Bussmann FRN-R-400 Fusetron Time Delay Current Limiting Fuse

The Bussmann Fusetron FRN-R-400 is a dual-element, time-delay current-limiting fuse with a cartridge body, designed for Class RK5 protection in high-current distribution settings and motor circuits, rated at 400 A. It operates on 250 VAC or 250 VDC and delivers a 200 kA interrupt rating at AC and 20 kA at DC, providing fast fault clearance while tolerating brief startup surges common with inductive loads. The FRN-R-400 is approximately 8.63 inches long and belongs to Bussmann’s RK5 family of fuses used for main feeders and other demanding applications requiring reliable time-delay protection. Typical uses include protection of power distribution feeds and motor-driven equipment where coordination with upstream protections is essential.