeable batteries) can be discharged

and recharged multiple times; the original composition of the electrodes can be

restored by reverse current. Examples include the lead-acid batteries used in

vehicles and lithium ion batteries used for portable electronics.

The battery was selected based on the amount of time we wanted to

operate the system at full load. As mentioned in the specifications, we wanted

to be able to power the lights. Fulfilling the 12 V DC battery requirements, we

found a unit from Universal Battery with 18 Ah. If the battery is discharged to

50% at most, this battery leaves us with 9 Ah.

Our load of lighting, music, and an iPod charger uses about 20 watts, but

with an alternative appliance connected (e.g. phone), the total power consumed

could be estimated at 25 watts. With a 12 VDC battery and a 25 W load, we

have about 2 A of current, which gives us about 4.5 hours of use at full load –

this is consistent with our design specifications. The exact battery we selected

is UB12180 (12V 10Ah). An electric battery is a device consisting of one or

more electrochemical cells that convert stored chemical energy into electrical

energy. Each cell contains a positive terminal, or cathode, and a negative

26

terminal, or anode. Electrolytes allow ions to move between the electrodes and

terminals, which allows current to flow out of the battery to perform work.

A lead-acid battery charger is most popular though it will very large size

than others battery type. But them have advantage are : cheap, easy to buy and

long life if correctly uses.

2.7.1 CHARGING AND DISCHARGING

Over charging with high charging voltages generates

oxygen and hydrogen gas by electrolysis of water, which is lost to the cell.

Periodic maintenance of lead-acid batteries requires inspection of the

electrolyte level and replacement of any water that has been lost. Due to

the freezing-point depression of the electrolyte, as the battery discharges and

the concentration of sulfuric acid decreases, the electrolyte is more likely to

freeze during winter weather when discharged.

Fig 2.11 Fully discharged: two identical lead sulfate plates

In the discharged state both the positive and negative plates

become lead (II) sulfate (PbSO4), and the electrolyte loses much of its

dissolved sulfuric acid and becomes primarily water. The discharge process is

driven by the conduction of electrons from the negative plate back into the cell

at the positive plate in the external circuit.

27

2.7.2 ION MOTION

During discharge, H+ produced at the negative plates moves into

the electrolyte solution and then is consumed into the positive plates,

while HSO−4 is consumed at both plates. The reverse occurs during charge.

This motion can be by electrically driven proton flow or Grotthuss mechanism,

or by diffusion through the medium, or by flow of a liquid electrolyte medium.

Since the density is greater when the sulfuric acid concentration is higher, the

liquid will tend to circulate by convection. Therefore a liquid-medium cell

tends to rapidly discharge and rapidly charge more efficiently than an

otherwise similar gel cell.

2.7.3 BATTERY CHARGER

A battery charger is a device used to put energy into a cell or

(rechargeable) battery by forcing an electric current through it. Lead-acid

battery chargers typically have two tasks to accomplish. The first is to restore

capacity, often as quickly as practical. The second is to maintain capacity by

compensating for self discharge.

In both instances optimum operation requires accurate sensing of battery

voltage. When a typical lead-acid cell is charged, lead sulphate is converted to

lead on the battery’s negative plate and lead dioxide on the positive plate.

Over-charge reactions begin when the majority of lead sulphate has been

converted, typically resulting in the generation of hydrogen and oxygen gas. At

moderate charge rates, most of the hydrogen and oxygen will recombine in

sealed batteries. In unsealed batteries however, dehydration will occur. The

onset of over-charge can be detected by monitoring battery voltage.

28

Over charge reactions are indicated by the sharp rise in cell voltage. The

point at which over-charge reactions begin is dependent on charge rate, and as

charge rate is increased, the percentage of returned capacity at the onset of

over-charge diminishes. For overcharge to coincide with 100% return of

capacity, the charge rate must typically be less than 1/100 amps of its amp-

hour capacity. At high charge rates, controlled over-charging is typically as

quickly as possible. To maintain capacity on a fully charged battery, a constant

voltage is applied. The voltage must be high enough to compensate for self

discharge, yet not too high as to cause excessive over-charging.

