ECE4501 Power Systems UMD Spring 2003

QUIZ 6:

A 6-pole, 2200 Volt, 50 HP three-phase squirrel-cage induction motor is rated for 60 Hz operation and has the following constants:

R1 = 3.5 Ohms, R2 = 2.4 Ohms, X1 = X2 = 7.2 Ohms, Xm = 328 Ohms, Rotational Losses = 1% on machine base

If the motor is energized at 2400 Volts and turns a dynamic load at 1176 RPM, find the following using the approximate equivalent circuit as needed:

a) Slip, S

b) Starting Current, I_ST

c) Load Current

d) Shaft Horsepower

e) Shaft Torque

f) Efficiency of the motor