4. 6600 volt, 21000hp, Y-connected, unit power factor synchronous motor draws rated line current of 1404 amps. Synchronous reactance is 0.9 p.u. and armature resistance is 0.015 p.u. Synchronous speed is 1200 rpm.
(a) What is the rated input power of the motor?
(b) What is the internal voltage $E_a$ produced in the motor at rated conditions?
(c) What is the efficiency of the motor under full load?
(d) What is the output torque of the motor under full load?