Converting Single Phase Electric Signal to 3phase Using Voltage Doubler and Inversion Technique by...

7/27/2019 Converting Single Phase Electric Signal to 3phase Using Voltage Doubler and Inversion Technique by Daniel Ikhalo

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ABSTRACT

Most residential homes do not have access to

three-phase electric power at a reasonable price.

Hence operating three-phase machines and equipment

at homes and small scale industries becomes invariably

impossible. A possible solution is to contrive a way to

use the single-phase to three-phase converter that

converts single-phase 220 – 240Vac electric power into

three phase 380 – 430Vac electric power. It involves

the use of a micro controller, solid state half bridge

switches etc. the output is a three-phase line voltage of

380-430V and a rating of 800KVA – 3200KVA.

1.0 INTORDUCTION

The major portion of all electrical power

uses balanced 3 phase systems. Power flow in single

phase circuits is pulsating; Single-phase power is not

smoothly delivered. The sine wave of our voltage

goes from V+ to zero to V- to zero, and back to V+

fifty times a second. In this case the power (P)

delivered equals the voltage (V) times the current (I)

or P=VxI. Each time the voltage goes to zero the

power goes to zero. So single-phase delivers a torque

to the shaft of a motor that pulses from full power to

zero - 100 times a second, with small motors [1].

Three-phase power uses three sine waves that are

separated by 1200. When any one sine wave is at zero

the other two are still delivering power to the motor

shaft. In fact, the SUM of the power delivered by the

three waves is perfectly CONSTANT, so power to

the motor shaft is constant and smooth. On big

motors this helps keep vibration down and makes the

bearings last longer. This smoothness or constant

torque also applies to power generators [1].

To electricity consumers, that consistency in power

delivery is the major benefit. The design of three-

DESIGN AND CONSTRUCTION OF A SINGLE PHASE TO

THREE PHASE SUPPLY LINE CONVERTER

Daniel Ikhalo, B.Eng/E.E.E

Covenant University, Km 10, Idiroko Road, Canaan-Land. Ota.Phone No: +234(0)8131631137 Email: [email protected]

Dr Francis E. Idachaba, Ph.D/E.E.E

Covenant University, Km 10, Idiroko Road, Canaan-Land. Ota.

Phone No: +234(0)8039570321 Email: [email protected], [email protected]

mailto:[email protected]










phase motors, with one set of windings for each

phase, is highly efficient and allows three-phase

motors to draw significantly less current than the

equivalent single-phase motor [1].

Small industries often face the problem of three-

phase equipment with no three-phase service.

Fortunately, there are several ways to make that

equipment - often large, valuable and quite useful

equipment become operational [1].

1.4 METHODOLOGY

220-240V single-phase AC power is fed into

the single-phase to three-phase converter the supplied

voltage is rectified to DC to power the PIC 16F876A

micro-controller, the driver circuitry and also the half

bridge circuitry.

The PIC 16F876A micro-controller is programmed to

generate 3 out of phase logic signals separated by

1200.

The Driver circuitry using TLP250 I.C amplifies

logic signal from the micro-controller to drive

MOSFET switches to prevent micro-controller from

burning.

The Half bridge circuitry made of a number of

MOSFETs used for switching the signals at various

phases thereby inverting the signal which is now 3-

phase sinusoidal signal.

In summary, it involves the design and construction

of:

A power supply circuit that rectifies AC

power to DC power

A micro controller that produces logic

signals

A driver stage that amplifies logic signals

and a half bridge circuit from which the

thee-phase output is produced.

3.2 BLOCK DIAGRAM

3.3 DESIGN SPECIFICATION:

Input voltage = 200-240V single-phase A.C

Frequency = 50Hz

Figure 1: The Block Diagram



Output voltage = 380-430V line voltage

Rating = 800KVA – 3200KVA

3.5 THE POWER SUPPLY STAGE:

First, the ac encounters a transformer that steps the

voltage either down or up, depending on the needs of

the electronic circuit. For the purpose of this project,

to power the PIC

16F877A

and the driver circuit 5V

and 12V are needed respectively, First the

transformer steps down the voltage from 220-240Vac

to 12Vac, Second, the ac is rectified so that it

becomes pulsating dc with a frequency of 50Hz. This

is almost always done with one or more

semiconductor diodes. For this project, a bridge

rectifier is used. Third, the pulsating dc is filtered, or

smoothed, out so that it becomes a continuous

voltage having either positive or negative polarity (or

both) with respect to ground. Finally, the dc voltage

might need to be regulated. Some equipments can put

up with some voltage changes.

