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,
Andhra Pradesh, INDIA
Abstract- In Industrial applications, two forms of electrical
This converter consists of back-to-back connection of two
energy are used: Direct Current (DC) and Alternating Current full-wave rectifier circuits. Fig. 1 shows the operating
(AC). Usually constant voltage, constant frequency Single-Phase waveforms for this converter with a resistive-inductive load.
or Three-Phase AC is readily available. However, for different The input voltage, V is an AC voltage at a frequency, f as
s
i
applications different forms, magnitudes and/or frequencies are
shown in Fig. 1b. For easy understanding assume that all the
required. This paper proposes how the Three-Phase inductive
load is run by a Single-Phase supply by using Cycloconverter and Switches (IGBT) are fired at α=0° firing angle, i.e. Switches
a Scott-T connected Transformer. The controlling of a Three- act like diodes. Note that the firing angles are named as αP for
Phase Induction Motor is done by Frequency variable method. the positive converter and αN for the negative converter.
Consider the operation of the Cycloconverter to get half of
Single-Phase to Three-Phase for motors offered by using high in
performance, low on maintenance and is used to reduce of the input frequency at the output. For the first cycle of Vs, the
breakdown of electrical equipment, our range is also suitable for positive converter operates supplying current to the load. It
saving energy and require low maintenance.
rectifies the input voltage; therefore, the load sees two positive
half cycles as seen in Fig. 1c. In the next cycle, the negative
Keywords- Cycloconverter, Scott-T Transformer, Single-Phase to converter operates supplying current to the load in the reverse
Three-Phase conversion.
direction. Note that when one of the converters operates the
other one is disabled, so that there is no current circulating
I. INTRODUCTION
between the two rectifiers.
A Scott-T Transformer[1] is a type of circuit used to derive
two-phase electric power with 900 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].
Fig.1a. Single Phase Cycloconverter with Sinusoidal Pulse Width Modulation
Frequency changers is an expanding field of power (Converter Consists of Back-to-Back Connection of two full-wave rectifiers).
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
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International Journal of Engineering Trends and Technology- Volume3Issue3- 2012
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 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.
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International Journal of Engineering Trends and Technology- Volume3Issue3- 2012
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:
√
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.
----- (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
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.
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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.
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International Journal of Engineering Trends and Technology- Volume3Issue3- 2012
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 singlephase 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.
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International Journal of Engineering Trends and Technology- Volume3Issue3- 2012
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 ScottT 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).
[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.
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.
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