Progress In Science and Engineering Research Journal
ISSN 2347-6680 (E)
Performance Improvement of Three Phase Squirrel Cage
Induction Motor using Modified Stator Winding
Surinder Pal1 , Dr Jaideep Chakarvorty2 , Abhishek Bhardwaj 3
1,3
PG scholar, 2Head of EE Department
Baddi University Solan
Abstract: Induction motors are broadly used for the most
The increased interest in induction motors is because
reliable electric machines. They form about 80% of
of its merits over the other types of industrial motors.
electric motors and about 38% of total electric
These merits are lightness, simplicity, ruggedness,
consumption. Recently oil prices, on which electricity and
less initial cost, high torque-inertia ratio, capability of
other public utility rates are highly dependent, are rapidly
increasing. It, therefore, becomes imperative that major
attention be paid to the efficiency of induction motors.
The minimization of electrical energy consumption
much higher speed, ease of maintenance etc.
Moreover the most important feature which makes
the induction motor
most suitable alternative to dc
through better motor design becomes a major concern.
motor is its per KVA which is approximately one
This paper proposes a novel technique to improve the
fifth of that of DC motor.
performance of induction motor. By using a modified
stator winding arrangement the efficiency has been
improved by 4 to 7% and tested in laboratory.
Experimental
results
and
simulations
have
been
presented to validate the results.
Index Terms: Induction motor, Squirrel cage and
Mathematical modelling.
In the present situation induction motor consumes
large amount of electric power and increase in the
efficiency of the motor will reduce the consumption
of the electric power which in turn further reduces its
cost. [1]
There are many losses in induction motor but the
major losses are in the stator winding in terms of
I.
INTRODUCTION
stator copper loss. This paper proposes a suitable
The electric motor has a long history of development
method of reducing the stator copper loss by using
since its invention by Nicola Tesla in 1888, with
modified stator winding arrangement. It is possible
earlier effort aimed at improving power and torque
by increasing the active material part in the motor.
and reducing cost. The need for higher efficiency
Using active material such as copper effectively will
becomes apparent during the late 1970’s and by the
increase the efficiency of the motor to a considerable
early 1980’s and at least one British manufacturer
extent. The proposed motor is modelled and
had started to market a premium range of motors with
simulated with the help of SIMULINK model [2]
improved efficiency. Now the trend is towards the
design and manufacturing of motors with a small
improved efficiency at a small extra cost. It is
needless to state that this extra cost could be realized
in the savings in the operating cost. Since, efficiency
being the ratio of the amount of work produced i.e.
output power to the amount of energy consumed i.e.
input power, the Induction motor losses are the
difference between input and output powers.
Corresponding Author: Mr. Surinder Pal, PG Scholar [ M.Tech],
Department of EE, Baddi University Solan, India.
Email Id: er.surinderpal@gmail.com
The most important feature which distinguishes the
induction machine from dc machine is that the
secondary currents are created solely by induction as
in the case of transformer. The equivalent circuit is
also same as that of transformer. The rotor currents
are at a slip frequency an rotor frequency is given by
this relation f’=sf.[3]
II. EFFICIENCY IMPROVEMENT
The efficiency of the motor is increased by increasing
the active material present in the motor. This active
© 2014 PISER Journal
http://.piserjournal.org/
PISER 14, Vol.02, Issue: 04/06 July-August; Bimonthly International Journal
Page(s) 107-111
Progress In Science and Engineering Research Journal
ISSN 2347-6680 (E)
material of the motor is increased by using multi-
Actually there is some core losses in the rotor. Under
strand with multi turn coils in the stator winding.
operating conditions, however, the rotor frequency is
Two conductors separated from each other by a pole
so low that it may logically be assumed that all core
pitch from one turn. Multi strand with multi-turn
losses occur in the stator only. The efficiency of
coils will increase the area of the conductors in a slot.
induction motor is determined by loading the motor
The reduction in the stator resistance is explained as:
and measuring the input and output directly:
ƞ= Poutput/Pinput
The resistance of stator winding with single strand
with multi turn coil, R=  l Where, R=Resistance
A
of the stator winding and ρ=Resistivity of the
winding, l =Length of the winding
When in the stator winding copper as active material
is used instead of die cast aluminium and also using
the strands of multi strands with multi turns instead
Fig.1: Efficiency characteristics of induction motor
of single strands with multi turns then the resistance
is decreased and so the copper loss is decrease and
the efficiency is increases such as:
b) Power Factor of Induction Motor: When the
winding is changed from single strand with multi turn
coil into multi strands multi-turn coil the power
factor increases from 0.8 to 0.85.
