Investigations in to Induction Motor Drive using Slip
Power Recovery Scheme with GTO Inverter and
Chopper
Sita Ram*1, O. P. Rahi*2, Veena Sharma*3, and K. S. R. Murthy*4
1
*EED NIT Hamirpur (HP), India.
srbhrdj@gmail.com, 2oprahi2k@gmail.co.in, 3veenanaresh@gmail.com, and 4harikella96@gmail.com
Abstract—Induction motors are used as industrial drive due
to their rugged and simple construction as well as low
maintenance. The speed control of slip ring induction motor
(SRIM) is accomplished by slip power recovery scheme consisting
of inverter control, chopper control, and rotor resistance control
techniques. This article presents the improvement in the
performance characteristics of SRIM drive offered by GTO
inverter and buck-boost chopper based slip power recovery
scheme (SPRS). The simulation model of a 2 hp SRIM drive
using Silicon controlled rectifier (SCR) and gate turned off
(GTO) inverter control and GTO based buck-boost chopper
control has been established in the SIMULINK environment.
The simulation results using inverter control and chopper control
have been analyzed and compared. The power factor, efficiency
and total harmonic distortion have been taken as parameters for
analyzing the enhancement in the performance of the SRIM
drive. The simulation results have shown that GTO based
inverter chopper controlled SPRS has higher power factor,
efficiency and lower THD compared to SCR inverter controlled
SPRS.
Keywords—chopper; GTO; efficiency; induction motor; power
factor; SCR; slip power recovery scheme;
I. INTRODUCTION
Slip ring induction motor (SRIM) are used in the industrial
field where the drive operation is intermittent i.e. hoists, cranes,
conveyers, and lifts because the slip power can be easily
controlled by slip rings. The slip power recovery scheme
(SPRS) controls the speed of SRIM by sending back the
feedback power to the supply mains thereby improves the
efficiency of the SRIM drive [1]. SRIM drive operates at
limited speed range and has slip power a smaller part of motor
power rating, hence low rating of converter and lower cost [2].
The researchers are drawing more interest in the field of
renewable energy sources because of advancement in the static
converters technology [3-4]. The major setback of SPRS has
been found to be as i) poor power factor of the supply, ii)
requirement of higher reactive power and iii) high harmonic
components [5-6]. The existence of harmonic contents
produced the distortion in the supply source.
In literature numbers of methodologies [7] have been
reported to improve the performances of the slip power
recovery drive (SPRD). A methodology employing buck
chopper has operated the inverter at most secure firing angle
and decrease the reactive power consumption of inverter in
978-1-5386-4318-1/17/$31.00 ©2017 IEEE
this manner improve the power factor and efficiency of SRIM
drive [8]. The different circuit configurations of PWM inverter
and boost chopper have been utilized in the DC link of SPRS to
control active and reactive power and also decrease the
harmonics of rotor side [9, 10]. The utilization of boost/buckboost chopper has replaced one of the insulated gate bipolar
transistor (IGBT) converters from the rotor circuit side by
silicon controlled rectifier (SCR) converter and decreases the
cost of SPRS with the same performance indices of induction
machine [11]. Theoretically the mathematical model has been
drawn to evaluate the DC link of SPRD [12]. A twelve pulse
SCR inverter with IGBT boost chopper has been exercised to
enhance the power factor, while SPRD utilizing voltage source
inverter (VSI) and boost chopper applying voltage control
technique and current control technique decrease the total
harmonic distortion (THD) of source and improved the power
factor [13-15]. A SPRD system using buck converter and
inverter with three PWM techniques in the intermediate circuit
has been used with LC filter to decrease the harmonic contents
of supply source [16]. The inverter configuration with stepdown and step-up/down chopper has enhanced the power factor
and efficiency of the SRIM drives and quality of power supply
[17, 18].
II. MATHEMATICAL MODELING OF SPRS
This part of the section describes the mathematical
modeling of conventional SPRS.
A. Circuit Model of the Conventional SPRS
In the SPRS shown in “Fig. 1,”, the three phase full-wave
diode bridge rectifier is connected to the rotor windings
through slip rings and converts the slip power in to DC.
