The A9Y75640 is a voltage-independent add-on residual current device (RCD) from the Acti9 Vigi iCG40 series, designed to clip onto the outgoing side of a compatible Acti9 MCB. It provides earth-leakage protection for a single-phase 230 V AC circuit at 40 A rated current, with a 300 mA sensitivity. The Type A-SI (Super Immunised) classification means it handles pulsed DC fault currents and resists nuisance tripping from high-frequency harmonics or transient surges common on modern electronic loads — think variable-speed drives, UPS systems, or LED lighting banks where standard Type A or AC RCDs can false-trip. The instantaneous response (no intentional time delay) suits it as a group incomer protecting a sub-distribution board rather than individual final circuits. The 40 A rating matches the upstream MCB capacity, so coordination is straightforward: the RCD and MCB share the same current rating, and the voltage-independent trip mechanism means the RCD operates even if the neutral is lost — a safety-relevant detail for group incomer duty. The 300 mA sensitivity is deliberately less sensitive than 30 mA; it is sized for equipment protection and fire prevention rather than personal shock protection, which is why it sits at the group incomer position per the device location spec.
The tunnel-type terminals accept 1 to 16 mm² rigid or 1 to 10 mm² flexible conductors on top; wire stripping length is 14 mm. The electrical connection to the MCB is via screws, so the RCD is mechanically ganged to the breaker — no extra busbar required. IP20 for the terminals, IP40 for the modular enclosure inside a panel. Ambient operating range -25 to 60 °C, storage -40 to 85 °C, with 95% relative humidity at 55 °C and operating altitude up to 2000 m.