The Schneider Electric C125H35EFM is a ComPacT NS new generation molded case circuit breaker, part of the NS630b...1600 range, rated 1250 A at 50 °C with a MicroLogic 5.0 E electronic trip unit. The 85 kA Icu at 220/240 V AC (70 kA at 380/415 V, 65 kA at 440 V, 50 kA at 500/525 V, 42 kA at 660/690 V) per IEC 60947-2 tells you the maximum fault current this breaker can safely interrupt without welding its contacts — critical for selectivity studies and SCCR compliance in a distribution panel. The 1250 A frame means it handles main feeder or large motor circuit duty where the load current stays under that threshold at 50 °C ambient. The MicroLogic 5.0 E trip unit provides L (long-time overload), S (short-time short-circuit), and I (instantaneous) protection curves, plus energy metering — so you get both trip coordination and consumption data from one device. The electronic trip gives adjustable settings, unlike fixed thermal-magnetic units, which matters when you need to fine-tune selectivity with downstream breakers. Fixed mounting on a backplate with front connections top and bottom, 70 mm connection pitch. The 3P (three-pole) configuration suits three-phase AC distribution networks at 50/60 Hz. IP40 enclosure protection keeps out tools and small debris; IK07 impact rating handles incidental knocks during installation.
Power losses are 44 W at rated current — useful for thermal management inside a sealed enclosure. The 20-minute thermal memory in the MicroLogic 5.0 E means the trip unit remembers prior heating after a fault, so it doesn't reset too soon on a hot breaker. Electrical durability is 2000 cycles at 690 V In, 3000 at In/2; mechanical durability is 10,000 cycles. That's typical for a distribution-class MCCB — not a switching device, but fine for infrequent manual operations and fault clearing. Altitude derating applies above 2000 m — up to 5000 m with derating. Relative humidity range is 0-95%. Overvoltage category III, utilization category B. These are standard for main distribution boards in commercial and industrial buildings.
This MCCB mounts fixed to a backplate — no DIN rail, no draw-out cradle. The 327 mm height, 210 mm width, and 147 mm depth mean it needs a dedicated compartment in the switchboard, not a crowded sub-panel. The LCD display on the MicroLogic 5.0 E shows real-time current, energy, and trip data — useful for commissioning and troubleshooting without a separate meter. Four red LEDs for fault indication and one yellow LED for overload give immediate visual status. Manually operated — no motor operator or shunt trip included, though those can be added as accessories. The 44 W heat dissipation should be factored into the enclosure cooling calculation, especially if multiple breakers are ganged.