Download International Electrical Engineering Journal (IEEJ) Vol. 6 (2015) No.2, pp. 1771-1779

International Electrical Engineering Journal (IEEJ)
Vol. 6 (2015) No.2, pp. 1771-1779
ISSN 2078-2365
http://www.ieejournal.com/
Simulation Design, Control and Analysis
of Induction Motor based AC Chopper
Cholleti Sriram, Voraganti David, Janardhan Rao
[email protected]

Abstract—To use the induction motor for various applications,
controlling of speed is necessary. By having different speed
control techniques of induction motor, stator voltage control is
the only speed control technique which it can vary the voltage
keeping supply frequency as constant at the input side of the
motor, it can be provided by AC Chopper. By varying the
stator voltage using ON-OFF control PWM technique of AC
chopper, the control of speed of an induction motor is achieved.
This paper proposes a stator voltage speed control technique of
induction motor based AC chopper. This paper also discusses
the simulation design, control and analysis of induction motor
by using electro dynamics equations with the help of
Simulink/MATLAB.
Index Terms— Stator Voltage Control, Induction Motor, AC
Chopper, ON-OFF control, PID Control.
I. INTRODUCTION
Speed control of induction motor can be achieved by
controlling the parameters from both the stator side and the
rotor side. However stator side control is preferred because of
inherent advantages such as better efficiency, better control
strategies, economical method etc. Stator side voltage control
is generally an economical method of speed control [4,7].
Stator side voltage control is achieved by two methods
namely, on-off control method and phase angle control
method [6]. For domestic applications where the power rating
of the motor is not very high, stator voltage control is very
much preferred for speed control as speed variation is not
very large [1,5,7].
In this project, an attempt has been made to design a
complete drive system for the stator voltage control of the
induction motor . The voltage control is possible with the use
of an AC chopper which uses a switch for ON - OFF control .
The modeling and simulation is done in SIMULINK, the
versatile GUI tool available in MATLAB. The various tools
available along with the documentation for guidance have
been found to be very useful . Also an attempt has been made
to achieve the required performance using PID control.
Further, as an extension fuzzy logic control is proposed to be
used to achieve good motor operation even under uncertain
load conditions.
Cholleti Sriram et. al..,
The speed control of induction motor is more important to
achieve maximum torque and efficiency. Induction motors
are the most widely used motors for appliances, industrial
control, and automation; hence, they are often called the
workhorse of the motion industry because they are robust,
reliable, and durable and have variable speed range. When
power is supplied to an induction motor at the recommended
specifications, it runs at its rated speed. However, many
applications need variable speed operations. For example, a
washing machine may use different speeds for each wash
cycle. Historically, mechanical gear systems were used to
obtain variable speed. Recently, electronic power and control
systems have matured to allow these components to be used
for motor control in place of mechanical gears.
These electronics not only control the motors speed, but
can improve the motors dynamic and steady state
characteristics. In addition, electronics can reduce the
systems average power consumption and noise generation of
the motor. So speed control of an induction motor is very
important.
Following discusses about the organization of paper:
Chapter I discusses about the introduction of the paper,
Chapter II discusses about the AC Chopper and its operation
using ON-OFF Control method, Chapter III discusses about
the analysis and design of induction motor using electro
dynamics equations, Chapter IV discusses about the
simulation results with the help of Simulink/MATLAB,
Chapter V discusses about the conclusion regarding the
paper.
II. AC CHOPPER
If a thyristor switch is connected between AC supply and
load, the power flow can be controlled by varying the RMS
value of AC voltage applied to load; and this type of power
circuit is known as an AC voltage controller. AC voltage
controllers (ac line voltage controllers) 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
Simulation Design, Control and Analysis of Induction Motor based AC Chopper
1771
International Electrical Engineering Journal (IEEJ)
Vol. 6 (2015) No.2, pp. 1771-1779
ISSN 2078-2365
http://www.ieejournal.com/
voltage applied to a load circuit is controlled by controlling
the triggering angle of the Thyristors in the ac voltage
controller circuits.
In brief, an ac voltage controller is a type of thyristor
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.