Power supplies that provide more than a few volts

must have features that protect the user from

receiving a dangerous electrical shock. All power

supplies need fuses and/or circuit breakers to

minimize the fire hazard in case the equipment shorts

out. For this project, no fuse/circuit breaker is

necessary because the dc output is only 12V.

To power the IRFIBC30G Mosfet switches this IC’s

require 380-430Vdc to operate efficiently, here the

220-240Vac is stepped down to 200Vac, Second the

ac is rectified and with the aid of two capacitors the

voltage is doubled to 2Vmax.

The voltage doubler circuit used in this project

converts 200Vrms to dc, to power the Mosfet

switches with a voltage of 566Vdc. Since a high

voltage dc is required large values of capacitors are

chosen for the task 1800µF, 400V. The PIV of the

diode is 1000V also because of the high dc voltage.

Transformer voltage rating = 220/200V.

Vmax across both capacitors = √ 2 * Vrms = 200√ 2.

And the voltage at the output of the voltage multiplier

= 2Vmax = 2 * (200√ 2) = 400√ 2

This is an approximate of 566Vdc.

Figure 2: Power Supply block diagram

Figure 3: Block diagram of a voltage doubler power supply



3.6 THE PIC 16F876A MICRO-CONTROLLER:

The purpose of this chip in this project is to generate

3 out of phase logic signals to switch the Mosfets at a

time interval of 3.33ms. Figure 20shows the

arrangement of the chip in the circuit diagram.

5Vdc is supplied to the chip through a high resistance

(4.7KΩ) to limit the current entering into the chip.

The crystal oscillator is an electronic oscillator circuit

that uses the mechanical resonance of a vibrating

crystal of piezoelectric material to create an electrical

signal with a very precise frequency. The frequency

generated is converted to time and sent to the PIC

chip to maintain stable clock signal to the micro-

controller. It is connected with two capacitors each

22pF to ground.

The outputs S1-S6 are connected to 6 TLP250

integrated circuits (Mosfet drivers) supplying logic

signals of 1’s and 0’s to switch ON or OFF the power

Mosfets as shown in the sequence table below. The

light emitting diode is connected through a 1KΩ

current limiting resistor to indicate if there is power

supplied to the chip.

3.6.1 THE MICRO-CONTROLLER

FLOWCHART:

The main function of the micro controller is to

generate signals to switch Mosfets ON and OFF at

different time intervals.

The Mosfets can be arranged in form of a H-Bridge,

representing each Mosfet with alphabets A-F.

Figure 4: PIC16F876A Chip in the circuit diagram

Figure 5: The Micro-controller Flowchart

Figure 6: The H-bridge Mosfet arrangement

sequence that the micro-controller works with

http://en.wikipedia.org/wiki/Electronic_oscillator

http://en.wikipedia.org/wiki/Resonance

http://en.wikipedia.org/wiki/Crystal

http://en.wikipedia.org/wiki/Piezoelectricity#Materials

http://en.wikipedia.org/wiki/Frequency

http://en.wikipedia.org/wiki/Clock_signal

http://en.wikipedia.org/wiki/Clock_signal

http://en.wikipedia.org/wiki/Frequency

http://en.wikipedia.org/wiki/Piezoelectricity#Materials

http://en.wikipedia.org/wiki/Crystal

http://en.wikipedia.org/wiki/Resonance

http://en.wikipedia.org/wiki/Electronic_oscillator



STEPS TAKEN BY PIC MICRO

CONTROLLER

1.

Start

2.

Initialize

3. Drive A and D

4. Wait 3.3ms

5. Turn off A and D

6. Drive A and F

7.

Wait 3.3ms

8.

Turn off A and F

9.

Drive C and F

10. Wait 3.3ms

11. Turn off C and F

12. Drive C and B

13. Wait 3.3ms

14. Turn off C and B

15.

Drive E and B

16.

Wait 3.3ms

17. Turn off E and B

18. Drive E and D

19. Wait 3.3ms

20. Turn off E and D

21. Goto 3.

The sequence table

A 1 1 0 0 0 0

B 0 0 0 1 1 0

C 0 0 1 1 0 0

D 1 0 0 0 0 1

E 0 0 0 0 1 1

F 0 1 1 0 0 0

The sequence is continuous that is why there is no

end in the flowchart.

3.33ms is delayed on each time interval, the total

period for the six Mosfets is:

3.33ms * 6 = 20ms; frequency = 1/T = 1/(20*10-3) =

50Hz this is the frequency of the output signal.