Stator Copper Loss:
I²R = I 2 l
A
Resistance of the winding with multi strand with
multi-turn coil with X number of strand per turn.
R=
l
XA
Fig.2: Power factor of induction motor
Stator Copper Loss:
I²R= I 2 l ,
c) Stator Resistance
Where X= 1, 2, 3 ...N
XA
Therefore, with increase in number of strands in a
turn, the area of the coil increases, hence stator
resistance decreases to a considerable extent. (The
inductance value is same as the existing motor)
III. MEASUREMENT OF MOTOR
PARAMETERS
a) Efficiency of Induction Motor: In an induction
The resistance values in the order of few ohms and
the resistance values are crucial to determine the
winding data. Hence the resistance should be
measured with high accuracy. The stator resistance
per phase is measured by using a suitable meter.
d) No Load Test
The stator of the induction motor is energized by
applying rated voltage at rated frequency. The
corresponding input power per phase and line current
is measured accurately under no-load conditions.
motor the total losses consist of copper losses, core
losses and friction and Windage losses are occurred.
There are copper losses and core losses in the stator,
and copper losses and friction losses in the rotor.
e) Locked Rotor Test
The rotor of the induction motor is locked to keep it
at standstill and a low voltage is applied to circulate
rated stator currents. Input power per phase is
© 2014 PISER Journal
http://.piserjournal.org/
PISER 14, Vol.02, Issue: 04/06 July-August; Bimonthly International Journal
Page(s) 107-111
Progress In Science and Engineering Research Journal
ISSN 2347-6680 (E)
measured along with the input voltage and the stator
The PWM inverter is built entirely with standard
current. The slip is unity for the locked rotor
SIMULINK
condition and hence the circuit resembles that of a
controlled voltage source blocks before being applied
secondary shorted transformer.
to the asynchronous machine block’s stator windings.
blocks.
Its
output
goes
through
The machine’s rotor is short circuited. Its stator
f). Computation of Static Performance of Induction
Motor
leakage inductance is set to twice its actual value to
simulate the effect of a smoothing reactor placed
The slip is chosen in place of rotor speed as it is non
between the inverter and the machine.
dimensional and so it is applicable to any motor
frequency. Near the synchronous speed, at low slips,
The load torque applied to the machine’s shaft is kept
the torque is linear and is proportional to slip beyond
constant. The motor is started from standstill. The
the maximum torque the torque is approximately
speed set point is set to 1.0pu, or 1440 rpm. This
inversely proportional to slip.
speed is reached after 0.8s. The noise introduced by
IV. DYNAMIC SIMULATION OF
the
PWM
inverter
is
also
observed
in
the
electromagnetic torque waveform. However, the
THREE PHASE INDUCTION MOTOR
Torque and speed characteristics are obtained from
motor’s inertia prevents this noise from appearing in
the motor’s speed waveform.
this model.
a) Rotor Speed of an Induction Motor
Figure 4 & 5 shows the rotor speed curve of winding
with the single strand with multi turn coil and multi
strand with multi turn coil of the induction motor
respectively. The rotor speed is gradually increased
to the rated speed.
Fig 3: The SIMULINK block diagram of three phase induction
Fig.4: Rotor speed of existing induction motor.
motor
Table.1: Block parameters of induction motor
Quantity
Input values
No of phases
3
Number of poles
4
Frequency
50Hz
Line voltage
410 v
Stator resistance
1.9Ω
Mutual inductance
0.26674H
Above Figure shows the motor with single strand
with multi turn coil attain a steady state speed of
1440 rpm.
Fig.5: Rotor speed of new induction motor
.
A three phase motor rated 3hp, 410V, and 1440 rpm
Above Figure shows the motor with multi strand with
is fed by a sinusoidal PWM inverter. The base
multi turn coil attain a steady state speed of 1480
frequency of the sinusoidal reference wave is 50Hz.
rpm.
© 2014 PISER Journal
http://.piserjournal.org/
PISER 14, Vol.02, Issue: 04/06 July-August; Bimonthly International Journal
Page(s) 107-111
Progress In Science and Engineering Research Journal
ISSN 2347-6680 (E)
b) Time Response of Electromagnetic Torque in
Three Phase Induction Motor.
Fig.8: Existing induction motor
Above Figure shows the winding of the motor with
Fig.6: Time response of electromagnetic torque of existing
single strand with multi turn coil.
induction motor
In Fig.6. the time response of electromagnetic torque
of three-phase induction motor is expressed. The
electromagnetic torque of three-phase induction
motor is firstly variable in 0 to 0.4 second. The rated
torque is reached at 0.8 seconds.
Fig.9: New induction motor
Above Figure shows the winding of the motor with
multi strand with multi turn coil.
