resulting error in the
prototype construction and testing
.
This paper demonstrates the
simulation of steady state performance of induction motor by
MATLAB Program Three phase 3 hp induction motor is modeled
and simulated with SIMULINK model.

Keywords
Squirrel cage

induction motor, modeling and
simulation, MATLAB software, torque, speed.

I. I
NTRODUCTION

N induction motor is simply an electric transformer
whose magnetic circuit is separated by an air gap into two
relatively movable portions, one carrying the primary and the
other the secondary winding. Alternating current supplied to
the primary winding from an electric power system induces an
opposing current in the secondary winding, when the latter is
short circuited or closed through external impedance. Relative
motion between the primary and secondary structure is
produced by the electromagnetic forces corresponding to the
power thus transferred across the air gap by induction.
The essential features which distinguish the induction
machine from other type of electric motors is that the
secondary currents are created solely by induction, as in a
transformer instead of being supplied by a dc exciter or other
external power sources, as in synchronous and dc machines.
The equivalent circuit of the induction motor is very similar
to that for a transformer. Although the rotor currents are at slip
frequency, the rotor is incorporated into the circuit in sample
way. Three phase induction motor is the most commonly used
motor in industrial application for its simple design, reliable
operation, rugged construction, low initial cost, easy operation
and simple maintenance, high efficiency and having sample


Nyein Nyein Soe is with the Electrical Power Engineering Department,
Mandalay Technological University, Mandalay, Myanmar (corresponding
author to provide phone: 095 067 22123; e mail: nyeinnsoe@ gmail.com,
nyeintzaw@gmail.com).
Thet Thet Han Yee is with the Electrical Power Engineering Department,
Mandalay
Technological
University,
Mandalay,
Myanmar
(e mail:
thetthethanyee@gmail.com).
Soe Sandar Aung is with the Electrical Power Engineering Department,
Mandalay
Technological
University,
Mandalay,
Myanmar
(e mail:
soesandarag@gmail.com).
control gear for starting and speed control. Induction motors
are available with torque characteristics suitable for a wide
variety of applications. Moreover, squirrel cage induction
motors have more advantages than wound type. Squirrel cage
induction motors have higher efficiency, less maintenances,
better space factor in slots and lower cost. [1]

Fig. 1 Elementary equivalent circuit for induction motor

II. M
EASUREMENT OF
M
OTOR
P
ARAMETERS

A. Stator Resistance
With the rotor at standstill, the stator phase resistance is
measured by applying a dc voltage and the resulting current.
While this procedure gives only the dc resistance at a certain
temperature, the ac resistance has to be calculated by
considering the wire size, the stator frequency and the
operating temperature.
B. No-load Test
The induction motor is driven at synchronous speed by
another motor, preferably a dc motor. Then the stator is
energized by applying rated voltage at rated frequency. The
input power per phase is measured.
C. Locked-Rotor Test
The rotor of the induction motor is locked to keep it at
standstill and a set of low three phase voltages is applied to
calculate rated stator currents. The input power per phase is
measured along with the input voltage and stator current. The
slip is unity for the locked rotor condition and hence the
circuit resembles that of a secondary shorted transformer. [2]
III. S
TEADY
S
TATE
P
ERFORMANCE
C
ALCULATION OF
I
NDUCTION
M
OTOR

The required parameters for steady state performance
calculation of induction motor are received from laboratory
Dynamic Modeling and Simulation of Three
phase Small Power Induction Motor
Nyein Nyein Soe, Thet Thet Han Yee, and Soe Sandar Aung
A
PROCEEDINGS OF WORLD ACADEMY OF SCIENCE, ENGINEERING AND TECHNOLOGY VOLUME 32 AUGUST 2008 ISSN 2070-3740
PWASET VOLUME 32 AUGUST 2008 ISSN 2070-3740
451
© 2008 WASET.ORG

test results. Torque speed characteristic, power speed
characteristic, efficiency speed characteristic of induction
motor and magnitude of rotor and stator currents are shown in
this paper.