3.7 THE TLP250 INTEGRATED CIRCUIT (IC):

Used to drive the gate of the Mosfet, the signal

produced from the micro-controller is not sufficient

to power the switches. The IC is supplied with 5v

signal from microcontroller, this 5V signal is not

sufficient to perform the switching operation in the

Mosfet and the TLP250 chip is supplied with 12V

from the power supply and this is what is used to

drive the power Mosfets. Two TLP250 IC’s are

used to drive two Mosfets respectively (high end and

Table 1: The micro-controller command sequence table



low end) to produce a phase. The high end Mosfet is

connected to the 380-430Vdc supply while the low

end Mosfet is connected to the ground 0V. The

maximum input current rating of the chip is 10mA,

the input voltage from the micro-controller is 5V

therefore, from V = I * R; R = V / I; R = 5 / 10*10 -3 =

500Ω, but the maximum current should not be

allowed. A 1KΩ resistor was chosen to allow about

5mA into the chip, which is 50% of its maximum

capacity.

3.8 THE IRFIBC3OG MOSFET SWITCHES

This is an N-channel Mosfet, the N-channel,

Enhancement-mode MOSFET operates using a

positive input voltage and has an extremely high

input resistance (almost infinite) making it possible to

interface with nearly any logic gate or driver capable

of producing a positive output [2]. Also, due to this

very high input (Gate) resistance we can parallel

together many different MOSFETs until we achieve

the current handling limit required. While connecting

together various MOSFETs may enable us to switch

high currents or high voltage loads [2].

The operation of the enhancement-mode MOSFET

can best be described using its I-V characteristics

curves shown below. When the input voltage, (VIN )

to the gate of the transistor is zero, the MOSFET

conducts virtually no current and the output voltage,

( VOUT ) is equal to the supply voltage VDD. So the

MOSET is "fully-OFF" and in its "cut-off" region.

The minimum ON-state gate voltage required to

ensure that the MOSFET remains fully-ON when

carrying the selected drain current can be determined

from the V-I transfer curves above [2].

In the saturation or linear region, the transistor will

be biased so that the maximum amount of gate

voltage is applied to the device which results in the

channel resistance R DS(on) being as small as possible

with maximum drain current flowing through the

MOSFET switch. Therefore the MOSFET is

switched "Fully-ON" [2].

Figure 7: I/V characteristics of a Mosfet indicating

the saturation and cut-off regions where it acts as a

switch in its ON and OFF state respectively



3.8.1 PRINCIPLE OF OPERATION OF

MOSFET

The principle of operation of this Mosfet in this

circuit is switching the three 1200 out of phase logic

dc signals sent to it to ac signals. This can be done by

rearranging the six Mosfets in the form of a h-bridge

and thus having the high end Mosfets connected to

the supply line and low end Mosfets connected to

ground as shown in the figure below.

The Mosfet switches are supplied with 566V dc from

the voltage doubler circuit because the VDS (drain-

source) breakdown voltage is 1000V. If the system

were to be used to drive an inductive load, like an AC

motor, there is an effect called the flyback or back

emf or rather spikes. If these are not suppressed, they

could create a high voltage spike at the output of the

switches, high enough to break them down. Those

RC networks are called snubbers and are meant to

suppress the magnitude of such spikes. In this circuit

an RC circuit of resistance 100KΩ and capacitance

100µF in series is connected to the output of each

mosfetto suppress these spikes at the output of the

Mosfet.

3.9 THE POWER OUTPUT:

The output rating of this device is 0.8KVA - 3.2KVA

that is because the current rating (pulsed source

current rating) of the IRFIBC3OG Mosfet is 10A and

it is not advisable to use the full current rating of the

device. This Mosfet was chosen because it has a

voltage rating of 1000V (drain to source breakdown

voltage). The output voltage range is 380-430V. And

can be used for purely resistive 3 phase loads like

industrial heaters that consume from 760W-3KW

because the power factor is unity. If the load is an AC

motor the power factor will be considered and is

between 0.8-0.9 and therefore the power consumed

between 600W and 2.4KW.

Figure 8: The Six IRFIBC30G Mosfets connected

in the form of a h-bridge



4.2 IMPLEMENTATION:

After the bottom-up approach of testing had been

carried out and all errors debugged, the actual

implementation could be done. An empty white

casing was used for this project. After purchasing the

transformers, they were carefully screwed to the

bottom of the casing along with the two 1800µF

capacitors used in the voltage doubler circuit. The

power supply, PIC micro-controller, TLP250 IC,

Mosfet switches were soldered on a printed circuit

board and fixed with the wires connected

appropriately. An LED is connected from the output

of the microcontroller to indicate that there is single

phase power supplied to the circuit. The output and

input terminals were connected to the top of the

casing for easy measurement.