2.8 RELAY

A relay is an electrically operated switch. Many relays Automotive-style

miniature relay, dust cover is taken off use an electromagnet to mechanically

operate a switch, but other operating principles are also used, such as solid

state relays. Relays are used where it is necessary to control a circuit by a low-

power signal (with complete electrical isolation between control and controlled

circuits), or where several circuits must be controlled by one signal. The first

relays were used in long distance telegraph circuits as amplifiers: they repeated

the signal coming in from one circuit and re-transmitted it on another circuit.

Relays were used extensively in telephone exchanges and early computers to

perform logical operations. A type of relay that can handle the high power

required to directly control an electric motor or other loads is called a

contactor. Solid-state relays control power circuits with no moving parts,

instead using a semiconductor device to perform switching. Relays with

calibrated operating characteristics and sometimes multiple operating coils are

used to protect electrical circuits from overload or faults.

29

Fig2.12 Relay

2.9 CAPACITOR-INPUT FILTER

The capacitor-input filter, also called the pi filter due to its shape that

looks like the Greek letter π, is a type of electronic filter. Filter circuits are

used to remove unwanted or undesired frequencies from a signal .A simple pi

filter, containing a pair of capacitors, an inductor, and a load .A typical

capacitor input filter consists of a filter or reservoir capacitor C1, connected

across the rectifier output, an inductor L, in series and another filter or

smoothing capacitor, C2, connected across the load, RL. A filter of this sort is

designed for use at a particular frequency, generally fixed by the AC line

frequency and rectifier configuration. When used in this service, filter

performance is often characterized by its regulation and ripple.

1. The capacitor C1 offers low reactance to the AC component of the rectifier

output while it offers infinite resistance to the DC component. As a result the

capacitor shunts an appreciable amount of the AC component while the DC

component continues its journey to the inductor L.

2. The inductor L offers high reactance to the AC component but it offers

almost zero resistance to the DC component. As a result the DC component

30

flows through the inductor while the AC component is blocked.

3. The capacitor C2 bypasses the AC component which the inductor had

failed to block. As a result only the DC component appears across the load RL.

The component value for the inductor can be estimated as an inductance that

resonates the smoothing capacitor(s) at or below one tenth of the minimum AC

frequency in the power supplied to the filter (100 Hz from a full-wave rectifier

in a region where the power supply is 50Hz). Thus if reservoir and smoothing

capacitors of 2200 microfarads are used, a suitable minimum value for the

inductor would be that which resonates 2200 microfarads (μF) to 10 Hz, i.e.

115 mH. A larger value is preferable provided the inductor can carry the

required supply current. In general, the relationship between the resonant

frequency (in hertz), which should be less than or equal to one tenth of the

minimum AC frequency, in this case 100 Hz, the capacitance (in farads), and

the inductance (in henries) can be characterized by the following resonance

equation: f_0 = {1 \over {2 \pi \sqrt{LC}}}.Comparison with other filters

Capacitor input filters can provide extremely pure DC supplies, but have fallen

out of favour because inductors tend to be unavoidably heavy, which has led to

the often-preferred choice of voltage regulators instead.

31

Fig 2.13 Capacitor-Input Filter

Fig 2.14 Capacitor-Input Filter -Charging and Discharging

32

Advantages of pi filters:

More output voltage

Ripple-free output

Disadvantages of pi filters:

Large size

Heavy

High cost

2.10 STEP-UP TRANSFORMER

The output of the alternator is 12V ac supply with a frequency of 50

Hz . This Ac supply is step up to 230 V by using step-up transformer.

The Voltage Transformer can be thought of as an electrical component rather

than an electronic component. A transformer basically is very simple static (or

stationary) electro-magnetic passive electrical device that works on the

principle of Faraday’s law of induction by converting electrical energy from

one value to another.

On a step-up transformer there are more turns on the secondary coil than

the primary coil. The induced voltage across the secondary coil is greater than

the applied voltage across the primary coil or in other words the voltage has

been “stepped-up”.

