A motor control center has three induction motors each rated at 40 HP and 480 V and 4 induction motors each rated at 30 HP and 480-V. Each 40-HP motor has an efficiency of 0.92, 1172 rpm, a power factor of 0.85, a nameplate rating of 45 A, a service factor of 1.15, and a FVNR controller. Each 30-HP motor has an efficiency of 0.90, a power factor of 0.90 , and an FVR controller.

(a) Size the conductor (THW, Cu), the fuse, and the overload protection of each 40-HP motor if a time-delay fuse is used. Assume that all the motors are within sight of both the fuse and the controller.

(b) Design and show the layout of the motor control center.

(c) Determine the induction motors (by specifying their HP and their number) that needs to be replaced with synchronous motors so that the overall power factor of the MCC is as close to unity as possible without changing the total kW load of the MCC nor the HP ratings of the motors. Assume that the power factor for any synchronous motor is 0.90 leading.