R
Y
B
Three Phase Supply
M
L
Induction Motor
Recovery Transformer
Id
Speed
D1 D 3 D 5
S2
D4
Vd1
D6 D 2
T1
T3
T5
T4
T6
T2
Vd2
S1
(90° < α < 180°)
Rotor Resistance Starter
Diode Bridge
Inverter Bridge
Fig. 1. Schematic diagram of SPRS using SCR inverter bridge
A three-phase natural commutated SCR inverter inverts the
DC power into line frequency AC and feedback the same to
the source which can be controlled by controlling the inverter
emf Vd 2 , by varying the firing angle of the inverter. The DC
link inductor Ld in the intermediate circuit reduces the swells
in DC link current I d and the transformer match the voltages
Vd 1 and Vd 2 by taking a suitable turns ratio. Ignoring the
stator and rotor drops,
3 2
Vd 1
S
u
sV
sV
Ÿ 1.35 u
n
n
3 2 V
V
u cos D Ÿ 1.35 u cos D
S
m
m
Vd 2
(1)
(2)
where Vd 1 and Vd 2 are the diode bridge and inverter-bridge
output voltages, D = the inverter firing angle, m = the turns
ratio of transformer from source to converter side, n = the
turns ratio of induction motor from stator to rotor side, s = the
slip, V = the input voltage. Extreme value of D is confined
to 165 q for secure commutation of thyristors. The desired
speed can be obtained with proper choice of D [19].
The equations for slip, DC link current, air gap power, and
electromagnetic or developed torque are given by (3), (4), (6)
and (10) below [18]
s
Id
n
cos D
m
Vd 1 Vd 2
2( sRs' Rr ) Rd
Vd 2 I d Ÿ 1.35 u
1.35
Pm
(4)
Vd 2
V
cos D u I d
m
(5)
Ÿ Pm
Td u Zm 1 s
2
p
The electromagnetic torque is given by
p Pg
u
Td
2 Zm
(7)
(8)
Rdc
(14)
3( X sc X r ) ½
­
®2 Rsc ¾ s Rr Rd
S
¯
¿
(15)
R
Y
(9)
where, I dc is DC link current, Rs' is stator resistance referred
to rotor side, Rr is rotor resistance, Rd is resistance of DC link
(13)
where, G = duty ratio of chopper and Rdc = the DC link circuit
resistance that can be expressed as [13]
B
From equations (7) and (10), electromagnetic torque can be
written as
§ p · 1.35V
u Id
Td ¨ ¸
(10)
© 2 ¹ n u Zm
(12)
Vd 1 Vd 2
Rdc
Id
(6)
Td u Zr
§ G ·V
1.35 ¨
¸ cos D
© 1 G ¹ m
n§ G ·
¨
¸ cosD
m © 1 G ¹
s
V
u Id
n
1 s Pg
B. Model of Proposed SPRS using GTO Inverter and BuckBoost Chopper
The shortcoming of the conventional SPRS is the large
reactive power consumption of the inverter from the source
when firing angle increases above 90°, which reduces power
factor and enlarge the total harmonic distortion (THD) of the
source. To sort out this problem the proposed scheme has
introduced the buck-boost chopper controller as shown in “Fig.
2,” which control the motor speed by duty ratio control and
setting the firing angle to a value drawing minimum reactive
power from the source. In this way the proposed scheme
decreases the reactive power drawn from the source by the
inverter consequently, improve the source power factor and
reduced the THD of the source current.
(3)
From equations (4) and (6)
Pg
Equation (11) indicates that the torque is directly
proportional to DC link current and the magnitude depends
upon the difference between the Vd 1 and Vd 2 . Therefore torque
speed characteristics of SRIM drives are nearly linear as that of
separately excited DC motor for a particular constant value of
firing angle α.
Taking in to consideration the DC link equivalent circuit of
“Fig. 2,” the DC voltage of inverter, slip and DC link current
can be written as [18]
Neglecting copper loss
sPg
inductor, Pg is power in the air gap, Td is electromagnetic
torque, Pm is mechanical power developed, Zm and Zr are the
synchronous speed and rotor speed in rad/sec, p is no of poles
[20].