33

Fig 2.15 Step up transformer

The transformer does this by linking together two or more electrical

circuits using a common oscillating magnetic circuit which is produced by the

transformer itself. A transformer operates on the principals of “electromagnetic

induction”, in the form of  Mutual Induction. Mutual induction is the process

by which a coil of wire magnetically induces a voltage into another coil located

in close proximity to it. Then we can say that transformers work in the

“magnetic domain”, and transformers get their name from the fact that they

“transform” one voltage or current level into another.

Transformers are capable of either increasing or decreasing the voltage

and current levels of their supply, without modifying its frequency, or the

amount of electrical power being transferred from one winding to another via

the magnetic circuit.

A single phase voltage transformer basically consists of two electrical

coils of wire, one called the “Primary Winding” and another called the

“Secondary Winding”. We will define the “primary” side of the transformer as

the side that usually takes power and the “secondary” as the side that usually

34

delivers power. In a single-phase voltage transformer the primary is usually the

side with the higher voltage.

These two coils are not in electrical contact with each other but are

instead wrapped together around a common closed magnetic iron circuit called

the “core”. This soft iron core is not solid but made up of individual

laminations connected together to help reduce the core’s losses.

The two coil windings are electrically isolated from each other but are

magnetically linked through the common core allowing electrical power to be

transferred from one coil to the other. When an electric current passed through

the primary winding, a magnetic field is developed which induces a voltage

into the secondary winding .The output of the transformer is 230 V, 50

Hz ,single phase AC, which is fed to the load.

35

CHAPTER- 3

LITERATURE REVIEW

3.1 A BRIEF HISTORY REGENERATIVE BRAKING

Regenerative Braking for an Electric Vehicle Using Ultra capacitors and

a Buck-Boost Converter: An ultra capacitor bank control system for an Electric

Vehicle has been simulated. The purpose of this device is to allow higher

accelerations and decelerations of the vehicle with minimal loss of energy, and

minimal degradation of the main battery pack. The system uses an IGBT Buck-

Boost converter, which is connected to the ultra capacitor bank at the Boost

side, and to the main battery at the Buck side. The control of the system

measures the battery voltage, the battery state-of-charge, the car speed, the

instantaneous currents in both the terminals (load and ultra capacitor), and the

actual voltage of the ultra capacitor. This last indication allows to know the

amount of energy stored in the ultra capacitor. A microcomputer control

manipulates all the variables and generates the PWM switching pattern of the

IGBTs. When the car runs at high speeds, the control keeps the capacitor

discharged. If the car is not running, the capacitor bank remains charged at full

voltage. Medium speeds keep the ultra capacitors at medium voltages, to allow

future accelerations or decelerations. The battery voltage is an indication of the

car instantaneous situation. When the vehicle is accelerating, the battery

voltage goes down, which is an indication for the control to take energy from

the ultra capacitor. In the opposite situation(regenerative braking), the battery

voltage goes up, and then the control needs to activate the Buck converter to

store the kinetic energy of the vehicle inside the ultra capacitor. The

measurement of the currents in both sides allows to keep the current levels

inside maximum ratings. The battery state-of charge is used to change the

36

voltage level of the ultra capacitor at particular values. If the battery is fully

charged, the voltage level of the capacitors is kept at lower levels than when

the battery is partially discharged. The converter also has an IGBT controlled

power resistor, which allows to drop energy when in some extreme situations

cannot be accepted neither for the ultra capacitors nor for the battery pack. The

car that will be used for future implementation of this experiment is a

Chevrolet LUV truck, similar in shape and size to a Chevrolet S-10. This

vehicle was already converted to an electric car at the Catholic University of

Chile.

