A three phase, 25-hp, 440-V, 60-Hz, 1750 rpm, wound-rotor induction motor has the following equivalent circuit parameters:
R1=0.20 ohms, X1=1.0 ohms, R2=0.15 ohms, X2=0.8 ohms, Xm=30 ohms
The motor is connected to a three phase, 440-V, 60-Hz supply.
a) Calculate the starting torque.
b) Determine the resistance of the rheostat in the rotor circuit such that the maximum torque occurs at starting.