International Journal of Emerging Technology and Advanced Engineering
Website: www.ijetae.com (ISSN 2250-2459, ISO 9001:2008 Certified Journal, Volume 4, Issue 7, July 2014)
Minimization of Power Loss in SRIM with Rotor Chopper
Control
Dr. K. B. Porate1, Neha R. Kochar2
Electrical Engineering Department, Priyadarshini College of Engineering, RTMNU, Nagpur, Maharashtra, India
Such circuits are widely used in industrial applications
where the drive operation is intermittent such as hoists,
cranes, conveyors, lifts, excavators and high starting toque
are more important with low starting current to avoid
voltage dip.[11]
The torque depends on motor resistance. Therefore,
increasing the rotor resistance at a constant torque causes a
proportionate increase in the motor slip with decrease in
rotor speed. Thus, the speed for a given load torque may be
varied by varying the rotor resistance. The function of this
resistance is to introduce voltage at rotor frequency, which
opposes the voltage induced in rotor winding. [3]
Conventionally, the rotor resistance is controlled
manually and in discrete steps. The main demerit of this
method of control is that energy is dissipated in rotor
circuit resistance, internal and external, and this energy is
wasted in the form of heat. Because of the waste-fullness of
this method, it is used where speed change are needed for
short duration only. [2]
This paper deals with eliminating the drawbacks of a
conventional scheme by using a 3 phase un-controlled
bridge rectifier and a chopper controlled external
resistance. However, this arrangement for controlling the
average value of rotor current (external resistance)
introduces the additional problems of discontinuity in the
rotor winding currents and voltage spikes across the
chopper thyristor. These problems could be taken care of
by having a filter in the rotor circuit. [1]
Abstract— Slip Ring Induction motors are widely used for
high torque and variable speed applications. Conventional
methods of speed control of Slip Induction Motor from rotor
side, lead to wastage of energy, in external resistance. With
the advent of power electronic devices power loss at rotor side
could be minimized and smooth speed control can be
achieved. This paper deals with reducing energy losses by
implementing rotor chopper control, Chopper control along
with filter in open loop and then the system is studied in
closed loop system. A thorough analysis of the steady state
performance of the system is presented for the conventional
vis-à-vis chopper control system. Simulations are made in
MATLAB environment.
Keywords— Slip Ring Induction Motor (SRIM), Chopper
Control, Power Loss, Voltage Spikes.
I. INTRODUCTION
Induction motors are the most widely used electrical
motors due to their reliability, low cost and robustness.
However, induction motors do not inherently have the
capability of variable speed operation. Due to this reason,
DC motors were applied in most of the electrical drives.
But the recent developments in speed control methods of
the induction motor have led to their large scale use in
almost all electrical drives. [1]
Induction motors are a constant speed machines which
account for 90% of the electrical drives used in Industry.
Induction motors are usually constructed to work with a
small value of slip, normally less than 5% at full load.
Therefore the deviation of the motor speed from the
synchronous speed is practically very small. However,
there are certain applications that require enormous
variation of the motor speed [5]. With the increase in
availability of high current power electronic devices,
smooth and quick variation of external resistance
introduced in the rotor circuit of slip ring induction motor
to control its speed, can be accomplished electronically.
Schemes employing chopper control resistance can be used
to obtain a constant torque, constant speed or any desired
characteristics by using a proper feedback circuit along
with it.
II. CONVENTIONAL METHOD [1]
CONVENTIONALLY, the rotor resistance is controlled
manually and in discrete steps. The torque is proportional
to product of rotor current and fundamental magnetic flux
cutting rotor.
The maximum torque is independent of rotor resistance,
but the value of slip at which maximum torque occurs is
directly proportional to the added rotor resistance. Increase
in the rotor resistance does not affect the value of
maximum torque but increases the slip.
