The role of AC Voltage Regulator in speed control of three phase Induction Motor is to vary the supply voltage which in turn, changes the speed of motor .

1. SPEED CONTROL OF THREE PHASE
INDUCTION MOTOR USING AC VOTAGE
REGULATOR
GUIDED BY:
MR. SONU KUMAR
(Assistant professor)
PRESENTED BY:
SHIVANGEE
KAMINI SINGH
KUMARI PRIYANKA

2.  Introduction
Induction Motor
Three Phase Induction Motor
Speed Control Method
AC Voltage Regulator
 Advantages
 Applications

3.  Speed of induction motor can be controlled by
using three phase AC voltage controller.
 AC voltage controller is a circuit used to convert
fixed ac to variable ac without changing the
frequency.
 This conversion can be made with the use of
power electronic devices such as SCR, IGBT,
MOSFET, etc. is made very efficiently and
flexibly.

4. The implementation of any converter circuit needs
to be tested before going for hardware. This reduces
cost, man power, time. This is achieved by using
simulation software’s were the same model or
topology can be tested with the real time hardware
ratings and device specifications. One such software
for testing power electronic converter circuit is
MATLAB . The applications of this software are
really prove their worth through their real time
applications.

5.  Three-phase induction motors are the most
common and frequently encountered machine
in the industry.
 An induction motor works on transforming
action. The stator works as the primary, while
the rotor works as the secondary. It is also
called asynchronous motor.
 It is simple in design,rugged,low-price and has
easy maintenance.

6.  Three phase induction motors are most widely
used for industrial applications mainly because
they do not require a starting device. Hence it is
self starting.
 Run at approximately constant speed from no
load to full load and speed is less than
synchronous speed.
 The operating principle of three phase induction
motor is based on rotating magnetic field.

7.  It has mainly two parts:
1. Stator-It is the stationary part of the motor.
2. Rotor-It is the rotating part of the motor.
The rotor is separated from the stator by a small
air gap.

8.  An induction motor is practically a constant
speed motor, that means, for the entire loading
range, change in speed of the motor is quite
small.
 Asynchronous motor do not inherently have
the capability of variable speed operation.
 Being widely used, their speed control may
be required in many applications.

9. Speed control of three phase induction motor can be
varied by varying the slip ‘S’ or number of poles ‘p’ or
frequency ‘f’ of the supply.
 The ability of varying any one of the above three
quantities will provide methods of speed control of an
induction The speed motor
= Synchronous speed, in revolutions per minute,
f = AC power frequency
p= Number of poles per phase winding.

10. The speed control of three phase
induction motor are classified as :
1.Supply voltage control.
2.Variable frequency control.
3.Rotor resistance control.
4.Constant V/f control.

11.  AC voltage controller are employed to vary
the RMS value of the alternating voltage
applied to a load circuit by introducing
thyristors between the load and a constant
voltage ac source.
 The RMS value of alternating voltage applied
to a load circuit is controlled by controlling
the triggering angle of the thyristors in the ac
voltage controller circuits.

12. An AC voltage controller is a type of thyristors
power converter which is used to convert a fixed
voltage, fixed frequency ac input supply to obtain
a variable voltage ac output. The RMS value of the
ac output voltage and the ac power flow to the
load is controlled by varying (adjusting) the trigger
angle ‘α’.

13. The three phase loads are connected in star or
delta.
Resistance connected in all three phases are
equal.
Two thyristors connected back to back are
used per phase, thus needing a total of six
thyristors .

14. The current flow is bidirectional, with the current
in one direction in positive half, and other in negative
half.
The thyristors are fired in sequence after a delay
from the natural commutation time.
To turn the thyristors ON, the anode voltage must be
higher than the cathode voltage, and also , a triggering
signal must be applied at its gate.
The turning OFF of a thyristors occurs , if its current
falls to zero.

15.  Lighting/illumination control in ac power
circuit.
 Induction heating.
 Speed control of induction motor.
 Over voltage protection.

16.  Due to natural commutation there is no need
of extra commutation circuitry.
The circuits for AC voltage controller are very
simple.
Low cost & less mentainance.

17. The objective of this minor project is to analyse
and control the speed of three phase Induction
Motor.
Simulink model of three phase Induction Motor
and AC Voltage Regulator is shown in figure1.

18. Fig 1: Simulink model

19. AC Voltage Source: This
block implements an AC
voltage source.
IGBT (Insulated Gate
Bipolar Transistor): The
IGBT block implements a
semiconductor device
controllable by the gate
signal.
Pulse Generator: This
block generates square wave
pulses at regular interval.

20. Three Phase VI Measurement: This block is used to measure
instantaneous three phase voltages and currents in a circuit.
Voltage measurement: This block measures the instantaneous
voltage between two electric modes.
Bus Selector: This block outputs a specified subset of the
elements of the bus at its input.

21. Three Phase Induction machine: The mode of operation
depends upon the sign of the mechanical torque (Tm):
•If Tm is positive, the machine acts as a motor.
•If Tm is negative, the machine acts as a generator.
Terminator: This block is used to cap blocks whose output ports
do not connect to other blocks.

22. Powergui: This block provides useful graphical user interface
(GUI) tools for the analysis of power system blockset models.
Fourier Block: This block performs a Fourier analysis of the
input signal over a running window of one cycle of the
fundamental frequency of the signal.
Scope: This block displays time domain signals with respect to
simulation time.

23. Gain: This block generates its output by multiplying its input by
a specified gain factor.
Display: This block shows the value of input.
Ground Block: This block implements a connection to the
ground.

24. Fig 1.1: input voltage and current waveform of three phase Induction Motor
Results:

25. Fig 1.2: Waveform of stator and rotor current of
three phase Induction Motor

26. Fig 1.3: Output waveform of Electromagnetic Torque

27. Fig 1.4: Speed of three phase Induction Motor

28. From this work and result analysis, it is observed
that speed of a three phase Induction motor can be
efficiently controlled by using AC Voltage Regulator.
 The role of AC Voltage Regulator in speed control
of three phase Induction Motor is to vary the supply
voltage which in turn, changes the speed of motor .
In the present work , the simulation of speed
control of motor at different voltages by using AC
Voltage Regulator is simulated and waveforms are
discussed.

29. 1. Power Electronics (Dr. P.S. Bimbhra)
2. Electrical Machinery (Dr. P.S. Bimbhra)
3. Electric Machines (Ashfaq Husain)
4. Power Electronics (M.H. Rashid)
5. www.electrical4u.com/speed-control-of-three-
phase-induction-motor/
6. http://www.mathworks.com