What this 1 A D-curve MCB is for
The Schneider Electric A9F45401 is a 4-pole Acti9 iC60N miniature circuit breaker rated at 1 A with a D tripping curve. The D curve's magnetic trip threshold of 12 x In (±20 %) means it takes a sustained 12 A fault to trigger the instantaneous magnetic release; below that, the thermal-magnetic trip handles overloads. That 1 A rating makes it a fit for control transformers, relay coils, or PLC power supplies pulling under an amp per phase. The 4-pole version protects all four conductors in a three-phase-plus-neutral circuit. At 72 mm wide, it takes up eight 9 mm pitch modules on the rail, so plan your enclosure fill factor accordingly.
Breaking capacity and dual-standard rating
This breaker carries dual certification to EN/IEC 60898-1 (the household-and-similar MCB standard) and EN/IEC 60947-2 (the industrial circuit-breaker standard). That matters for panel builders who need one part number that satisfies both a residential-style distribution board and an industrial switchboard. The industrial rating gives a 50 kA Icu at 220...240 V AC and 380...415 V AC, dropping to 25 kA at 440 V AC. For most motor-control panels fed from a 400 V transformer, the 50 kA Icu is the number that governs the upstream fault level. Overvoltage category IV covers the main incoming supply side, so it's suitable as a service-entrance or main-distribution breaker, not just downstream sub-feed.
The connection is a single terminal per pole (top and bottom), so you land one conductor per side — no looping through the breaker. The toggle control with trip indicator gives local visual confirmation of the tripped state.
Environmental and durability ratings
IP20 finger protection per IEC 60529 — fine for enclosed panels, not for wet locations. Padlockable for lockout/tagout procedures.