A 460-V 50-hp six-pole D-connected 60-Hz three-phase induction motor has a full-load slip of 4 percent, an efficiency of 91 percent, and a power factor of 0.87 lagging. At start-up, the motor develops 1.75 times the full-load torque but draws 7 times the rated current at the rated voltage. This motor is to be started with an autotransformer reduced voltage starter.
(a) What should the output voltage of the starter circuit be to reduce the starting torque until it equals the rated torque of the motor?
(b) What will the motor starting current and the current drawn from the supply be at this voltage?