Induction Machines Performance Calculation

1
Induction Machines Performance Calculation

• EE 341 Energy Conversion
• Ali Keyhani
• Induction Machines
• lecture 3

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Induction Motor Performance Calculations
I
R
JX
JX
R
1
1
2
2
1
V
R
1
JX
c
m
Fig 1.
R
JX
R
JX
I
1
1
2
2
1
I
2
R
V
1 - s
JX
c
1
R
m
2
s
Fig 2.
3
Power crossing the air gap
Developed electromagnetic power
Rotor loss
To load
Rotational losses
4
P
P
P
P
P
P
P
(I - S)


i
g
i
g
em
o
R
1
2
2
P

P
R
P
R
I
I

Rotational losses
1
R
1
2
2
Fig. 3
R
JX
R
JX
I
1
1
2
2
1
1 - s
R
2
s
Fig. 4
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Induction Generator
I
a
N
T
I
m
b
S
N
T
T
m
ext
I
S
c
T
ext
Stator wind direction
2-p induction generator
I
s
Fig. 5
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For induction generators
1.) that is mechanical power
supplied by the prime mover.
2.) and are rotating in the
same direction.
3.) Generator action Electrical power is
supplied to the network via stator terminals.
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Stand Still Condition
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7.1 example ind - 1
N
750 RPM
m
N
Syn gen
Ind. machine
m
P6
P4
f
?
r
A six pole induction motor is supplied by a
synchronous generator having four poles and
running at 1500 RPM. If the speed of the
induction motor is 750 RPM, what is the rotor
frequency?
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Solution
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7-7 example ind-2
JX
R
I
JX
2
I
1
1
2
1
R
2
s
P
P
3KW
Air gap
ag
In rotor
N
1000RPM
P4
60HZ
P
m
Rotor loss
The input to the rotor circuit of a four pole
60HZ induction motor, running at 1000RPM, is 3kW.
What is the rotor copper loss?
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Solution
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7-8 Example ind-3
I
60A
R
JX
R
s
JX

I
1
1
2
2
1
R
(I-S)
I
c
2
R
V
JX
c
1
s
m
400
n
m
s.06
P
0
The stator current of a 400V, 3-Phase, Wye -
connected, four pole, 60Hz induction motor
running at s0.06 is 60A at P.F .866. The
stator copper loss is 2700W, the total iron and
rotational losses are 3600W. Calculate the
efficiency of the motor.
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Solution