PE Power Sample Problem 3

Calculate the maximum rating of a non-time-delay fuse for overcurrent protection of a feeder supplying a group of four 3-phase, 575V, synchronous-type unity power factor motors with following horsepower ratings (assume 75⁰C rated terminals) as per NEC® 2017. These motors will be protected by a dedicated branch-circuit overcurrent protection device in the form of a non-time-delay fuse. MotorA= 25 hp, MotorB= 30 hp, MotorC= 40 hp, MotorD= 50 hp.
(A) 200A
(B) 225A
(C) 250A
(D) 300A

Wasim Asghar – P.E, P.ENG, M.ENG

Licensed Professional Engineer in Texas (PE), Florida (PE) and Ontario (P. Eng) with consulting experience in design, commissioning and plant engineering for clients in Energy, Mining and Infrastructure.