The ABB XT5NU340ABNF000XXX is a 3-pole molded case circuit breaker from the XT5N series, rated for 400 A continuous current at 690 VAC. It carries a TMA 400-4000 thermal-magnetic trip unit with adjustable overload and fixed instantaneous settings, suited for protecting feeders and large motor branch circuits in industrial switchboards.
The 400 A rating at 690 VAC defines the breaker's continuous current capacity at its maximum rated voltage. For a 480 VAC panel, the same 400 A frame carries full ampacity without derating. The 3-pole configuration matches three-phase distribution; the TMA trip unit provides thermal protection for overloads and magnetic pickup for short circuits, with the 400-4000 range indicating the adjustable thermal element covers 400 A to 4000 A (the frame's upper limit).
Panel integration
The XT5N frame mounts in standard switchboard or panelboard cubicles with bolted connections. Line and load lugs accept copper or aluminum conductors sized for 400 A. The TMA trip unit's dials are accessible through the cover for field adjustment of the thermal pickup without removing the breaker.