A 500 hp, three-phase, 2200 V, 60 HZ, 12-pole, Y-connected, wound-rotor induction motor has the following parameters:
R1 = .225 ohm : R'2= .235 ohm Xeq = 1.43 ohm and Xm = 31.8 ohm and Rm = 780 ohm
Calculate the following:
(a) Slip at maximum torque
(b) Input current and power factor at maximum torque
(c) Maximum torque
(d) Resistance that must be added to the rotor windings (per phase) to achieve maximum torque at starting