The Schneider Electric A9N18393 is an Acti9 C120N miniature circuit breaker rated 125 A at 30 °C, 4-pole, with a D curve that trips magnetically at 10...14 × In. That magnetic threshold means it holds through high inrush from motor starts or transformer energization — the D curve is the one you spec when the load isn't purely resistive and you need the branch to stay closed during the first few cycles. Breaking capacity is 10 kA Icn at 400 V AC per EN/IEC 60898-1, and 6 kA Icu at 440 V AC per EN/IEC 60947-2. At 220...240 V AC the Icu jumps to 20 kA, and at 380...415 V AC it holds 10 kA Icu. That dual-standard rating means the same breaker fits both residential (60898-1) and industrial (60947-2) coordination studies — the 60947-2 numbers are what a panel builder uses for SCCR on the nameplate.
DIN rail and panel fit
The breaker takes 12 × 9 mm pitch modules — 108 mm wide — so it fills a standard 12-module slot in a distribution board. Tunnel terminals accept 1...50 mm² rigid or 1.5...35 mm² flexible, with a 3.5 N·m tightening torque and 15 mm strip length. That wire range covers the 125 A feed with 25 or 35 mm² tails without needing a reducer lug.