Fully Regenerative braking and Improved Acceleration for Electrical

Vehicles:Generally, car brake systems use hydraulic brake technology, which

converts the excess of kinetic energy into heat, effectively resulting in an

energy loss. Regenerative braking technology focuses on converting this

kinetic energy of the decelerating vehicle back into electrical energy that can

then be reused for example during acceleration. Current hybrid vehicles are

equipped with such regenerative braking technology, which makes them

particularly interesting for situations with frequent deceleration, like city

traffic. However, the technology used in these vehicles has its limitations and

therefore does not stand on its own, but is always assisted with conventional

hydraulic brakes. This paper looks at removing this limitation and allowing a

vehicle to fully rely on regenerative braking technology to deal with any

braking situation ranging from simple slow down to emergency stops. To

enable this, multiple generators with different gear ratios are used. The

additional benefit of this construction is that, by introducing the appropriate

control circuit, the generators can be used as electrical engines. Since these

motors are connected with different gear ratios there is a more consistent

acceleration at any speed. The paper shows that the overall efficiency of the

37

system is very close to the efficiency of the generators used while achieving

braking performance similar to conventional braking mechanisms.

Study on Regenerative Braking of Electric Vehicle: In this paper, a

control scheme for a constant regenerative current is given based on the

analysis of several regenerative braking schemes. The three main control

strategies discussed are maximum regenerative efficiency control, maximum

regenerative power control and the constant regenerative current control.

Analysis is performed for two modes, the continuous current mode and the

discrete current mode. Using the above analysis, a formula for regenerative

efficiency of a control scheme is derived. The analysis of the braking system is

done to find out two aspects, the electric loop efficiency and the regenerative

energy efficiency. Using the results of the analysis, the paper concludes that

the constant regenerative current control scheme is better than the maximum

regenerative power control scheme and the maximum regenerative efficiency

control scheme. Also, the paper concludes that the used method gives a higher

regenerative braking efficiency and better control performance.

Regenerative Braking for Electric Vehicle based on Fuzzy Logic

Control Strategy: In this paper to recycle more energy during regenerative

braking, a regenerative braking force calculation controller is designed based

on fuzzy logic. Here, Sugeno's fuzzy logic controller is used which has 3

inputs and the output is the braking force. The three inputs are vehicle speed;

driver’s braking requirements and the battery’s state of charge. Fuzzy

membership functions are defined for the above inputs and outputs and the

output is found out in the range of 0 to 1. Each input has a membership value

of high, medium and low based on which the fuzzy rules are developed. The

simulations which are carried out show a substantial improvement in energy

efficiency of an electric vehicle.

Benchmarking of Regenerative Braking for a Fully Electric Car:

38

Short range of electric vehicles is one of the stumbling blocks in the way of

electric cars to gaining wide user acceptance and becoming a major market

player. The possibility to recover vehicle energy otherwise lost as heat during

braking is an inherent advantage of a hybrid electric or a fully electric vehicle.

Regeneration has the potential to answer this problem by aiding in range

extension with recuperation of vehicle energy during braking. The control and

dynamics of braking undergoes a major change as compared to a conventional

vehicle with friction braking, due to the addition of motor-generator. In this

research two regenerative braking concepts namely serial and parallel have

been studied and implemented on an electric vehicle. Also a point of interest is

to find if any additional states are required from the TNO Vehicle state

estimator (VSE) which would aid in regeneration. From the results obtained

we try to draw a conclusion on the difference in energy recuperation level in

the two strategies with consistent pedal feel in mind. The proposed brake

torque distribution strategy has been tested through the simulation on the New

European Driving Cycle (NEDC) drive cycle and straight line braking

scenario. Care has been taken to observe and adjust brake torque such that

wheel lock up is prevented and hence regeneration is un-interrupted. The

research couldn’t come with any additional parameters to be added to VSE.

