A4J400 – GOULD 400A 600V FAST ACTING FUSE

The Gould A4J400 is a fast-acting (non-time-delay) Class J fuse, meaning it will open very quickly on both overloads and short circuits. Time-delay Class J fuses (such as the AJT series) can ride through brief motor-start inrush currents without blowing. If you are protecting a motor or transformer load that draws high inrush current, a time-delay Class J fuse is generally preferred. For purely resistive or capacitor/semiconductor loads where fast response is critical, the A4J400 is the correct choice.

Yes — Gould and Shawmut are the same product lineage (Gould acquired Shawmut, which later became Ferraz Shawmut / Mersen). The A4J400 catalogue number remained consistent across these brand transitions, so the current production equivalent is a direct drop-in replacement for any previously installed Gould or Shawmut A4J400 in the same Class J holder.

The A4J400's 200kA interrupting rating (IR) meets and exceeds the available fault current at the vast majority of Canadian industrial distribution points, and satisfies the requirements of the Canadian Electrical Code (CEC) for equipment protection at 600V. Always verify the available fault current (AFC) at the point of installation with your electrical engineer or utility — the fuse's IR must equal or exceed the AFC at that location.