The Schneider Electric A9N19857 is an Acti9 C120L miniature circuit breaker (MCB) with 2 poles, rated 125 A at 30 °C, C curve, and a breaking capacity of 15 kA Icn / Icu at 400 V AC 50/60 Hz.
The 125 A rated current at 30 °C determines the maximum continuous load this MCB can carry without tripping. That rating holds under both IEC 60898-1 (Icn) and IEC 60947-2 (Icu) standards, so it is accepted for both household and industrial panel designs. The thermal-magnetic trip unit combines a bimetal strip for overload protection and a solenoid for short-circuit protection. With 2 protected poles, it disconnects both line conductors on a fault — required for single-phase 230 V or split-phase 400 V circuits where both poles carry current.
Deployment context
The tunnel-type terminals accept up to 50 mm² rigid or 35 mm² flexible conductors, with a tightening torque of 3.5 N·m — typical for a 125 A feeder breaker feeding a sub-distribution board or a large load.