However, it would be worthwhile to employ VSE to achieve a more accurate

estimation of the braking force, which may aid in prolonging regeneration time

and hence more energy recuperation. The results provide a good case to invest

more time and money into developing serial regenerative braking as it clearly

out-performs parallel regenerative braking strategy. The simulation tests

conducted in this research are for a longitudinal braking scenario. Further

investigation is required to study effects with lateral motion and cornering

manoeuvres

39

A Flywheel Regenerative Braking System : This thesis presents a flywheel

based mechanical regenerative braking system (RBS) concept for a Formula

SAE type race car application, to improve the performance and/or efficiency of

the race car. A mechanical system is chosen to eliminate losses related to

energy conversion while capturing the rotational braking energy. The

Flywheel-Regenerative Braking System (f-RBS) concept consists of a metal

flywheel design of truncated cone geometry for the energy storage system

(ESS) component and a V-belt CVT with a fixed gear for the transmission

component of the RBS system. Race car lap data and race car specifications

are used for designing/sizing the components. Mathematical models are

developed for design, integration and operation of the f-RBS system. It was

observed that a maximum of 27 % of energy requirements of the race car can

be supplied by the f-RBS. Also, a Virtual test rig model is created using MSC

ADAMS, an advanced dynamics/virtual prototyping software, in order to test

the whole f-RBS system for performance, as a preliminary alternative to

experimental testing. Initial testing is performed to validate the regenerative

braking principle employed, to establish the actual operating limits of the

virtual test rig and for an initial analysis of performance improvement by

utilization of the f-RBS system. From the results, it was inferred that using the

f-RBS concept can have a significant impact in recycling wasteful the braking

energy and provide additional energy to the racecar.

3.2 REGENERATIVE BREAKING IN TRAINS

In 1886, the Sprague Electric Railway & Motor Company, founded

by Frank J. Sprague, introduced two important inventions: a constant-speed,

non-sparking motor with fixed brushes, and regenerative braking, the method

braking that uses the drive motor to return power to the main supply system.

During braking, the traction motor connections are altered to turn them into

electrical generators. The motor fields are connected across the main traction

40

generator (MG) and the motor armatures are connected across the load. The

MG now excites the motor fields. The rolling locomotive or multiple unit

wheels turn the motor armatures, and the motors act as generators, either

sending the generated current through onboard resistors (dynamic braking) or

back into the supply (regenerative braking). Compared to electro-pneumatic

friction brakes, braking with the traction motors can be regulated faster

improving the performance of protection. For a given direction of travel,

current flow through the motor armatures during braking will be opposite to

that during motoring. Therefore, the motor exerts torque in a direction that is

opposite from the rolling direction Braking effort is proportional to the product

of the magnetic strength of the field windings, multiplied by that of the

armature windings. Savings of 17% are claimed for Virgin

Trains Pendolinos. There is also less wear on friction braking components.

It is expected that the Delhi Metro will save over

100,000tonsof CO2 from being emitted per year once its phase II is complete

through the use of regenerative braking. The train is slowed by the climb, and

then leaves down a slope, so kinetic energy is converted to gravitational

potential energy in the station. This is normally found on the deep tunnel

sections of the network and not generally above ground or on the cut and

cover sections of the Metropolitan and District Lines. Electricity generated by

regenerative braking may be fed back into the traction power supply; either

offset against other electrical demand on the network at that instant, used

for head end power loads, or stored in line side storage systems for later use.

41

3.3 EXISTING SYSTEM

In the existing system it uses mechanical breaking and it also

needs break shoes. In the existing system the wear and tear is more. The

existing system consist of brake shoes, which is very costly. The noise

produced is more in this system. In this system break shoes needs to be

frequently changed due to the mechanical friction. In the existing system the

energy during breaking is lost in the form of heat

3.4 PROPOSED SYSTEM

In the proposed system it uses electrical energy. In this system during

the breaking time the electrical energy is produced. In this system the noise is

less. Frequent replacement of brake shoes is not required in this system It is

more advantageous than the existing system, it produces electrical energy

during the breaking time. It is a cost effective system and it is a flexible system

The energy during breaking is converted to electrical energy

42

CHAPTER-4

ANALYSIS AND RESULT

4.1 ELECTRICAL SCHEMATIC DIAGRAM

Fig.4.1.ELECTRICAL SCHEMATIC DIAGRAM

43

4.2 CIRCUIT DISCRIPTION

In our design we use 230V, ¼ HP Capacitor start- run single phase

induction motor as prime mover. Prime mover is directly coupled with an

alternator by using belt and pulley arrangement. 120VA, 12V, 10A, 300 rpm

alternator is used. Output of the alternator is connected to a step-up

transformer. The transformer step up 12V AC into 230 V AC supply and this is

fed into an incandescent lamp.