180
International Journal of Emerging Technology and Advanced Engineering
Website: www.ijetae.com (ISSN 2250-2459, ISO 9001:2008 Certified Journal, Volume 4, Issue 7, July 2014)
A chopper is a power switch electronically monitored by
a control circuit. When the chopper is in the ON mode all
the time, the equivalent resistance Req in the rotor circuit is
R1. When the chopper is in the OFF mode all the time, the
equivalent external resistance Req in the rotor circuit is (R1
+ R2). If the chopper is periodically regulated so that, in
each chopper period, it is ON for some time and OFF for
the rest, it is possible to obtain a variation of Req between
R1 and (R1 + R2). Thus the chopper electronically alters the
external resistance R2 in a continuous and contactless
manner. The duty cycle ton/(ton + toff) of the chopper is
controlled by a pulse width modulation (PWM) circuit. The
pulse width and, hence, the duty cycle of the chopper is
proportional to ei, the input voltage to the PWM circuit.
FIG. 1 BASIC CONVENTIONAL SCHEME [1]
When high starting torque is needed, the R2 can be
chosen to obtain Tmax at stand still.
FIG. 3 BASIC CHOPPER CIRCUIT [1]
This simple arrangement for controlling the average
value of rotor current (external resistance) introduces the
additional problems of discontinuity in the rotor winding
currents and voltage spikes across the chopper thyristor.
These problems could be taken care of by having either a
first- or second-order filter in the rotor circuit. [4]
FIG. 2 SPEED TORQUE CHARACTERISTICS FOR ROTOR RESISTANCE
CONTROL [1]
Fig.2 gives the speed-torque characteristics of a slip-ring
induction motor for different values of rotor resistances.
Main drawback of the conventional scheme being
energy is dissipated in rotor circuit resistance, internal and
external. This energy is wasted in the form of heat. Because
of the waste-fullness of this method, it is used where speed
change are needed for short duration only.
FIG. 4 CHOPPER CONTROL SYSTEM [1]
Fig. 4 gives a chopper circuit with a second-order filter.
Removal of filter capacitor C and current limiting resistor
RC will make it a first-order filter.
With a second-order filter, one can use higher values of
R2. This permits a wide variation in speed-torque
characteristics of the drive. In fact, one can remove the
resistance R2 altogether.
A. Chopper Controlled System
With the advent of power semiconductors, the
conventional resistance control scheme can be eliminated
by using a three-phase rectifier bridge and a chopper
controlled external resistance as shown in Fig. 3.
181
International Journal of Emerging Technology and Advanced Engineering
Website: www.ijetae.com (ISSN 2250-2459, ISO 9001:2008 Certified Journal, Volume 4, Issue 7, July 2014)
With a filter in the rotor circuit, current waveforms can
be made continuous and ripple in the dc current can be
reduced to a very small value by selecting the appropriate
chopper frequency and corresponding parameters of the
filter circuit.
However, transfer functions that will be valid for small
perturbations may be derived under certain simplifying
assumptions, the parameters being dependent on the given
steady-state operating point. Thus an analysis for small
changes of speed about an operating point is attempted
below. The following simplifying assumption is made in
the dc circuit model given in the previous section.[10]
The voltage drop across stator impedance and voltage
loss due to commutation are negligible." With this
assumption, the torque developed by the motor under
steady-state becomes as given
B. DC Circuit
From (2), torque is a linear function of Id. This will hold
good only when the motor is not heavily loaded. For a
given duty cycle of the chopper, Id is proportional to slip S
and E is constant. However, for a given value of the slip,
current Id is a linear function of the duty cycle only when
T1 = T2, where
FIG. 5 DC CIRCUIT MODEL WITH BRIDGE RECTIFIER [3]
Fig. 5 gives a dc circuit model for the chopper-controlled
slip-ring induction motor with a filter in the rotor circuit.
From this model, the torque Td developed by the motor is
given by:
………. (1)
T1 rotor circuit time constant during ON mode,
T2 rotor circuit time constant during OFF mode
Where,
E
In a practical drive, it will not be possible to satisfy a
condition like T1 = T2. Considering this nonlinear
relationship between rotor current and the duty cycle of the
chopper.
dc output volt.of3 phase rectifier
E2
rms rotor voltage per phase (stand still)
r1
stator resistance/phase referred to rotor
Xlm
In the above equation, f(ei) is a nonlinear function of ei,
the input-to-PWM circuit which is proportional to the duty
cycle. R is the total resistance in the rotor circuit when the
switch is ON, and S is the motor slip.
