A 75 kW, 440 V, 3-phase, 6-pole, 50 Hz, wound-rotor induction motor has a full- load slip of 0.04 and the slip at maximum torque of 0.2 when operating at rated voltage and frequency with rotor winding short-circuited at the slip-rings. As sume the stator resistance and rotational losses to be negligible. Find:
(a) maximum torque,
(b) starting torque, and
(c) full-load rotor copper-loss. The rotor resistance is now doubled by adding an external series resistance. Determine:
(d) slip at full-load,
(e) full-load torque, and
(f ) slip at maximum torque.