TABLE

I
I
NPUT
P
ARAMETERS OF
I
NDUCTION
M
OTOR

Symbol
Quantity
Input values

phase
3
p
Number of pole
4

f
frequency

50Hz
vll
Line to line voltage
380V
Rs
Stator resistance
3.5


Rr
Rotor resistance
3.16

Rc
Resistance to account
for core losses
701


Xm
Magnetizing reactance
83.8


Xls
Stator magnetizing
leakage reactance
2.17


Xlr

Rotor magnetizing
leakage reactance
2.14





A. Torque Speed Characteristic of Induction Motor
Full load torque,
2
2
2
2
r
r
r
r
s
f
X
s
R
E
R
k
T
+
=
(1)
Maximum torque,
r
m
X
kE
T
2
2
2
=
(2)
where, s= full load slip of motor



Fig. 2 Torque slip characteristic of induction motor
B. Power Speed Characteristic of Induction Motor

Power=
m
T (3)
where, rotor speed
m
=
2
p
r =
(
)
2
1
p
s
s
(4)


Fig. 3 Power slip characteristic of induction motor

C. Magnitude of Stator Current in Induction Motor



Fig. 4 Stator Current Vs slip characteristic of induction motor

D. Efficiency of Induction Motor
In an induction motor, 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
frictional losses in the rotor. Actually there is some core losses
in the rotor. Under operating conditions, however, the rotor
frequency is so low that it may logically be assumed that all
core losses occur in the stator only. The efficiency of induction
motor can be determined by loading the motor and measuring
the input and output directly.
= P
output
/P
input














(5)
PROCEEDINGS OF WORLD ACADEMY OF SCIENCE, ENGINEERING AND TECHNOLOGY VOLUME 32 AUGUST 2008 ISSN 2070-3740
PWASET VOLUME 32 AUGUST 2008 ISSN 2070-3740
452
© 2008 WASET.ORG



Fig. 5 Efficiency speed characteristic of induction motor

E. Magnitude of Rotor Current in Induction Motor



Fig. 6 Rotor Current Vs speed characteristic of induction motor

IV. C
OMPUTATION OF
S
TEADY
S
TATE
P
ERFORMANCE OF
I
NDUCTION
M
OTOR

The slip is chosen in place of rotor speed because it is
nondimensional and so it is applicable to any motor frequency.
Near the synchronous speed, at low slips, the torque is linear
and is proportional to slip; beyond the maximum torque, the
torque is approximately inversely proportional to slip. [3]
A flow chart for the evaluation of the steady state
performance of the motor is shown in Fig. 7. The torque Vs
slip characteristics are shown from point 1 to 1.
The maximum torque for induction motor is 0.2 slip
position as shown in Fig. 2. The lowest value of torque is
occurred at 0.2 slip point.
V. D
YNAMIC
S
IMULATION OF
T
HREE
P
HASE
I
NDUCTION
M
OTOR

The dynamic model of induction machine is built by
SIMULINK model. Torque, speed, stator and rotor current are
obtained from this model.


Fig.7 The SIMULINK block diagram of three phase induction
motor

TABLE

II
B
LOCK
P
ARAMETERS OF
I
NDUCTION
M
OTOR

Required Parameter
values
phase
3
Number of pole
4

frequency

50Hz
Line to line voltage
380V
Stator resistance
3.5


Rotor resistance
3.16

Resistance to account for
core losses
701


Mutual inductance
0.26674H
Stator magnetizing
leakage inductance
6.90732mH
Rotor magnetizing
leakage inductance
6.81183mH



A three phase motor rated 3 hp, 380 V, 1425 rpm is fed by a
sinusoidal PWM inverter. The base frequency of the sinusoidal
reference wave is 50 Hz The PWM inverter is built entirely
with standard Simulink blocks. Its output goes through
Controlled Voltage Source blocks before being applied to the
Asynchronous Machine block's stator windings. The machine's
rotor is short circuited. Its stator leakage inductance L
ls
is set
to twice its actual value to simulate the effect of a smoothing
reactor placed between the inverter and the machine. The load
torque applied to the machine's shaft is constant and set to its
nominal value of 11.9 N.m.
The motor is started from stall. The speed setpoint is set to
1.0 pu, or 1425 rpm. This speed is reached after 0.8 s.
The noise introduced by the PWM inverter is also observed
in the electromagnetic torque waveform T
e
. However, the
PROCEEDINGS OF WORLD ACADEMY OF SCIENCE, ENGINEERING AND TECHNOLOGY VOLUME 32 AUGUST 2008 ISSN 2070-3740
PWASET VOLUME 32 AUGUST 2008 ISSN 2070-3740
453
© 2008 WASET.ORG

motor's inertia prevents this noise from appearing in the
motor's speed waveform.
VI. R
OTOR
S
PEED OF AN
I
NDUCTION
M
OTOR

Fig. 8 shows the rotor speed curve of three ph