1 Phase to 3 Phase

International Journal of Engineering Trends and Technology- Volume3Issue3- 2012

ISSN: 2231-5381 http://www.internationaljournalssrg.org Page 431

Control of a Three Phase Induction Motor using

Single Phase Supply

G. R. Sreehitha#1

, A. Krishna Teja*2

, Kondenti. P. Prasad Rao#3

Department of Electrical & Electronics Engineering, K L University,

Andhra Pradesh, INDIA

Abstract- In Industrial applications, two forms of electrical

energy are used: Direct Current (DC) and Alternating Current

(AC). Usually constant voltage, constant frequency Single-Phase

or Three-Phase AC is readily available. However, for different

applications different forms, magnitudes and/or frequencies are

required. This paper proposes how the Three-Phase inductive

load is run by a Single-Phase supply by using Cycloconverter and

a Scott-T connected Transformer. The controlling of a Three-

Phase Induction Motor is done by Frequency variable method.

Single-Phase to Three-Phase for motors offered by using high in

performance, low on maintenance and is used to reduce of

breakdown of electrical equipment, our range is also suitable for

saving energy and require low maintenance.

Keywords- Cycloconverter, Scott-T Transformer, Single-Phase to

Three-Phase conversion.

I. INTRODUCTION

A Scott-T Transformer[1] is a type of circuit used to derive

two-phase electric power with 900 phase shift[2] from a three-

phase source, or vice-versa. The Scott connection evenly

distributes a balanced load between the phases of the source.

The Scott three-phase transformer was invented by a

Westinghouse engineer, C. F. Scott, in the late 1890’s to bypass Thomas Edison’s more expensive rotary converter and

thereby permit two-phase generator plants to drive Nikola

Tesla’s three-phase motors[3].

Two-phase motors draw constant power the same as three-

phase motors, so a balanced two-phase load is converted to a

balanced three-phase load. However if the two-phase load is

not balanced, the Scott-T transformer cannot fix this.

Unbalanced current on the two-phase side causes unbalanced

current on the three-phase side[1].

Frequency changers is an expanding field of power

conversion technology. The increasing utilization of a.c

motors in variable speed drives and the generation of electrical power from variable speed sources are examples of

this field applications[4]. Cycloconverters are suitable for

large a.c. machines because it has advantages: it has high

efficiency owing to the simple construction of the main

circuit, which consists, in its basic form, simply of an array of

IGBT switches[5]. The application of a Cycloconverter is

rather limited, because the control circuit is often very

complex, and therefore expensive[6].

II. CYCLOCONVERTER

This converter consists of back-to-back connection of two

full-wave rectifier circuits. Fig. 1 shows the operating

waveforms for this converter with a resistive-inductive load.

The input voltage, Vs is an AC voltage at a frequency, fi as

shown in Fig. 1b. For easy understanding assume that all the

Switches (IGBT) are fired at α=0° firing angle, i.e. Switches act like diodes. Note that the firing angles are named as αP for

the positive converter and αN for the negative converter.

Consider the operation of the Cycloconverter to get half of

the input frequency at the output. For the first cycle of Vs, the

positive converter operates supplying current to the load. It

rectifies the input voltage; therefore, the load sees two positive

half cycles as seen in Fig. 1c. In the next cycle, the negative

converter operates supplying current to the load in the reverse

direction. Note that when one of the converters operates the

other one is disabled, so that there is no current circulating

between the two rectifiers.

Fig.1a. Single Phase Cycloconverter with Sinusoidal Pulse Width Modulation

(Converter Consists of Back-to-Back Connection of two full-wave rectifiers).

Lenovo

Highlight

Lenovo

Highlight



Fig.1b. Input Voltage to the Cycloconverter having f = 50 Hz Frequency.

Fig.1c. Output Voltage of the Cycloconverter having f/2 = 50/2 Hz Frequency

Fig.1d. Output Voltage of Cycloconverter having f/4 = 50/4 Hz Frequency.

Fig.1. Single Phase Cycloconverter with R-L load.

To get one-fourth of the input frequency at the output, for

the first two cycles of Vs, the positive converter operates

supplying current to the load. It rectifies the input voltage;

therefore, the load sees 4 positive half cycles as seen in Fig.

1d. In the next two cycles, the negative converter operates

supplying current to the load in the reverse direction.

Fig.2a. Positive Gate Pulse for Positive Conversion (for f/2).

Fig.2b. Negative Gate Pulse for Negative Conversion (for f/2).

Fig.2. Control Pulses for Cycloconverter (α=0° firing angle).



The frequency of the output voltage, Vo in Fig. 1d. is 4

times less than that of Vs, the input voltage, i.e. fo/fi = 1/4.

Thus, this is a step-down Cycloconverter. On the other hand,

Cycloconverters that have fo/fi > 1 frequency relation are

called step-up Cycloconverters. Note that step-down

Cycloconverters are more widely used than the step-up ones. The frequency of V0 can be changed by varying the number of

cycles the positive and the negative converters work. It can

only change as integer multiples of fi in 1f-1f Cycloconverters.

With the above operation, the 1f-1f Cycloconverter can only supply a certain voltage at a certain firing angle α. The dc

output of each rectifier is:

√

----- (1)

where V is the input rms voltage.

Then the peak of the fundamental output voltage is

( )

√

----- (2)

Equation 2 implies that the fundamental output voltage

depends on α. For α = 0°, where

√

. If α = (π/3)°, then . Thus varying ,

the fundamental output voltage can be controlled. Constant operation gives a crude output waveform with rich harmonic

content. With different 's, the less are the harmonics.

