A 480-V, 60Hz, 500-hp 0.85-PF-leading eight-pole delta-connected synchronous motor has a synchronous reactance of 0.6 ohms and neglible armature resistance. Ignore its friction, windage and core losses for the purposes of this problem. |Ea| = 480 V when Field Current = 4 A (Assume that |Ea| is directly proportional to the field current).
a.) What is the speed of this motor?
b.) If this motor is initially supplying 500 hp at 0.85 PF lagging, what are Ea and Ia?
c.) How much torque is this motor producing? What is the torque angle? How near is this value to the maximum possible induced torque of the motor for this field current setting?
d.) If field current is increased by 20 percent, what is the new magnitude of the armature current? What is the motor's new power factor