From a three-phase, 60-Hz system, through a motor-generator set consisting of two directly coupled synchronous machines, electric power is supplied to a three-phase, 50-Hz system.
(a) Determine the minimum number of poles for the motor.
(b) Determine the minimum number of poles for the generator.
(c) With the number of poles decided, find the speed in r/min at which the motor-generator set will operate.