Cooper Bussmann FRN-R-400 Fusetron Time Delay Fuse

FRN-R-400 Fusetron Time-Delay Fuse from Bussmann (Cooper Bussmann) is a Class RK5 dual‑element cartridge fuse rated for 400 A at 250 VAC (and 250 VDC), designed to protect electrical circuits while tolerating brief startup surges from inductive loads. As a time-delay (slow‑blow) device, it helps prevent nuisance blows on short inrush currents while still delivering current‑limiting protection. It offers an interrupting rating of 200 kA at 250 VAC and 20 kA at 250 VDC, and it is non‑indicating, making it suitable for installation in standard RK5 fuse holders in industrial control panels and power distribution setups. This FRN‑R family fuse is built in a cartridge body intended for reliable, high‑current service, balancing fast protection with tolerance for brief overloads. Used in applications requiring heavy‑duty protection on 250‑V systems, the FRN-R‑400 is part of Eaton/Bussmann’s Fusetron FRN‑R line, a proven option when durable, time‑delay protection is needed for large motors, transformers, and other inductive equipment in commercial and industrial environments.