Fig 3 Single phase full wave AC voltage controller circuit
Fig.1 AC voltage controller block diagram
There are two different types of thyristor control used in
practice to control the ac power flow
i.
ii.
ON-OFF control
Phase control
In On-Off control technique thyristors are used as
switches to connect the load circuit to the ac supply (source)
for a few cycles of the input ac supply and then to disconnect
it for few input cycles. The thyristors thus act as a high speed
contactor (or high speed ac switch).
In phase control the thyristors are used as switches to
connect the load circuit to the input ac supply, for a part of
every input cycle. That is the ac supply voltage is chopped
using thyristors during a part of each input cycle. The
thyristor switch is turned on for a part of every half cycle, so
that input supply voltage appears across the load and then
turned off during the remaining part of input half cycle to
disconnect the ac supply from the load. By controlling the
phase angle or the trigger angle „α (delay angle), the output
RMS voltage across the load can be controlled.
The basic principle of on-off control technique is
explained with reference to a single phase full wave ac
voltage controller circuit shown in Fig.2. The thyristor
switches T1 and T 2 are turned on by applying appropriate
gate trigger pulses to connect the input ac supply to the load
for „n‟ number of input cycles during the time interval t ON.
The thyristor switches T 1 and T 2 are turned off by blocking
the gate trigger pulses for „m‟ number of input cycles during
the time interval tOFF. The ac controller ON time t ON usually
consists of an integral number of input cycles.
Cholleti Sriram et. al..,
Fig.4. Waveforms
III. PID CONTROLLER
A proportional–integral controller (PID controller) is a
generic control loop feedback mechanism (controller) widely
used in industrial control systems – a PID is the most
commonly used feedback controller. A PID controller
calculates an "error" value as the difference between a
measured process variable and a desired set point. The
controller attempts to minimize the error by adjusting the
process control inputs. However, for best performance, the
PID parameters used in the calculation must be tuned
according to the nature of the system – while the design is
generic, the parameters depend on the specific system.
Simulation Design, Control and Analysis of Induction Motor based AC Chopper
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International Electrical Engineering Journal (IEEJ)
Vol. 6 (2015) No.2, pp. 1771-1779
ISSN 2078-2365
http://www.ieejournal.com/
The PID controller calculation (algorithm) involves two
separate parameters, and is accordingly sometimes called
three term control:
i.
ii.
iii.
the proportional (P)
the integral (I)
the derivative (D)
The proportional value determines the reaction to the
recent error, the integral value determines the reaction based
on the sum of recent errors, and the derivative value
determines the reaction based on the rate at which the error
has been changing. Heuristically, these values can be
interpreted in terms of time: P depends on the present error, I
on the accumulation of past errors, extension fuzzy logic
control is proposed to be used to achieve good motor
operation even under uncertain load conditions.
A. AC Chopper Sub System
AC chopper is modeled as a switch which is opened or
closed in accordance with the signals from the controller.
This AC chopper consists of a pulse generator, summer,
switch, constant and auto scale blocks. Inputs to the switch
are taken from the summer, sine wave and from the constant
blocks. This constant block acts as a ground to the switch.
The output from the switch is given to the auto scale graph.
The SIMULINK block diagram of the AC chopper and its
library functions are shown in Fig.6.
Fig.6 AC Chopper Subsystem
Fig. 5. Block diagram of a generic PID controller
B. Electrical Sub System
IV. MODELLING OF AC CHOPPER FED
INDUCTION MOTOR
With the recent availability of sophisticated software
packages, Simulink/MATLAB has proved to be an extremely
powerful and economic tool in the analysis and application of
electric drive systems. Simulation helps in the selection of
drive motors, converter design, appropriate control strategies
and performance estimation. It also provides better insight
into the operation, ideal models, and non-idealities of
different drive motors.
The entire drive system is made up of smaller subsystems
for the purpose of ease of block diagram construction and
easier analysis.
The subsystems used in the drive system are
a)
b)
c)
d)
Chopper subsystem
Electrical subsystem
Torque subsystem
Mechanical subsystem
Cholleti Sriram et. al..,
The output of the electrical subsystem is the rotor current.