Induction
Motor
Three Phase Supply
Recovery Transformer
L
Id
M
Speed
S2
S1
D1 D 3 D 5
Vd1
D4 D6 D 2
S1
Lc
IGBT
Dc2
T1
S2
Dc1
IGBT
C
Vc
T3
T5
Lf
Vd2
Rotor Resistance Starter Diode Bridge Buck-Boost Chopper
T4
T6
Cf
T2
Inverter Bridge
LC Filter
Fig. 2. Schematic diagram of SPRS employing SCR inverter with buck-boost
chopper
Air gap power, motor torque, and power factor are given by
Firing Angle
Pulse Generator
95
Mean
In
alpha_deg
a
sPg
Vd 2 I d Ÿ Pg
(16)
s
Gain
speed in rpm
powergui
ir_abc
Cm
+
Discrete,
Ts = 5e-006 s.
-K -
Motor Measurement
c
Vd 2 I d
Mean Value
Firing Pulses
Pulse
b
is _abc
i
-
m
wm
Sm
Te
Scope 1
Ss
Torque
10
m
Tm
Filter
[A]
T
Zm
Ÿ
Vd 2 I d
(17)
sZm
Cs
i
+ -
Goto
Pg
cosI =
( Ps Pr ) (Qs Qr )
2
a
B
b
C
c
g
p
a
b
c
N
Induction Motor
+
A
B
Vb
C
Diode Bridge
i
-
Vc
+
[B]
(18)
+
-
V
Mag_V_I
Gain 2
[A]
From 1
magnitude
signal
angle
Fourier 1
c
Transformer
V
I
P_Q
Source Reactive Power
Discrete
Active & Reactive
Power 1
Source Active Power 1
T2
Source Active Power
Mag_V_I
v
P_Q
Discrete
Active & Reactive
Power 2
Feedback Current
(Amps)
Gain 1
Source Current
(Amps )1
Source Reactive Power
1
[B]
From 6
-K -
magnitude
signal
angle
Fourier
T1
Gain 3
-K T
sin(u)
cos(u)
sin(u)
-K -
b
C
v
I
where X sc = reactance of stator referred to rotor side and X r =
reactance of rotor respectively. Ps = active power and Qs =
reactive power consumed by inverter and motor from the
supply source. Pr = active power recovered by inverter and Qr
= reactive power taken/recovered by the inverter from the
supply source and is written as
+
-
Sfb
Primary Voltage 2
a
B
T3
Primary Voltage 1
Cfb
Goto 1
2
A
-
Inverter Bridge
Va
( Ps Pr )
A
Cos
cos(u)
Cos1
Feedback power
factor
Source power
factor
Fig. 3. Circuit model of SPRS employing SCR inverter without chopper
The rotor speed in rad/sec can be determined by [20]
N
(25)
Zr 2S u r
60
Pr
§ G
1.35V ¨
© 1 G
·
¸ cosα u I d
¹
(19)
Qr
§ G
1.35V ¨
© 1 G
·
¸ sinα u I d
¹
where, TL = load torque in Nm , N r = rotor speed (rpm), K1 =
the %age efficiency.
(20)
Proposed model of SPRS shown in “Fig. 4,” is simulated in
SIMULINK. The speed of SRIM is varied by varying dutyratio δ from 80%-30% at an interval of 3% and fixing the firing
angle of inverter at α = 91°. The observed results have been
plotted as shown in “Fig. 10,”–“Fig. 14,”.
Equation (20) shows that the reactive power drawn from
the source can be decreased by decreasing duty ratio keeping
firing angle fixed which in turn increases the power factor as
represented by equation (18). Hence the proposed scheme
improves the power factor.
III. MODELING AND SIMULATION OF SPRS
The SPRS employing the SCR inverter as shown in “Fig.
