The Schneider Electric A9DE3740 is an Acti9 iCV40 residual current circuit breaker with overcurrent protection (RCBO) — a 3P+N device rated 40 A with 30 mA earth-leakage sensitivity, C-curve, and a 6 kA breaking capacity at 400 V AC. It combines thermal-magnetic overcurrent protection and integrated earth-leakage protection in one DIN-rail module, saving panel space compared to separate MCB + RCCD assemblies.
The 40 A rated current (In) and C-curve (magnetic trip at 5–10 × In) make this RCBO the right choice for general-purpose distribution circuits feeding resistive and moderate inductive loads — think lighting banks, small motor groups, or socket outlets. The 30 mA earth-leakage threshold provides personal protection against indirect contact and is standard for final circuits in residential and commercial panels. The 6 kA Icn at 400 V AC meets the fault level requirement for most sub-distribution boards; if your point of coupling sees higher prospective fault current, you'll need a current-limiting upstream MCB or a higher-rated device. Thermal-magnetic trip technology means the thermal bimetal handles sustained overloads (e.g., a stalled fan drawing 50 A for minutes) while the magnetic coil trips instantaneously on short-circuit currents above 200 A (5 × 40 A).
The 18 mm phase-to-phase pitch and 9 mm phase-to-neutral pitch fit the Acti9 modular enclosure footprint. Tunnel-type terminals accept 1–16 mm² rigid or 1–10 mm² flexible cable; strip 14 mm and torque to 2 N·m. IP20 finger-safe with the enclosure closed, IP40 inside a modular enclosure — fine for clean indoor panels, not for washdown zones.