For 100-percent duty cycle, f(ei) = 1. Hence,
(l1+l2) total leakage inductance referred to rotor
ω
supply frequency (Hz)
Id
average current in the dc link of rotor circuit
Ws
synchronous speed of motor (rad/s).
Id(max) = (E/R)S.
The above equation holds good under the following
assumptions:
1) The effect of ripple in the bridge rectifier output is
negligible.
2) The current in the dc circuit is perfectly smooth
To obtain the transfer functions for current and speed,
we will linearize the above equations around a reference
point.
Let the operating point be defined as Id = Ido, S = So, and
ei = ei0. Using a Taylor's series expansion of (4) around the
given operating point, and neglecting higher order terms,
the following linear equation is obtained:
C. Development Of Small Signal Model
The complete transient analysis of a conventional
induction motor is quite involved. The presence of a bridge
rectifier and chopper makes it all the more difficult.
Therefore, it is not possible to derive analytically a transfer
function that will be valid under all conditions.
182
International Journal of Emerging Technology and Advanced Engineering
Website: www.ijetae.com (ISSN 2250-2459, ISO 9001:2008 Certified Journal, Volume 4, Issue 7, July 2014)
Where
function
Where
internal speed feedback.
derivative at the reference point for the
,
represent perturbations around the operating
D. Block Diagram And Transfer Functions
Before developing a block diagram, the presence and
effect of various time constants in the system are
investigated.
point.
Since
Where
i] Chopper Time Constant: Although the duty cycle is
proportional to ei, the triggering of the thyristors is not
instantaneously corrected. There is a certain delay in the
actual change in the duty cycle and a change in the control
signal. Hence, the system should be treated as a sampled
data system. The triggering of the main thyristor
corresponds to sampling of ei. The amplitude of et at that
instant determines the duty cycle. The chopper does not
respond to any changes in ei until the next cycle. This
corresponds to a zero-order hold arrangement. Analysis can
be simplified by considering it as a simple first-order
system with a time constant Tc = T/2, where 1/T is chopper
frequency. Let
= motor speed, then
Let
, and
Substituting these relations in (5) gives
From (4)
From (5), (6) and (7)
The delayed change in duty cycle is represented by
ii] Filter Time Constant: A filter connected in the rotor
circuit to reduce the heating of rotor windings could be a
"first-order filter" or a "second-order filter". However,
during the ON mode of the main thyristor, both of them
will act as first-order filters with a time constant T1. It is
only during the OFF period that the second-order filter will
act as a second-order filter. [6] Let the filter parameters be
adjusted such that their effective time constant during the
OFF period is T2. Then
Let
Then ,
can be written as
From (3),
torque TL is
speed is given by
represents the effect of
. If the perturbation in load
, the perturbation in motor steady-state
With this, the effective time constant of the filter will be.
Where f is the coefficient of linear (viscous) friction of
load.
Substituting the value of ΔId from (8) gives
where
From (8) and (9), under steady-state
183
International Journal of Emerging Technology and Advanced Engineering
Website: www.ijetae.com (ISSN 2250-2459, ISO 9001:2008 Certified Journal, Volume 4, Issue 7, July 2014)
The chopper time constant Tc comes into the picture only
when the change in ei is being considered. However, the
filter time constant Tf is to be considered for changes in w
and also in ei. Considering these time constants, (6) and (8)
can be rewritten as
Let
(15) gives
. Substituting this in
From the block diagram
Considering the perturbations in speed and torque
Substituting for
from (16) yields
Where
is the mechanical time constant of load and
motor
J = moment of inertia of motor and load.
Effect of ∆TL
From the block diagram, if ∆TL is not zero, then
If ∆TL = 0
Equations (17) and (18) are the transfer functions for the
perturbations around the operating point. From the block
diagrams it can be observed that 1) the internal feedback
factor keb tends to make the current response more
oscillatory, and 2) if keb<<1,
, then the
transfer functions can be simplified to
The block diagram corresponding to (13)-(14) is given in
Fig. 6.
+
+
-
-
FIG. 6 CHOPPER-CONTROLLED SR-IM SMALL SIGNAL BLOCK DIAGRAM
iii] Derivation of
the block diagram of Fig.
and
: From
III. SIMULATION MODELS
A 3-hp slip-ring induction motor is used for simulations.
