Operation of Induction Machines

1
Operation of Induction Machines

• EE 341 Energy Conversion
• Ali Keyhani
• Induction Machines
• lecture 4

2
Problem.
3 Phase Trans. 11/0.44 KV 300 KVA X0.06 P.U
Delta connected Resistive load R- 4.5 ohms
Load 1
Trans.
11 KV (infinite bus)
LV
3-phase, 8-pole 440V, 60Hz 0.08
ohm/phase 0.07ohm/phase 0.3
ohm/phase 0.1ohm/phase
m
Induction Motor (M) Rated Values
T
L
T
m
The parameters and are referred to the
stator. Assume load 1 is on when the induction
motor starts. (a) Compute the voltage on the LV
side at direct start. (b) Can this motor start a
load torque ( ) of 500 N-m? Assume load
1 is on when the motor starts. Justify your
answer.
3
HV
LV
.
J
06
1.0
Z
Z
M p,u
Load p.u
S 300 KVA
b
4
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5
(b)
R
JX
R
JX
LV
1
1
2
2
I
(I-S)
1
R
AG
S
2
6
T
500 N-m
T
s
0
S1
7
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8
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9
Induction Motor in Balanced Conditions (Stator
Ref. Frame)
4
T
Transient oscillation during startup
3
max
2
Normal operating range
Te (pu)
1
0
-1
0
0.2
0.4
0.6
0.8
1
1.2
1.4
Time (s)
10
Simulation results for free acceleration of an
induction machine using unsaturated inductances.
1
0.9
0.8
0.7
wr (pu)
0.6
0.5
0.4
0.3
0.2
0.1
0
0.2
0.4
0.6
0.8
1
1.2
1.4
Time (s)
11
EQ. CKT. of induction motor (Review)
I
R
I
1
1
2
I
exc
R
2
V
R
E
E
1
JX
1
c
2
m
N
N
1
2
IM
T
T
em
L
12
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13
R
R
JX
JX
R /s
JX
R
I
1
1
1
2
JX
2
2
1
2
2
(1-s)
R
R
JX
JX
or
c
c
m
m
s
V
V
1
1
14
R
JX
JX
R
1
2
1
2
I
I
1
2
(1-s)
R
Air Gap
V
2
s
1
Very Large (open circuit), then I is
approximately equal to zero.
Note If R X
m
exc
c
I I
1
2