The A9DE7740 is a 40 A residual current circuit breaker with overcurrent protection (RCBO) from the Acti9 iCV40 series, combining a C-curve MCB and a 300 mA earth-leakage module in a single 4-module (72 mm) wide package. The 40 A rated current and C-curve magnetic trip of 5 to 10 times In mean it handles general-purpose loads like lighting, socket circuits, and small distribution boards where moderate inrush from motors or transformers is expected. The integrated earth-leakage protection is fixed at 300 mA sensitivity, which is a common threshold for fire protection rather than personnel protection (30 mA is typical for shock risk). This makes the unit suitable for outgoing circuits where the priority is detecting insulation degradation or arcing faults before they cause a fire, such as in distribution boards feeding multiple socket outlets or fixed equipment. The thermal-magnetic trip unit provides both overload (thermal bimetal) and short-circuit (magnetic solenoid) response in one device.
Clip-on mounting to DIN rail with a 9 mm pitch between phase and neutral. The 3P+N configuration with neutral on the left is standard for three-phase outgoing feeders. Tunnel terminals accept 1 to 16 mm² rigid or 1 to 10 mm² flexible; strip length 14 mm, torque to 2 N·m. IP20 rated for enclosure use — not for wet or outdoor locations without a weatherproof cabinet.