III. SCOTT – T TRANSFORMER

Assuming the desired voltage is the same on the two and three phase sides, the Scott-T transformer connection consists

of a centre-tapped 1:1 ratio main transformer, T1, and an

86.6% (0.5√3) ratio teaser transformer, T2. The centre-tapped

side of T1 is connected between two of the phases on the

three-phase side. Its centre tap then connects to one end of the

lower turn count side of T2, the other end connects to the

remaining phase. The other side of the transformers then

connect directly to the two pairs of a two-phase four-wire

system.

Fig.3. Scott-T Transformer (2ø to 3ø).

Fig.4. Shows the characteristics of a Three Phase Induction

Motor with the input voltage 220V and frequency 50Hz. The

main transformer of a Scott-T having 220∟00 and teaser

transformer having 220∟900. Fig.4a. shows one of the three

phase voltages at output of the Scott-T transformer. Here input

is always equal to output voltage magnitude, because the transformer ratio is 1:1.

Fig.4a. Scott-T Transformer Circuit in MATLAB – Simulink.


ISSN: 2231-5381 http://www.internationaljournalssrg.org 34

Fig.4b. One of Three Phase voltage Waveform (Output of Scott-T Transformer).

Fig.4c. Electromagnetic Torque waveform with 220V/50Hz Single Phase supply.

Fig.4d. Rotor Speed waveform with 220V/50Hz Single Input supply.

Fig.4e. Stator Three Phase Current waveform with 220V/50Hz Single Phase supply.

Fig.4. Performance of Three Phase Induction Motor with 220V/50Hz Single Phase Input supply.



IV. 1-ø TO 3-ø CONVERSION WITH

CYCLOCONVERTER & SCOTT-T TRANSFORMER

This paper proposed a circuit for industries to run three

phase induction loads with single-phase supply. This is done

by MATLAB Simulink.

At very first, single-phase supply converted to two-phase

supply through two single-phase Cycloconverters. In these

two Cycloconverters, one is directly converted single-phase to

single-phase with 00 Delay. Second one is converted single-phase to single-phase with 900 Delay. These two supplies

called as two-phase supply. This two-phase supply directly

fed to the Scott-T transformer. Here this transformer converts

two-phase to three-phase to drive the three-phase induction

load.

In the second section the Cycloconverter operation

explained with sinusoidal pulse width modulation technique

(SPWM). But in this section Cycloconverter operated with

manual pulse generator. Because, the output of a

Cycloconverter having more dc component by using SPWM

technique. To mitigate the dc component with LC-filter. We

are not got the filter values exactly.

Fig.5a. Cycloconverter & Scott-T Transformer Circuit to drive Three-Phase Inductive Loads in MATLAB – Simulink.

Fig.5b. Electromagnetic Torque waveform.



Fig.5c. Rotor Speed waveform.

Fig.5d. Stator Three Phase Current waveform.

Fig.5. Performance of Three Phase Induction Motor (i.e., With Two Single-Phase Cycloconverters & one Scott-T Transformer).

Fig.5. Shows the characteristics of a Three Phase Induction

Motor with the input voltage 220V and frequency 50Hz. The

main transformer of a Scott-T having 440∟00 and teaser

transformer having 440∟900 as input voltage. These two

voltages got by the two single-phase Cycloconverters. Fig.5b.

shows the Electromagnetic magnetic torque. Fig.5c. shows the

rotor speed. Fig.5d. shows the three-phase stator current. Here

input is always equal to output voltage magnitude of the Scott-

T transformer, because the transformer ratio is 1:1.

The main advantage of this is, to get variable speed by

varying the frequency at the input side. This is type of

mechanism is very easy and simple compare to other control techniques (i.e., controlling of three-phase supply directly).

V. CONCLUSION

This paper proposes a new topology for controlling a three-

phase induction motor with single-phase supply. Here to

control of Cycloconverter by the firing pulses. With the help

of variable frequencies got the variable speeds of a three-

phase induction motor. The major role of a Scott-T

transformer is used to convert two-phase, output of two

Cycloconverters to three-phase.

ACKNOWLEDGMENT

It is our sincere obligation to thank our well-wishers Dr. M.

Venu GopalaRao,Ph.D. EEE HOD, Mr. D. Seshi Reddy,M.Tech.

(Ph.D.), Associate Professor & Mrs. S.V.N.L. Lalitha,M.Tech.

(Ph.D.), Associate Professor in KL University at Vaddeswaram,

Guntur Dist.

REFERENCES

[1] Mazin, Hooman Erfanian; Gallant, Joey (August 14, 2009, 2010). "A

Probabilistic Analysis on the Harmonic Cancellation Characteristics of

the Scott Transformer". J. Electromagnetic Analysis & Applications 2:

18–24. Retrieved 20 December 2011.

[2] Distribution Transformer Manual, GET-2485T. Hickory, NC: General

Electric Company. 1996. pp. 64.

[3] Harold C. Passer, The Electrical Manufacturers, 1875-1900, Harvard,

1953, p. 315.

[4] Rezgar Mohammed Khalil, Maamoon Al-Kababjie, ”Modeling and

Simulation of multi-pulse Cycloconverter fed AC Induction motor and

study of output power factor”, Al-Rafidain Engineering, vol.15, no.1,

2007.

[5] Miyazawa, S. Nakamura, F. and Yamada, N. “Effective Approximation

Suitable for the Control Algorithm of Microprocessor Based

Cycloconverter”, IEEE Transaction, August 1988.

[6] Mohammed, B.A., “Microprocessor Based Control of Cycloconverters”,

M.Sc. Thesis, University of Mosul, Iraq, December 1990.

http://www.scirp.org/fileOperation/downLoad.aspx?path=JEMAA20100100003_75647348.pdf&type=journal



Lenovo

Highlight

1 Phase to 3 Phase

Documents

Transcript of 1 Phase to 3 Phase