The electrical subsystem can be modeled from the basic
equation of an induction motor which is given by
(R1+R21)I L + (L1+L21) dIL/dt + Eb sin(ωt – θ ) = Vm Sin ωt
The block diagram of the electrical subsystem and its overall
subsystem is shown in Fig. 7 respectively. The electrical
subsystem takes chopper voltage and speed as the inputs. The
output, however, depends upon parameters such as rotor
EMF Eb, slip S, magnetizing reactance Xm and load
resistance RL.. These are modeled and stored as library
functions for use in the electrical subsystem. Each of these
subsystems is discussed henceforth.
Rotor Back EMF Sub System
The rotor EMF in an induction motor is given by the equation
and is shown in the Fig.8.
E 
V 1XmRL
jXmRL  [( R1  R 2' )  j ( X 1  X 2' )}{RL  jXm ]
Simulation Design, Control and Analysis of Induction Motor based AC Chopper
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International Electrical Engineering Journal (IEEJ)
Vol. 6 (2015) No.2, pp. 1771-1779
ISSN 2078-2365
http://www.ieejournal.com/
D. Mechanical Sub System
The mechanical subsystem is shown in the Fig.10 and the
equation is given by
J
d
 Tg  TL  B
dt
Fig.7 Electrical Subsystem
Fig.10 Mechanical Subsystem
Complete Drive System
Fig.8 Rotor EMF Subsystem
C. Torque Sub System
The complete drive system is shown in Fig 11. The
system has been formed after the integration of all the
subsystems mentioned previously. The entire drive system is
divided into subsystems for ease of analysis and to avoid
complicated block diagrams. Each of these subsystems are
modeled individually and then integrated to form a complete
drive system. These subsystems are modeled based on their
mathematical equations. Each subsystem represents a
mathematical relationship between two quantities.
The Torque subsystem is shown in the Fig.9 and the
equation is given by
Te = KR 2 ' I ²
s
Fig.9 Torque Subsystem
Cholleti Sriram et. al..,
Fig.11 Complete Drive System
Simulation Design, Control and Analysis of Induction Motor based AC Chopper
1774
International Electrical Engineering Journal (IEEJ)
Vol. 6 (2015) No.2, pp. 1771-1779
ISSN 2078-2365
http://www.ieejournal.com/
V. SIMULATION RESULTS
Fig.12 Chopper voltage for 40% duty cycle
Fig.15 Chopper voltage for 40% duty cycle
Fig.13 Chopper voltage for 50% duty cycle
Fig. 16. Speed for T L=40Nm without PI
Fig. 17. Speed for T L=40Nm with PI
Fig.14 Chopper voltage for 60% duty cycle
Cholleti Sriram et. al..,
Simulation Design, Control and Analysis of Induction Motor based AC Chopper
1775
International Electrical Engineering Journal (IEEJ)
Vol. 6 (2015) No.2, pp. 1771-1779
ISSN 2078-2365
http://www.ieejournal.com/
Fig.21. Speed for TL=60Nm without PI
Fig.18. Ripples for TL=40Nm without PI
Fig.19. Ripples for TL=60Nm with PI
Fig.20. Speed for TL=60Nm with PI
Cholleti Sriram et. al..,
Fig.22. Ripples for TL=60Nm with PI
Fig.23. Ripples for TL=60Nm with PI
Simulation Design, Control and Analysis of Induction Motor based AC Chopper
1776
International Electrical Engineering Journal (IEEJ)
Vol. 6 (2015) No.2, pp. 1771-1779
ISSN 2078-2365
http://www.ieejournal.com/
Fig.24. Speed for TL=80Nm without PI
Fig.27. Ripples for TL=80Nm with PI
Fig.25. Speed for TL=80Nm with PI
Fig.28. Speed for T L=100Nm without PI
Fig.26. Ripples for TL=80Nm without PI
Fig.29. Speed for T L=100Nm with PI
Cholleti Sriram et. al..,
Simulation Design, Control and Analysis of Induction Motor based AC Chopper
1777
International Electrical Engineering Journal (IEEJ)
Vol. 6 (2015) No.2, pp. 1771-1779
ISSN 2078-2365
http://www.ieejournal.com/
given in tables no. 1, 2 & 3.