3,” has been simulated in Simulink. The measurement blocks
like Fourier block, and discrete block have been used to
measure the speed, rms value of current, power factor of the
current and the active and reactive power drawn from the
source. The model of SRIM of rating 2 hp, 415V, 50Hz, 1430
rpm has been simulated employing SCR inverter bridge. The
model is running on MATLAB and different observations are
plotted as shown in “Fig. 5,”-“Fig. 9,” at various firing angle α
of the inverter bridge. The efficiency and input-output powers
can be described as in (22)-(25) below. The percentage
efficiency of SRIM can be expressed as
Pout
K1
u100
(21)
Pin Pfb
where, Pin = power input (W) and Pfb = power feedback (W)
and can be calculated as
Pin
3 u Ps
(22)
Pfb
3 u Pfbc
(23)
where Ps = source active power/phase (W) and Pfbc = feedback
power/phase measured (W) from the measurement blocks,
additionally the mechanical power at the shaft (W) can be
expressed by
Pout
Zr u TL
(24)
Fig. 4. Circuit Model of SPRS employing GTO inverter and buck-boost chopper
IV. SIMULATION RESULTS AND DISCUSSION
This section includes the simulation results obtained from
Simulink of 2 hp SRIM. The results of “Fig. 5,”–“Fig. 9,”
show the characteristics of SRIM using SPRS with SCR
inverter control technique.
A. Firing angle vs. speed
Simulation has been carried for one second and constant
load of 8 Nm was applied to the SRIM. The variations of
speed by varying the firing angle obtained from simulations
have been shown in “Fig. 5,”. The simulation results have
shown that with the increase in firing angle the rotor speed
decreases and vice versa.
B. Firing anggle vs. feedback power
Simulation results for inverter firing angle and feedback
power have been shown in “Fig. 6,”. The result indicated that
as the firing angle increases the feedback power also increases.
For the constant load increase in feedback power, decreases the
power drawn from the source consequently, enhance the
efficiency of the drive.
C. Firing angle vs. source power factor
The graph of firing angle and source power factor has been
shown in “Fig. 7,”. From the graph it is clear that there is
decrease in source power factor with increase in firing angle, of
inverter. From the simulation results the average value of
power factor is found to be 0.72.
Fig. 8. Graph of firing angle vs. efficiency
D. Firing angle vs. efficiency
The graph of firing angle and efficiency has been shown in
“Fig. 8,”. From the graph it is evident that as the firing angle
increases the efficiency increases. The average value of
efficiency recorded as 84.3%. The increase in firing angle
increases the feedback power which in turn reduces the power
drawn from the source for constant load hence increases the
efficiency.
Fig. 5. Graph of firing angle vs. speed
Fig. 9. Graph of firing angle vs. THD
E. Firing angle vs. THD
“Fig. 9,” shows the variations of the THD for different
firing angles of inverter. It has been observed from the graph
that with the increase in firing angle of inverter, THD of the
supply increases in case of inverter control. It is seen that the
increase in firing angle above 90°, the inverter increases the
reactive power consumption of inverter resulting in increase in
THD of the supply. The average value of THD recorded from
simulation results is 42.54%.
The characteristics of SPRS with GTO inverter and
chopper control technique obtained from Simulink
environment for 2 hp SRIM drive have been shown in “Fig.
10,” –“Fig. 14,”.
F. Duty ratio vs. speed
The graph of duty ratio and rotor speed has been shown in
“Fig. 10,”. From the graph it has been observed that the
increase in duty ratio increases rotor speed and vice versa.
Fig. 6. Graph of firing angle vs. feedback power
Fig. 7. Graph of firing angle vs. source power factor
G. Duty ratio vs. feedback power
The variation of feedback power with respect to duty ratio
has been shown in “Fig. 11,”. The feedback power increases
with decrease in duty ratio. The rate of increment in feedback
power shown by “Fig. 11,” (duty ratio control) is more than by
“Fig. 6,” (firing angle control). Hence chopper control
technique has better efficiency.
H. Duty ratio vs. source power factor
The graph between duty ratio and source power factor has
been shown in “Fig. 12,”. Source power factor decreases with
the decrease in duty ratio, but the slope of this graph is less
compared to graph shown in “Fig. 7,”. This is because the
chopper control reduces the reactive power consumption of
the inverter and increases the active feedback power to the
source, so has higher power factor. In this control technique
the average power factor is recorded as to be 0.89.
increases as duty ratio decreases because more power is
feedback to the source. The average value of efficiency using
chopper control is found to be 87.55%.
