Schneider Electric A9KR12240BQ is an Acti9 ID K residual current circuit breaker (RCCB) — a 2-pole, 40 A device with 100 mA earth-leakage sensitivity, Type AC, rated for 220...240 V AC at 50 Hz. The 100 mA sensitivity is the deciding spec for this RCCB: it's sized for group incomer duty where you need earth-fault protection but want to avoid nuisance tripping from normal leakage on a multi-circuit distribution board.
The 40 A rated current (In) governs the continuous load it can carry — match it to the upstream MCB rating or the distribution board's design current. The 100 mA sensitivity is the trip threshold for earth leakage; it's higher than the 30 mA used for personal shock protection, so this RCCB is intended for equipment and fire protection on a group supply, not for socket-outlet circuits where 30 mA is standard. The voltage-independent residual current tripping technology means it doesn't need an auxiliary supply to detect leakage and trip — it works even if the neutral is lost upstream.
The IP20 body is fine for enclosed distribution boards; the IP40 modular enclosure rating applies when installed in a Schneider-branded enclosure. Pollution degree 2 means it's rated for normal indoor environments with only non-conductive contamination.
Certified to IS 12640-1, EN/IEC 61008-1, and EN/IEC 61008-2-1 — the harmonised standards for residual current operated circuit-breakers without integral overcurrent protection. The 8/20 µs impulse withstand rating of 200 A per EN/IEC 61008-1 means it survives surge currents from lightning or switching transients without nuisance tripping. Storage temperature range is -25...85 °C; relative humidity tolerance is 95 % at 55 °C.