5-13. A 480-V 100-kW 0.8-PF leading 50-Hz four-pole Y-connected synchronous motor has a sy...

5-13. A 480-V 100-kW 0.8-PF leading 50-Hz four-pole Y-connected synchronous motor has a synchronous reactance of and a negligible armature resistance. The rotational losses are also to be ignored. This motor is to be operated over a continuous range of speeds from 300 to 1500 r/min, where the speed changes are to be accomplished by controlling the system frequency with a solid-state drive.

(a) Over what range must the input frequency be varied to provide this speed control range?

(b) How large is EA at the motor’s rated conditions?

(c) What is the maximum power the motor can produce at rated speed with the EA calculated in part (b)?

(d) What is the largest value that EA could be at 300 r/min?

(e) Assuming that the applied voltage is derated by the same amount as EA, what is the maximum power the motor could supply at 300 r/min?

(f) How does the power capability of a synchronous motor relate to its speed?