Fig. 10. Graph of duty ratio vs. speed
J. Duty ratio vs. THD
The variation of THD with respect to duty ratio has been
shown in “Fig. 14,”. THD increases with decrease in duty ratio
and average value is found to be 5.29%. But the increase in
THD is less compared to inverter control method shown in
“Fig. 9. Hence chopper control has reduced the THD by a
margin of 87.56% from inverter control.
The comparative graph of power factor and efficiency
using inverter and chopper control methodologies have been
illustrated by “Fig. 15,” and “Fig. 16,”. “Fig. 17,” shows the
comparative graph of THD without and with chopper
controller. The results have been compared based on the equal
speed range and load torque for SRIM drive.
Fig. 11. Graph of duty ratio vs. feedback power
K. Speed vs. source power factor
The relative graph of speed and power factor for inverter
and chopper control techniques have been shown in “Fig. 14,”.
Power factor of SCR inverter control has been indicated by
cos I1 having average value of 0.67 and chopper control by
cos I2 with average value of 0.89. Therefore the chopper
control technique enhances the power factor by 32.84% that
from the inverter control technique.
Fig. 12. Graph of duty ratio vs. source power factor
Fig. 15. Graph of speed vs. power factor without and with chopper control
Fig. 13. Graph of duty ratio vs. efficiency
Fig. 16. Graph of speed vs. efficiency without and with chopper control
Fig. 14. Graph of duty ratiovs. THD
I. Duty ratio vs. efficiency
The graph of duty ratio and efficiency has been shown in
“Fig. 13,”. From the graph it is seen that the efficiency
Fig. 17. Graph of speed vs. THD without and with chopper control
L. Speed vs. efficiency
The relative graph of speed vs. efficiency has been shows
in “Fig. 15,”. In this graph K1 designates the percentage
efficiency of SPRS employing the SCR inverter control
having average value of 82% and K 2 the percentage efficiency
employing the chopper control having average value of
86.5%. Hence chopper control technique improves the
efficiency of the SRIM drive by the margin of 5.48% from the
inverter control technique.
M. Speed vs. THD
The relative graph between speed and THD with inverter and
chopper control techniques has been illustrated by “Fig. 16,”.
The THD-1 indicates the THD of source with inverter control
methodology having average value of 47.63% and THD-2, the
THD of source with chopper control having average value of
5.43%. The chopper control has lowered the THD of supply
source by a margin of 88.89% from the inverter control
technique.
V. CONCLUSIONS
The performance of SRIM drive has been presented in this
paper using SCR inverter control and GTO based inverter with
chopper controlled SPRS. The proposed SPRS using inverter
control, and chopper control methodologies have been
simulated in the simulink. The power factor, efficiency and
THD have been taken as parameters to examine the
enhancement in performance of SRIM drive. The simulation
results have indicated that the GTO inverter and chopper
control technique enhances the average power factor by
margin of 32.84% and efficiency by 5.48% than by SCR
inverter control technique. Similarly the GTO inverter and
chopper control technique has decreases the average THD of
supply source by 88.89% from the SCR inverter control
technique. These results have suggested that the application of
SRIM drive using SPRS with GTO inverter and chopper
control has superior performances than with SCR inverter
control.
REFERENCES
[1]
[2]
[3]
R. Ajabi-Farshba and M. R. Azizian, “Slip power recovery of induction
machines using three-Level T -type converters,” IEEE 5 th Conference on
Power Electronics, Drive Systems and Technologies, pp. 483-486, Feb
5-6, 2014.
X. Yang, L. Xi, X. Yang, and Jian-guo Jiang, “Research on the
application of PFC technology in cascade speed control system,” IEEE
3rd Conference on Industrial Electronics and Applications ICIEA, pp.
1964-1969, 3-5 June, 2008.
O. P. Rahi and A. K. Chandel, “Refurbishment and Uprating of Hydro
Power Plants-A Literature Review,” Renewable and Sustainable Energy
Reviews, vol. 48, pp. 726-737, August 2015.
