The Schneider Electric A9N18344 is an Acti9 C120N miniature circuit breaker rated 63 A at 30 °C, B curve, 2-pole, with a 10 kA Icn breaking capacity at 400 V AC per EN/IEC 60898-1. It also carries a 6 kA Icu rating at 440 V AC and 10 kA Icu at 380–415 V AC per EN/IEC 60947-2, which governs its use in industrial distribution panels where the higher fault-current headroom matters.
The B curve means the magnetic trip fires between 3 and 5 times In — so for a 63 A breaker, instantaneous trip starts around 189 A and is guaranteed by 315 A. The 60947-2 rating of 10 kA Icu at 380–415 V AC gives you the fault-clearing confidence for a 400 V distribution board feeding downstream sub-circuits. Thermal-magnetic trip technology means it uses a bimetal strip for overload protection and a solenoid for short-circuit — no electronics to fail, no auxiliary power needed. The 63 A rating at 30 °C is the baseline; expect derating at higher ambient temperatures inside a crowded enclosure.
The tunnel-type terminals accept 1–50 mm² rigid or 1.5–35 mm² flexible cable; strip 15 mm and torque to 3.5 N·m. Neutral is on the left, poles are protected, and the toggle gives clear ON/OFF indication. IP20 finger-safe front, so it lives inside an enclosure — not in a washdown zone.