The Schneider Electric C125N45AFM is a ComPacT NS new generation molded case circuit breaker (MCCB) rated 1250 A at 50 °C, in a 4-pole (4P) fixed-mount configuration with a MicroLogic 5.0 A electronic trip unit. It's built for distribution duty per EN/IEC 60947-2, meaning it protects feeders and main switchboards in commercial and industrial power systems — the kind of install where you need selectivity and coordination downstream, not just a simple branch breaker. Breaking capacity is the headline here: 85 kA Icu at 240 V AC, 50 kA at 415 V, 40 kA at 525 V, and 30 kA at 690 V.
That S function is what separates a distribution breaker from a simple thermal-magnetic — it lets you coordinate with downstream breakers so only the faulted branch clears, not the whole board. The thermal memory holds for 20 minutes, which matters if you're resetting after a hot overload on a motor feeder. The trip unit includes an ammeter (type of measurement: ammeter) and an LCD display for reading load current locally. Four red LEDs flag fault types; one yellow LED indicates an overload condition. That's useful for an electrician walking the board — they can see at a glance whether the trip was overload or short-circuit without hooking up a laptop.
Fixed mounting on a backplate, 280 mm wide by 327 mm tall by 147 mm deep. Connection pitch is 70 mm, and both upside and downside connections are front-facing — that means you can land cables without needing rear access, which is standard for most switchboards but worth confirming if you're retrofitting into a tight enclosure. Manually operated (no motor operator included), with the neutral on the left side of the 4-pole block. Mechanical durability is 10,000 cycles; electrical durability ranges from 2,000 cycles at full-rated 690 V to 5,000 cycles at half-rated 440 V. That's typical for a fixed-mount distribution breaker — it's not designed for frequent switching like a contactor, but it handles routine isolation and infrequent fault clearing without issue.
The ComPacT NS new generation family is widely stocked, but a 1250 A frame is a larger unit — lead time can vary with demand, so a firm RFQ is the right next step if you're planning a board build.