The Schneider Electric A9Q41440 is an add-on residual current device from the Acti9 Vigi iC60 range, rated 40 A with 30 mA earth-leakage sensitivity, AC type, instantaneous trip, for 400-415 V AC 50/60 Hz networks. It clips onto a compatible Acti9 iC60 MCB via the plug-in connection, adding earth-fault protection without extra wiring or panel space — the combined unit occupies the same 63 mm width (7 x 9 mm pitches) as a standard 4P MCB.
The 30 mA sensitivity means it trips on ground faults as low as 30 mA, which is the standard threshold for personnel protection under IEC 61009-1 — it clears a fault before leakage reaches a dangerous level for the operator. Type AC detection covers sinusoidal AC residual currents only; if the downstream load includes rectifiers, VFDs, or switched-mode supplies that generate pulsed or DC fault current, Type A or Type B would be needed instead. The 40 A rating matches the MCB it mounts to, so the RCD and overcurrent device share the same current-carrying capacity — no derating mismatch on the outgoing circuit. Voltage-independent tripping means the RCD detects and interrupts a ground fault even if the phase voltage collapses or the neutral is lost — the trip mechanism draws its energy from the fault current itself, not from the supply. That matters for safety: a broken neutral won't leave the RCD blind.
Clip-on mounting to DIN rail — snaps onto the rail alongside the iC60 MCB, no tools needed for the mechanical fit. The plug-in electrical connection between RCD and MCB eliminates interconnecting wires; the assembly behaves as a single 4P device. Tunnel-type terminals on the bottom accept 1-35 mm² rigid or 1-25 mm² flexible cable, with a tightening torque of 3.5 N·m and a strip length of 14 mm. The bottom comb busbar compatibility allows a common neutral or phase busbar to feed multiple RCD/MCB pairs in a distribution board.