5-1. A 480-V, 60 Hz, 400-hp 0.8-PF-leading eight-pole -connected synchronous motor has a s...

5-1. A 480-V, 60 Hz, 400-hp 0.8-PF-leading eight-pole -connected synchronous motor has a synchronous reactance of 0.6 and negligible armature resistance. Ignore its friction, windage, and core losses for the purposes of this problem. Assume that |EA| is directly proportional to the field current IF (in other words, assume that the motor operates in the linear part of the magnetization curve), and that |EA| = 480 V when IF = 4 A.

(a) What is the speed of this motor?

(b) If this motor is initially supplying 400 hp at 0.8 PF lagging, what are the magnitudes and angles of 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 |EA| is increased by 30 percent, what is the new magnitude of the armature current? What is the motor's new power factor?

(e) Calculate and plot the motor's V-curve for this load condition.