Gould Shawmut TR400R TriOnic dual-element time-delay fuse, RK5 series, rated 400 A at 250 V.
It is a time-delay (slow-blow) device designed to tolerate brief inrush currents while protecting circuits from sustained overcurrent conditions.
The TR400R uses Gould Shawmut's TriOnic dual-element construction, a hallmark of the RK5 family, to deliver reliable performance at high-current levels.