The speed control of this motor is obtained with rotor
chopper control as explained in the preceding sections.
Where
The two poles S1&S2 of this transfer function are given
by
184
International Journal of Emerging Technology and Advanced Engineering
Website: www.ijetae.com (ISSN 2250-2459, ISO 9001:2008 Certified Journal, Volume 4, Issue 7, July 2014)
Analysis of induction motor have been made for a speed
less than rated speed for 1000 rpm, by various modules
such as Speed Control of Induction Motor with
conventional rotor resistance scheme, Speed Control of
Induction Motor with chopper, Speed Control of Induction
Motor with chopper and filter controlled in open loop and
closed loop. Filter circuit is used to reduce voltage and
current spikes in open and closed loop scheme. A
resistance connected in the dc part of the rotor circuit was
used to obtain a current feedback signal in closed loop
scheme. The conventional testing methods were used to
determine the mechanical parameters of the slip-ring
motor.
Three phase Induction motor is tested with its full load
and rotor short circuited. Simulation in MATLAB
environment has been made, Simulation model is shown in
fig 7. Parameters like Speed, Torque, Stator & Rotor
Current are observed from simulations. Rotor speed of
SRIM is found to be 1440rpm with full load torque of
14.83N-m. Rated stator current noted from simulation
results 6.74Amp and rotor current found is 4.612Amp.
Simulated parameters are also shown in fig 8, 9, 10 & 11.
A. Slip Ring Induction Motor Parameters
3 phase slip ring induction motor
3 HP, 400 V RMS line-to-line, 50 Hz, 4 Pole
The stator and rotor resistance and inductance referred to
stator are
Rs = 0.7384 Ω; Ls = 3mH
Rr = 0.7402 Ω; Lr = 3mH
FIG. 8 SPEED OF SRIM WITH ROTOR SHORT CIRCUITED
The mutual inductance is Lm = 0.1241 H. The rotor
inertia is J = 0.0343 kg.m2
Torque = 14.85 N-m
Synchronous Speed Ns = 1500 rpm
Rotor Speed Nr = 1440 rpm
Slip = 4%, Rated Current Il = 5.38 Amp
No load Current Io= 0.5 Amp.
B. Slip Ring Induction Motor with rotor side short
circuited
FIG.9 TORQUE OF SRIM WITH ROTOR SHORT CIRCUITED
FIG. 10 STATOR CURRENT OF SRIM WITH ROTOR SHORT CIRCUITED
FIG. 7 SPEED CONTROL WITH ROTOR SIDE SHORT CIRCUITED
185
International Journal of Emerging Technology and Advanced Engineering
Website: www.ijetae.com (ISSN 2250-2459, ISO 9001:2008 Certified Journal, Volume 4, Issue 7, July 2014)
This arrangement will give proportional speed control
and will give improved speed regulation. Losses occur in
the form of heat dissipation in resistance.
FIG. 11 ROTOR CURRENT OF SRIM WITH ROTOR SHORT CIRCUITED
C. Slip Ring Induction Motor with conventional rotor
resistance scheme
FIG. 13 SPEED OF CONVENTIONAL ROTOR RESISTANCE SCHEME
FIG. 14 TORQUE OF CONVENTIONAL ROTOR RESISTANCE SCHEME
FIG. 12 SPEED CONTROL WITH CONVENTIONAL ROTOR RESISTANCE
SCHEME
Speed Control of SRIM can be done with conventional
rotor resistance scheme. Speed can be reduced from rated
speed to desire by adding external resistance in the slip
rings of rotor. Resistance of 20Ω is added in each phase to
achieve speed of 1000rpm.Simulation in MATLAB
environment has been made for full load torque condition.
Parameters like Speed, Torque, and Stator & Rotor Current
are noted. Rotor speed of SRIM with conventional scheme
is found to be 1000rpm with full load torque of 14.83N-m.
Stator current noted from simulation results is 6.74Amp
and rotor current found is 4.15Amp. Power Consumption in
the rotor circuit is 200.4W.
