Control of a Three Phase Induction Motor using Single Phase Supply

International Journal of Engineering Trends and Technology- Volume3Issue3- 2012 

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, 

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 90 0 phase shift[2] from a threephase 

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 threephase 

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]. 

Andhra Pradesh, INDIA 

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, V s is an AC voltage at a frequency, f i 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 α P for 

the positive converter and α N 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 V s , 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). 

II. 

CYCLOCONVERTER 

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


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

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

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

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

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 V s , 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. 



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

times less than that of V s , the input voltage, i.e. f o /f i = 1/4. 

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

Cycloconverters that have f o /f i > 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 V 0 can be changed by varying the number of 

cycles the positive and the negative converters work. It can 

only change as integer multiples of f i 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∟0 0 and teaser 

transformer having 220∟90 0 . 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. 



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 0 0 Delay. Second one is converted singlephase 

to single-phase with 90 0 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∟0 0 and teaser 

transformer having 440∟90 0 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 threephase 

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 threephase 

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.

Control of a Three Phase Induction Motor using Single Phase Supply

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