While we applying the brake, giving DC supply to rotor. The rotor will

produce flux. Due to the kinetic energy, the rotor will slowly rotate and come

to rest. During this time an emf will produce in the stator winding and fed to

the step-up transformer and then fed to the load

The DC supply is provided with 12 V 10Ah deep cycle lead acid battery

and this battery is charging by using rectified output of alternator. Three phase

diode bridge rectifier is used as rectifier.

The relay circuit is used to control the braking system properly. Here we

used a 12 V single pole double throw relay.

In an ordinary system, during braking energy will lost in the form of

heat and noise. If we use this system, we can conserve the energy loss due to

braking.

During braking, the traction motor connections are altered turn the

electrical generators. The motor fields are connected across the main traction

generator(MG) and the motor armatures are connected across the load. The

MG now excites the motor fields. The rolling locomotive or multiple unit

wheels turn the motor armatures, and the motors act as generators, either

sending the generated current through onboard resistors (dynamic braking) or

44

back into the supply (regenerative braking).Compared to electro-pneumatic

friction brakes, braking with the traction motors can be regulated faster

improving the performance of wheel slide protection. For a given direction of

travel, current flow through the motor armatures during braking will be

opposite to that during motoring. Therefore, the motor exerts torque in a

direction that is opposite from the rolling direction.

Braking effort is proportional to the product of the magnetic strength of

the field windings, multiplied by that of the armature windings. Savings of

17% are claimed for Virgin Trains. There is also less wear on friction braking

components. The Delhi Metro saved around 90,000 tons of carbon dioxide

(CO2) from being released into the atmosphere by regenerating112,500

megawatt hours of electricity through the use of regenerative braking systems

between 2004 and2007. It is expected that the Delhi Metro will save

over100,000 tons of CO2 from being emitted per year once its phase II is

complete through the use of regenerative braking. Another form of

regenerative braking is used on some parts of the London Underground, which

is achieved by having small slopes leading up and down from stations.

The train is slowed by the climb, and then leaves down a slope, so

kinetic energy is converted to gravitational potential energy in the station. This

is normally found on the deep tunnel sections of the network and not generally

above ground or on the cut and cover sections of the Metropolitan and District

Lines.

45

4.3 COMPARISON OF DYNAMIC BRAKING AND

REGENERATIVE BRAKING

Dynamic brakes unlike regenerative brakes, dissipate the electric energy

as heat by passing the current through large banks of variable resistors.

Vehicles that use Dynamic brakes ("rheostatic brakes" in the UK), unlike

regenerative brakes, dissipate the electric dynamic brakes

include forklifts, diesel-electricl ocomotives, and streetcars. This heat can be

used to warm the vehicle interior, or dissipated externally by large radiator-like

cowls to house the resistor banks. The main disadvantage of regenerative

brakes when compared with dynamic brakes is the need to closely match the

generated current with the supply characteristics and increased maintenance

cost of the lines. With DC supplies, this requires that the voltage be closely

controlled. The AC power supply and frequency converter pioneer Miro Zoric

and his first AC power electronics have also enabled this to be possible with

AC supplies.

The supply frequency must also be matched (this mainly applies to

locomotives where an AC supply is rectified for DC motors).In areas where

there exists a constant need for power unrelated to moving the vehicle such as

electric train heat or air conditioning, this load requirement can be utilized as a

sink for the recovered energy via modern AC traction systems. This method

has become popular with North American passenger railroads where Head End

Power loads are typically in the area of 500 kW year round. Using HEP loads

in this way has prompted recent electric locomotive designs such as the ALP-

46 andACS-64 to eliminate the use of dynamic brake resistor grids and also

eliminates any need for any external power infrastructure to accommodate

power recovery allowing self-powered vehicles to employ regenerative braking

as well. A small number of steep grade railways have used 3-phase power

supplies and 3-phase induction motors. This results in a near constant speed for

46

all trains as the motors rotate with the supply frequency both when motoring

and braking.

4.4 FEASIBILITY OF TECHNOLOGY AND OPERATIONAL

NECESSITIES

Various types of trains can be equipped with regenerative braking:

electric trains, hybrid diesel locomotives and subway trains The more

frequently a train stops, the more it can benefit from regenerative breaking.