Table 1: Steady State speed with Nref = 1000rpm for
different load torques
Load Torque
Without PI
controller
With PI
controller
40 Nm
983 rpm
1150 rpm
60 Nm
972.3 rpm
1060 rpm
80 Nm
963 rpm
1025 rpm
100 Nm
958 rpm
995.5 rpm
Fig.30. Ripples for TL=100Nm without PI
Table 2: Speed ripple percentage for different load torques
Fig.31. Ripples for TL=100Nm with PI
Comparison for speed ripples with and without PI
controller. Percentage of speed ripple can be calculated by
using formula
Speed ripple % = (Nmax – Nmin) / (Navg)
Load Torque
Without PI
controller
( in %)
With PI
controller
( in %)
40 Nm
0.039
0.013
60 Nm
0.1022
0.023
80 Nm
0.1037
0.041
100 Nm
0.168
0.01704
Table 3: Settling time in speed waveforms for different load
torques with Nref = 1000rpm
Without PI
With PI
controller
controller
Load Torque
( in sec)
( in sec)
40 Nm
2.65
2.1
60 Nm
2.93
1.9
80 Nm
3.23
1.7
100 Nm
4.465
1.55
For a load torque of 40Nm,
Speed ripple % = (1150 – 1149.19) / (1149.56)
= 0.013 %
Summary of observation and analysis of speed ripple for the
proposed ON-OFF control with and without PI controller is
Cholleti Sriram et. al..,
Simulation Design, Control and Analysis of Induction Motor based AC Chopper
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International Electrical Engineering Journal (IEEJ)
Vol. 6 (2015) No.2, pp. 1771-1779
ISSN 2078-2365
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VI. CONCLUSION
In this paper, speed control of AC chopper fed induction
motor is investigated. Phase control strategy can create
problems like poor power factor. Chopping technique is
found to solve the problems associated with the phase control
and hence, in this project, chopping technique is employed to
analyze the speed of induction machines when fed by such a
power converter. An attempt is made to simulate the
complete drive system in SIMULINK software package in
MATLAB platform. PID controller is added for the better
performance of the induction motor and the analysis of the
induction motor is done with the help of graphs. The speed
ripple is also calculated with and without PID controller for
different load torques.
VII. REFERENCES
[1] H.S.Rajamani and R.A.McMahon, “Induction motor
drives for domestic applications,” IEEE Industry
Applications Magazine, Vol.3, No.3, May/June 1997.
[2] D.G.Kokalj, “Variable frequency drives for commercial
laundry machines,” IEEE Industry Applications
Magazine, Vol. 3, No.3, May/June 1997.
[3] V V Sastry, P Sankar Ganesh and V Madhavi, “High
performance induction motor controller using thyristor
voltage feedback”, Proceedings of the IEEE International
conference on Power Electronics, Drives and Energy
systems for Industrial growth, New Delhi, pp.44-47,
January 1996.
[4] Derek A Paice, “Induction motor speed control by stator
voltage control”, IEEE transactions on Power apparatus
and systems, Vol. PAS-87, pp.585-590, February 1968.
[5] Characteristic Performance Analysis of Squirrel Cage
Induction Motor, Xie Ying, Magnetics, IEEE
Transactions on Volume: 45 , Issue: 2 , Part: 1 Digital
Object
Identifier:
10.1109/TMAG.2008.2009934,
Publication Year: 2009 IEEE Journals.
[6] Drive system of single side linear induction motors, Li
Yaohua, Ren Jinqi, Electrical Machines and Systems,
2008. ICEMS 2008. IEEE Conference.
[7] A Novel Technique for optimal efficiency control of
induction motor fed by AC chopper Saracoglu, B, Kale,
M,
Ozdemir,
E Power Electronics Specialists
Conference PESC 04. 2004 IEEE 35th Annual, Vol.5
Cholleti Sriram et. al..,
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