[4]
[5]
[6]
[7]
[8]
[9]
[10]
[11]
[12]
[13]
[14]
[15]
[16]
[17]
[18]
[19]
[20]
O. P. Rahi and A. Kumar, “Economic Analysis for Refurbishment and
Uprating of Hydro Power Plants,” Renewable Energy, vol. 86, pp. 11971204, 2016.
A. Lavi and R. J. Polge, “Induction motor speed control with static
inverter in the rotor,” IEEE Transaction on Power Apparatus and
Systems, vol. PAS-85, pp. 76-84, 1966.
W. Shepherd and J. Stanway, “Slip power recovery in an induction
motor by the use of a thyristor inverter,” IEEE Transactions on Industry
and General Applications, vol. IGA-5, no. 1, pp. 74-82, 1969 .
Sita Ram, O. P. Rahi, and Veena Sharma, “A comprehensive literature
review on slip power recovery drives,” Renewable and Sustainable
Energy Reviews, vol. 73, pp. 922-934, 2017.
P. Pilley and L. Refoufi, “Calculation of slip energy recovery induction
motor drive behavior using the equivalent circuit,” IEEE Transactions
on Industry Applications, vol. 30, no. I. pp. 154-163, January/February
1994.
G. D. Marques, “Numerical simulation method for the slip power
recovery system,” IEEE Proceedings of Electronic Power Application,
vol. 146, no. 1, pp. 17-24, January 1999.
G. D. Marques and P. Verdelho, “A simple slip-power recovery system
with a dc voltage intermediate circuit and reduced harmonics on the
mains,” IEEE Transactions on Industry Electronics, vol. 47, no. 1, pp.
123-132, Feb. 2000.
D. Panda, E. L. Benedict, G. Venkataramanan, and T. A. Lipo, “A novel
control strategy for the rotor side control of a doubly-fed induction
machine,” IEEE Conference Record of 36th Annual meeting of Industry
Applications, vol. 3, pp. 1695-1702, 30 September-4 October 2001.
A. K. Mishra and A. K. Wahi, “Performance analysis and simulation of
inverter fed slip -power recovery drive,” IE (I) Journal-EL, vol. 85, pp.
89-95, Sept. 2004.
S. Tunyasrirut, J. Ngamwiwita, V. Kinnares , T. Furuya, and Y.
Yamamotod, “A DSP-based modified slip energy recovery drive using a
12-pulse converter and shunt chopper for a speed control system of a
wound rotor induction motor,” Electric Power Systems Research, vol.
78, no. 5, pp. 861–872, 2008.
S. Tunyasrirut , V. Kinnares, and J. Ngamwiwit, “Performance
improvement of slip energy recovery system by a voltage controlled
technique,” Renewable Energy, vol. 35, pp. 2235-2242, 2010.
S. Tunyasrirut and V. Kinnares, “Speed and power control of a slip
energy recovery drive using voltage-source PWM converter with current
controlled technique,” 10th Eco-Energy and Materials Science and
Engineering Symposium, vol. 34, pp. 326-340, 2013.
C. Pardhi, A. Yadavalli, S. Sharma, and G. A. Kumar, “A study of slippower recovery schemes with a buck dc Voltage intermediate circuit and
reduced harmonics on the mains by various PWM techniques,”
International Conference on Computation of Power, Energy,
Information and Communication, pp. 495-499, 2014.
S. Ram, O. P. Rahi, V. Sharma, and A. Kumar, “Performance analysis
of slip power recovery scheme employing two inverter topologies,”
Proceedings of MFIIS, vol. 2, pp. 356-361, 12-13 September 2015.
Sita Ram, O. P. Rahi and Veena Sharma, “ Analysis of induction motor
drive using buck-boost controlled slip power recovery scheme,” IEEE
International Conference on Power Electronics, Intelligent Control and
Energy Systems, pp. 1985-1990, 4-6 July, 2016 DTU.
G. K Dubey, “Fundamentals of Electrical Drives,” 1995, Narosa Public
House Delhi.
N. Mohan, T. M. Undeleand, and W. P. Robbin, “Power electronics
converters, aplications, and design.” Third Edition, Willey India Pvt.
Ltd. New Delhi 2014.