Therefore the technique is especially valuable for commuter trains and

subways, which both stop frequently. Electric railway systems can be either

DC or AC powered. It is much easier to implement regenerative breaking for

AC powered systems. For DC powered systems, there are two main barriers.

Most DC powered systems use relatively low voltages and often the generated

electricity cannot be fed back into the public electricity grid. In very dense

suburban DC powered networks, however, regenerative breaking can be an

effective way to reduce the electricity demand. In all other cases, the

effectiveness of regenerative braking is rather low but may be enhanced by

technological upgrades of vehicles and/or substations. These upgrades are

associated with relatively high investment costs. Railway systems working

with AC power can implement regenerative braking with almost no additional

costs. Also the implementation of regenerative braking in diesel powered

locomotives poses no obstacle. Virtually all locomotives are diesel-electric, so

the capacity to do regenerative braking is available

47

4.5 STATUS OF THE TECHNOLOGY AND ITS FUTURE MARKET

POTENTIAL TOP

Regenerative braking is a mature technology. Within Europe,

there is still a considerable difference between countries in the share of rolling

stock that is equipped with regenerative braking, but the share is relatively high

already. Regenerative breaking is relatively standard in new trains. It is also

used in major new high-speed trains. However, friction brakes are still needed

as backup in the case that the regenerative brakes fail. It is possible to use

regenerative braking on these high speed trains because most cars have their

own electric motors, this is in contrast to trains in which only the locomotive

has electric motors. The fourth generation TGVs in France, which are expected

to be commissioned in 2010, will also be equipped with regenerative brakes, as

will the German ICE 3 trains which are to be commissioned in 2012.

4.6 CONTRIBUTION OF THE TECHNOLOGY TO SOCIAL

DEVOLEPMENT TOP 

Contribution by the use of regenerative breaking to socio-

economic development is expected to be low. The Delhi Metro CDM project

(DMRC, 2007) argues for marginally improved local employment in the

operation and maintenance of the trains, but does not go into details on this.

The effects of regenerative braking on air quality depend mainly on the way

the electricity is produced. In general, the introduction of regenerative braking

on electric trains and subway trains will have no direct effect on the local air

quality. However, lowering the electricity demand will lower the emission of

air pollutants, like NOx, SO2 and particulate matter in power generation, if

power generation is based on fossil fuels. For diesel powered locomotives,

hybridization can have a positive direct effect on air quality, depending on the

usage pattern. Locomotives used solely on a marshalling yard can achieve very

48

high reductions in emissions, due to frequent need for braking. However, the

reduction in local air pollution will be limited when the locomotive is used in

long-haul freight trains.

4.7 ELEMENT SPECIFICATIONS

Our design will provide all of the following:

Single Phase Induction Motor: 230V, ¼ HP Capacitor start- run single

phase induction motor

Belt and pulley arrangement

Alternator: 120VA, 12V, 10A, 300 rpm alternator

Voltage Regulator: Zener diode is used to regulate the output voltage

Rectifier: Three phase bridge rectifier. Diode used IN4007

Battery: 10Ah 12VDC deep cycle lead acid battery for compatibility,

convenience, and cost.

Relay: 12V single pole double throw.

Step-up transformer: 12V to 230V AC single phase transformer

Load: 40W 230V incandescent bulb is connected as load.

4.8 RESULT

We construct the regenerative braking system by using the

induction motor, alternator, rectifier, battery, step-up transformer, relay and

incandescent lamp. We successfully take the energy lost due to braking and

convert to 230 V single phase 50 Hz output supply and it is fed to the load.

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CHAPTER 5

CONCLUSION

In ordinary braking system there is a huge amount of energy wasted

while braking. Generally we uses brake shoe and hydraulic systems are used in

locomotives, so the maintenance cost is high and also those system will create

noises and pollution. In our project we can reduce the wastage of energy

during the braking time. This is simple and cost effective way of braking. It

can perform a fast and controlled braking. The locomotives are normally

designed for gradual braking.If we apply this mechanism in electrical

locomotives, we can obtain very good braking with less maintenance cost and

we gather electricity as byproduct from the system, then the electricity is fed

into the bus.

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