Energy Consumption in the rotor circuit is calculated
considering motor is running for 8hrs.Simulated values are
reported in table no II. Simulated parameters are also
shown in fig 13, 14, 15 and 16.
FIG. 15 STATOR CURRENT OF CONVENTIONAL ROTOR RESISTANCE
SCHEME
186
International Journal of Emerging Technology and Advanced Engineering
Website: www.ijetae.com (ISSN 2250-2459, ISO 9001:2008 Certified Journal, Volume 4, Issue 7, July 2014)
Stator current noted from simulation results is 6.1Amp
and rotor current found is 1.1Amp. Power Consumption in
the rotor circuit is 120.75W.
Energy Loss in the rotor circuit is calculated for
simulated values considering motor is running for 8hrs.
Simulated values are reported in table no II. Simulated
parameters are also shown in fig 18, 19, 20 and 21.
Losses are still there, but the losses can be minimized if
we implement filter in the circuit. Care is taken to make
controller response as fast as possible.
FIG. 16 ROTOR CURRENT OF CONVENTIONAL ROTOR RESISTANCE
SCHEME
D. Slip Ring Induction Motor with chopper scheme
FIG. 18 SPEED OF SRIM WITH CHOPPER SCHEME
FIG. 17 SPEED CONTROL WITH CHOPPER SCHEME
FIG.19 TORQUE OF SRIM WITH CHOPPER SCHEME
In this scheme Chopper is used with GTO as a switch.
Simulation Model is shown in fig 4.0.External resistance is
inserted periodically, when chopper switch is ON
resistance is taken out. Continuous energy loss in resistance
of rotor circuit with previous scheme is minimized. By
adjusting the duty cycle of chopper and pulse width of
pulse generator, speed is controlled and adjusted to
1000rpm. This arrangement will give proportional speed
control and will give improved speed regulation.
Simulation in MATLAB environment has been made for
full load torque condition. External resistance is inserted
and taken out with the help of chopper switch. GTO is
acting as a switch. Parameters like Speed, Torque, Stator &
Rotor Current, and Power are noted from the simulated
values. Rotor speed of SRIM with Chopper scheme is
found to be 1000rpm with full load torque of 14.83N-m.
FIG. 20 STATOR CURRENT OF SRIM WITH CHOPPER SCHEME
187
International Journal of Emerging Technology and Advanced Engineering
Website: www.ijetae.com (ISSN 2250-2459, ISO 9001:2008 Certified Journal, Volume 4, Issue 7, July 2014)
Speed of Induction Motor is controlled, by chopper
control and Parameters like Speed, Torque, Stator & Rotor
Current, and Power are noted from the simulated values.
Rotor speed of SRIM with Chopper in open loop along
with filter scheme is adjusted at 1000rpm by adjusting the
duty cycle of chopper. With full load torque of 14.83N-m,
Stator current noted from simulation results is 6.1Amp and
rotor current found is 1.1Amp. Now the power loss at rotor
side is 53.13W which is reduced to 56 % as compared to
chopper circuit.
Energy Loss in the rotor circuit is calculated considering
motor is running for 8hrs. Simulated values are reported in
table no II. Simulated parameters are also shown in fig 23,
24, 25 and 26.
FIG. 21 ROTOR CURRENT OF SRIM WITH CHOPPER SCHEME
E. Slip Ring Induction Motor with open loop filter
FIG. 23 SPEED OF SRIM WITH CHOPPER IN OPEN LOOP
FIG. 22 SPEED CONTROL WITH OPEN LOOP FILTER
Speed of SRIM can be controlled with chopper
implemented with filter in open loop. The simulation model
with this technique is shown in fig 22
In this scheme Chopper is used with SCR as a switch,
Continuous energy loss in resistance of rotor circuit with
conventional scheme is minimized. By adjusting the duty
cycle of chopper along with pulse width of pulse generator
and appropriate selection of filter parameters gives
proportional speed control and will give improved speed
regulation.
The simple arrangement for controlling the average
value of rotor current (external resistance) introduces the
additional problems of discontinuity in the rotor winding
currents and voltage spikes across the chopper thyristor.
These problems could be taken care of by having either a
first- or second-order filter in the rotor circuit. Here filter
circuit is used in open loop, Simulation in MATLAB
environment has been made for full load torque condition.