Fig.7: Time response of electromagnetic torque of new
induction motor.
Above Figure shows the torque of the motor with
multi strand with multi turn coil.
Table 2: Comparison of Single –Turn and Multi-Turn Motor
Existing
motor
Motor with modified
Stator winding.
Voltage
410v
410v
Frequency
50Hz
50Hz
Efficiency
80.7%
88.75%
Stator copper loss
240w
41.18w
Rotor copper loss
120w
75.3w
Fixed loss
167w
167w
Power factor
0.79
0.846
Parameters
Fig.10 Efficiency of new induction motor
Fig.11: Fig shows the torque characteristics of exiting motor.
Table 2 shows the comparison of efficiency and
losses for the existing motor and new motor. The
efficiency is increased in the new motor.
Fig.12: Fig shows the torque characteristics of new motor
© 2014 PISER Journal
http://.piserjournal.org/
PISER 14, Vol.02, Issue: 04/06 July-August; Bimonthly International Journal
Page(s) 107-111
Progress In Science and Engineering Research Journal
ISSN 2347-6680 (E)
[4]. Fernando J. T. E. Ferreira,Member, IEEE in IEEE
TRANSACTIONS ON ENERGY CONVERSION, VOL. 21,
NO. 2, JUNE 2006
[5]. A. Zabardast, and H. Mokhtari, Associated Professor
DRPT2008 6-9 April 2008 Nanjing China
[6]. Ralph Feldman, Zhang He, Matteo Tomasini, Keith Bradley,
Patrick Wheeler School of Electrical and Electronic
Engineering, The University of Nottingham Nottingham, UK.
[7].
Jia Liu1 China Institute of Atomic Energy, 102413, China
Fig.13: Fig shows the rotor & stator currents of existing
2College of Mechanical Engineering and Applied Electronics
induction motor
Technology, Beijing University of Technology, Chaoyang
District, Beijing 100124, China .
[8]. Member, IEEE Siemens Industry, Inc. 4620 Forest Ave,
Norwood, OH 45212 radu. Harry Li, PE Member, IEEE
Siemens Industry, Inc. 4620 Forest Ave, Norwood, OH
45212.
[9]. M. K. Yoon, C. S. Jeon, and S. Ken Kauh IEEE Transactions
On Energy Conversion, Vol. 17, No. 1, March 2002 Review
On 7.Efficiency Improvement In Squirrel Cage Induction
Motor By Using Dcr Technology.
[10]. Subramanian
Fig.14: Fig shows the rotor &stator current of new induction
Manoharan
Nanjundappan
Devarajan
Subbarayan M. Deivasahayam Gopalakrishnan Ranganathan
Journal of ELECTRICAL ENGINEERING, VOL. 60, NO. 4,
motor.
2009, 227–236.
V. CONCLUSION
[11]. Energy Efficient Control of Three-Phase Induction Motor -
The stator copper loss is minimized by using
A Review C. Thanga Raj, Member IACSIT, S. P. Srivastava,
modified stator winding arrangement. It is a novel
and Pramod Agarwal International Journal of Computer and
Electrical Engineering, Vol. 1, No. 1, April 2009 1793-8198.
method to increase the efficiency of three phase
A Survey of Efficiency-Estimation Methods for In-Service
squirrel cage induction motor is new. The dynamic
Induction Motors Bin Lu, Student Member, IEEE, Thomas
simulation of the motor is performed by its
G. Habetler, Fellow, IEEE, and Ronald G. Harley, Fellow,
mathematical modelling. The hardware is proposed
IEE
IEEE
TRANSACTIONS
ON
INDUSTRY
APPLICATIONS, VOL. 42, NO. 4, JULY/AUGUST 2006.
after doing the above modifications and thus the
[12]. Comparative Evaluation of Power Factor Improvement
efficiency of the motor is increased, the motor is also
Techniques for Squirrel Cage Induction Motors Rend Spde,
modelled and simulated with the help of the
Member, IEEE, and Alan K. Wallace, Senior Member, IEEE.
[13]. Effeciency improvement studies of low voltage three phase
MATLAB SIMULINK model.
squirrel-cage induction motors for general purpose.K.
Hasuike Hitachi Ltd. Narashino City, Chiba Pref., Japan
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Dec 1983.
[2]. Nyein Nyein Soe, Thet Han Yee, Soe Sandar Aung,
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power induction motor”, World academy of science,
Engineering and technology, 42-2008.
[3]. N.N.Fulton,R.D.Slaterland,
W.S.Wood,
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© 2014 PISER Journal
http://.piserjournal.org/
PISER 14, Vol.02, Issue: 04/06 July-August; Bimonthly International Journal
Page(s) 107-111