4.3 TESTING

In testing a system, the bottom-up approach or the

top-down approach can be used. The former involves

testing the different stages of the system separately

until the whole system has been tested, therefore

showing functionality. This is advantageous in that

errors that might occur in certain stages can be

detected early and corrected. This process involves

testing the functionality of the system entirely before

testing the stages. This project shall make use of the

bottom-up approach in testing.

4.3.1 TESTING THE POWER SUPPLY

The circuit for the power supply was initially

connected on a bread board and testing using a light

emitting diode to check if current was flowing in the

circuit. The power supply is designed to supply 12V

and 5V to the PIC microcontroller and IC

respectively. It was also tested with a multimeter.

Figure 9: Soldered components on top of the

Printed Circuit Board (PCB)

Figure 10: Testing the Power supply connected

on a bread board



4.3.2 TESTING THE SWITCHING SEQUENCE

OF THE IRFIBCO3G MOSFETS

Waveform A and B are always 180 degree out of

phase, whenever A is high, B is low and when B is

high A is low. Same goes for the pair C-D and E-F.

The phase difference however between A and C is

120 degree. You can depict that by realizing that each

waveform is actually high for 1/3 of the whole duty

cycle, so 1/3 of 360 degree is 120. When A is making

a negative transition (from 1 to 0) at phase angle 120

degree, this is the same point at which C is making a

positive transition (0 to 1) which A has made 120

degree ago.

4.3.3 TESTING THE RMS OUTPUT VOLTAGE

WITH A MULTIMETER

The pictures above show a multimeter measuring the

output voltage from the converter. The voltage being

measured is the rms voltage, and the peak voltage can

Figure 11: waveforms produced by PIC for

switching operation of the Mosfets on Proteus

software

Figure 12: Testing the Power output: line voltage

between two lines 422V

Figure 13: Testing the Power output: line voltage

between two lines 400V



be gotten by multiplying this rms value by the root of

two. i.e. Vpeak = √ 2Vrms.

4.3.4 TESTING THE OUTPUT VOLTAGE

WITH AN OSCILOSCOPE

Since the oscilloscope used is two channels, the

figure above shows 2 out of phase signals from two

phases, the Mosfet switching operation cannot

produce a pure sine wave. Resistors 100K and 1K

were connected in series acting as a voltage divider,

with the oscilloscope connected across the 1K

resistor to measure a voltage of about 4.11V so as not

to damage the oscilloscope and ensuring that the

voltage can show within the scale. (1/101)*415 =

4.11V. as shown in the figure below.

5.1 SUMMARY:

This study has succeeded in investigating the design

and construction of a single-phase to three phase

converter. An introduction to the research topic with

the implications of carrying out the study has been

clearly stated in the first chapter; in addition the aims

and objectives, and the methods used in achieving the

desired result have also been indicated. Chapter two

has dealt with the previous works pertaining to this

study as well as discussions about the types of phase

converters and their development. An in-depth

explanation of the design and analysis of a single-

phase to three-phase converter has been duly covered

in chapter three while chapter four has presented the

testing and implementation aspect of the project.

Figure 14: Two out of phase signals from a two

channel oscillosco e

Figure 15: Oscilloscope connected across two

resistors in series acting as a voltage divider



5.2 ACHIEVEMENTS:

The achievements of this project include the

successful conversion of a single-phase power supply

to a three-phase electric power supply, and the

incorporation of solid state electronics and a

microcontroller in accomplishing 3 (1200) out of

phase lines.

5.3 RECOMMENDATIONS:

An LCD (Liquid Crystal Display) can be

incorporated into this project to make it

easier to read the single-phase voltage as

well as the three-phase voltage it is

converted to.

The packaging of the single-phase to three-

phase converter can also be improved upon

to enable easy connection to large size loads.

More research should be conducted into how

this single-phase to three-phase converter

can be run to run multiple loads

simultaneously.

Single-phase to three-phase converters that

make use of solid state electronic

components generally do not have a long

life. Research should also be made about

how they can be made to last longer because

if properly harnessed they can provide

balanced three-phase voltage to three-phase

loads at a very high frequency.

REFERENCES:

[1] Mohamed E. El-Hawary “Electrical

Energy Systems”, 1st edition, 2006, pp

261-262.

[2] Using the power MOSFET as a switch –

MOSFET switching, www.electronics-

tutorials.ws/transistor/tran_7.html , Feb 10,

2011

Converting Single Phase Electric Signal to 3phase Using Voltage Doubler and Inversion Technique by...

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