FIG. 24 TORQUE OF SRIM WITH CHOPPER IN OPEN LOOP
188
International Journal of Emerging Technology and Advanced Engineering
Website: www.ijetae.com (ISSN 2250-2459, ISO 9001:2008 Certified Journal, Volume 4, Issue 7, July 2014)
However, with a thyristor chopper in the rotor circuit, an
induction motor may now be applied in closed-loop drives
with a good degree of precision. A chopper with filter is
connected on the rotor side of a three-phase slip-ring
motor. The rotor current is sensed by connecting a small
resistance in the dc circuit. The duty cycle of the chopper
circuit is controlled by varying ei, the output of the current
controller. A simple arrangement of proportional speed
control with current limit will also give improved speed
regulation with protection for excessive currents during
starting and under overload conditions
Simulation Model of SRIM with Closed Loop Control Is
shown in fig 27 Simulation in MATLAB environment has
been made for full load torque condition. Rotor chopper
control along with second order filter is used in closed loop
scheme. The rotor resistance-controlled slip-ring induction
motor has very poor speed regulation with open-loop
control..
A proportional-integral (PI) controller to get almost zero
steady-state error. The speed controller output has an
adjustable saturation level, which sets the reference for the
current control loop. There is a second PI controller for
current control. The current control loop maintains constant
current against disturbances in supply voltage. Moreover,
this provides fast response compared to the current limit
arrangement. During starting and under overload
conditions, the output of the speed controller limits the
rotor current to a preset reference value. The starting
current and, hence, starting torque can be adjusted by
adjusting the saturation level of the output of the speed
controller.
Speed Control of SRIM is achieved as desired, by setting
the desired reference value. Parameters like Speed, Torque,
Stator & Rotor Current, and Power are noted from the
simulation.
Chopper in closed loop along with filter and PI
Controller is implemented to achieve speed of 1000 rpm.
With full load torque of 14.83N-m, Stator current noted
from simulation results is 7.2Amp and rotor current found
is 0.1025Amp. Now the power loss at rotor side is 5W
which is reduced to 96 % as compared to chopper-filter
circuit in open loop. Energy Consumption in the rotor
circuit is calculated for simulated values considering motor
is running for 8hrs. Simulated values are reported in table
no II. Simulated parameters are also shown in fig 28, 29, 30
and 31.
FIG. 25 ROTOR CURRENT OF SRIM WITH CHOPPER IN OPEN LOOP
FIG. 26 ROTOR CURRENT OF SRIM WITH CHOPPER IN OPEN LOOP
F. Slip Ring Induction Motor with closed loop filter
FIG. 27 SPEED CONTROL WITH CLOSED LOOP FILTER
In many industrial applications, very good speed
regulation of the drive is essential. In such cases, it
becomes necessary to employ closed-loop speed control.
Precision closed-loop regulators for conventional rotor
resistance control are impractical.
189
International Journal of Emerging Technology and Advanced Engineering
Website: www.ijetae.com (ISSN 2250-2459, ISO 9001:2008 Certified Journal, Volume 4, Issue 7, July 2014)
FIG. 31 ROTOR CURRENT OF SRIM WITH CHOPPER IN CLOSED LOOP
FIG. 28 SPEED OF SRIM WITH CHOPPER IN CLOSED LOOP
Speed Control of SRIM can be achieved using various
techniques. While achieving the required speed losses
occur at rotor side. It is the power that is wasted whenever
machine speed is brought below rotor speed. Certain
applications requiring high torque require speed less than
rated speed. Here we have compared various techniques
for speed control.
Analysis is made assuming motor to run for 8 hours.
Energy Consumption is calculated for 8 hours. It is the
energy which is wasted at rotor side if motor runs for long
time.
When the speed is controlled with the conventional
scheme energy wasted in the rotor is around 1603.2 W-hr.
To minimize this loss new power electronics based
techniques are implemented. When speed of SRIM is
controlled with chopper, the power loss is reduced by 40%,
But still there are voltage spikes and discontinuity in rotor
winding currents so chopper with open loop scheme is
implemented. Now the power loss is again reduced by 56%
as compared to chopper circuit. When the closed loop
scheme along with filter and PI controller is used for the
same desired speed losses are reduced to around 96% as
compared to previous schemes.
