Page 181 - Solutions Manual to accompany Electric Machinery Fundamentals

This machine is rated at 75 kW. It produces an output power of 75 kW at 3.1% slip, or a speed of 2907
r/min.
6-19. A dc test is performed on a 460-V -connected 100-hp induction motor. If V DC = 21 V and I DC = 72 A,
what is the stator resistance R 1 ? Why is this so?

SOLUTION If this motor’s armature is connected in delta, then there will be two phases in parallel with one
phase between the lines tested.

V R R
DC 1 1

R 1

Therefore, the stator resistance R 1 will be


V DC  RR  R 1   2 R
1
1
I DC R  1  1 R 1 R  3 1
3 V 3 21 V 

R  DC     0.438 
1

2 I DC 2 72 A 
6-20. A 208-V six-pole Y-connected 25-hp design class B induction motor is tested in the laboratory, with the
following results:
No load: 208 V, 24.0 A, 1400 W, 60 Hz
Locked rotor: 24.6 V, 64.5 A, 2200 W, 15 Hz

Dc test: 13.5 V, 64 A
Find the equivalent circuit of this motor, and plot its torque-speed characteristic curve.

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