Consider an MCC with six identical motors, each motor rated at 60 HP, three-phase, 60 Hz, 460 V, 1760 RPM, a service factor of 1.00, and a power factor of 90%. All the motors are protected by time-delay fuses and have full voltage nonreversing starter type.

(a) Estimate the efficiency of each motor if its line current is 70 A.

(b) Determine the number of poles, the slip (%), and the torque delivered (in lb-ft)

by each motor.

(c) Design a branch circuit for one motor. Assume that the motor is out of sight of both the power supply and the controller (the controller is within sight from the source). The nameplate full-load current rating of each motor is 70 A.

(d) Determine the size of the conductor, conduit, time-delay fuse, and switch for the feeder supplying the MCC.