FIG. 29 TORQUE OF SRIM WITH CHOPPER IN CLOSED LOOP
FIG. 30 ROTOR CURRENT OF SRIM WITH CHOPPER IN CLOSED LOOP
190
International Journal of Emerging Technology and Advanced Engineering
Website: www.ijetae.com (ISSN 2250-2459, ISO 9001:2008 Certified Journal, Volume 4, Issue 7, July 2014)
TABLE I
SIMULATION VALUES OF SRIM WITH DIFFERENT TECHNIQUES
Sr Parameters
N.
Acknowledgement
The authors are grateful to the Department of Electrical
Engineering of the Priyadarshini College of Engineering,
Nagpur, for making available experimental and computing
facilities.
Conventio Chopper Chopper Chopper
nal rotor
in Open in Closed
resistance
Loop
Loop
1 Speed (RPM)
1,000
1,000
1,000
REFERENCES
1,000
[1]
2 Torque (N-m)
14.83
14.83
14.83
14.83
3
Stator Current
(A)
6.74
5.8
6.1
7.2
4
Rotor Current
(A)
4.15
2.5
1.1
0.1025
5
Power loss in
rotor (W)
200.4
120.75
53.13
5
6 Speed (RPM)
1,000
1,000
1,000
1,000
M. Ramamoorthi, Senior Member IEEE and NS Wani, Member
IEEE “Dynamic Model for Chopper Controlled Slip-Ring Induction
Motor”
IEEE Trans. On Industrial Electronics and control
Instrumentation., vol. IECI-25 ,no. 3, Aug. 1978.
[2] M. Ramamoorty and N. S. Wani, "Chopper controlled slip-ring
induction motor with closed loop control," IEEE Trans. Ind.
Electron. Contr. Instrum., vol. IECI-24, pp. 153-161, May 1977.
[3] N. S. Wani, "Thyristor controllers for slip-ring induction motors,"
Ph.D. dissertation (under completion), Dep. Elec. Eng., Indian
Institute of Technology, Kanpur, India.
[4] Miljanic, "The through-pass inverter and its application to the speed
control of wound rotor induction machines," IEEE Trans.
PowerApp. Syst., vol. PAS-87, pp. 234-239.
[5] P. C. Sen and K. H. J. Ma, "Rotor chopper control for induction
motor drive TRC strategy," IEEE Trans. Id. Appl. vol. IA-i1, pp.4349.
[6] M. Gottfried, Line Communicated Thyristor Converters. New York:
Pitman, 1972.
[7] P. L. Alger, “Induction Machines”, 2nd Edition, Gordon and Breach
Science Publishers, 1970.
[8] 121 G. H. Rawcliffe, R. F. Burbidge and W. Foiig, “InductionMotor Speed-Changing by Pole-Amplitude Modulation”, IEEE
PROC., Vol. 105, NO. 8, Aug. 1958, pp. 411
[9] Dr. Ing O. Iodoro and Dr. Mu. Agu, “Induction motor control
strategies: past & present” The specific journal of Science & Tech.,
vol 6, No.1, May 2005
[10] Leson S., Smaia Ms. Shepherd W. “Control of wound rotor
induction motor using thyristor in secondary circuits” Industrial
Application conference 28 IAS, Annual meeting of IEEE, 1993
Vol -1
[11] HilmiFadhil Amin. “High Chopper Frequency Drive of wound rotor
induction motor with a resistively loaded rotor chopper” Dep. Elec.
Eng, Salahaddin University- Erbil.
IV. SIMULATION MODELS
Speed Control of slip ring induction motor by
implementing rotor chopper control is studied by using
various techniques. Conventional method is compared with
power electronic circuitry based schemes. Losses are
reduced as new techniques are implemented.
Closed loop scheme gives proportional speed control
with current limit. It also provides improved speed
regulation with protection for excessive currents during
starting and under overload conditions. This scheme gives
very good speed regulation of the drive and the power loss
is reduced by 97% as compared with the conventional rotor
resistance scheme and by 96% as compared with chopper
open loop control scheme.
191