What this 250 A breaker brings to the panel
The C40N42D250 is a ComPacT NSX400N frame circuit breaker from Schneider Electric, rated 250 A at 40 °C with a MicroLogic 2.3 electronic trip unit. It's a 4-pole (4P) device built to EN/IEC 60947-2, with a breaking capacity code of N — 50 kA Icu at 415 V AC. That N rating means it handles the high fault currents common in industrial distribution panels without cascading upstream, so you don't oversize the main breaker just to protect a feeder.
Trip unit and protection: what the MicroLogic 2.3 actually does
The MicroLogic 2.3 provides three protection functions: L for overload (long-time), So for short-time short-circuit with a fixed delay, and I for instantaneous short-circuit. That fixed-delay So is the key differentiator — it lets you coordinate downstream breakers without nuisance tripping on transient faults. That's a real help on motor-starting circuits where repeated overloads can cook the cable before the bimetal catches up.
This breaker delivers 85 kA Icu at 240 V AC, 50 kA at 415 V, 42 kA at 440 V, 30 kA at 500 V, 22 kA at 525 V, and 10 kA at 690 V — all per IEC 60947-2. The UL ratings track similarly: 85 kA at 240 V, 50 kA at 480 V, and 20 kA at 600 V per UL 60947-4-1.
Mounting and integration in the panel
Dimensions are 255 mm high, 185 mm wide, 110 mm deep. IK07 impact rating means it survives a dropped tool without cracking the housing.