The Schneider Electric A9Y74725 is an Acti9 Vigi iCG40 add-on residual current device (RCD) — a voltage-independent, instantaneous-trip unit rated 25 A with 30 mA earth-leakage sensitivity. It clips onto the outgoing side of a compatible Acti9 MCB via screw terminals, adding ground-fault protection to a 3P+N circuit at 400 V AC. The 30 mA sensitivity covers personnel protection (hand-to-hand or hand-to-ground fault paths) per IEC 61009-2-1. Type A-SI (Super Immunised) means it rejects nuisance tripping from pulsed DC loads, variable-speed drives, and UPS systems — common in modern panels where standard Type A or AC RCDs would false-trip on leakage harmonics. Rated operational voltage is 400 V AC at 50/60 Hz, insulation voltage 440 V AC, impulse withstand 4 kV. Pollution degree 3 (conductive or dry non-conductive pollution) fits industrial control enclosures where condensation or light dust is expected.
Clip-on mounting to DIN rail, 108 mm wide (6 x 9 mm pitches), 74 mm deep, 99.5 mm tall. The neutral position is left; the device connects to the upstream MCB by screws. Tunnel terminals accept 1…16 mm² rigid or 1…10 mm² flexible, with a 14 mm strip length and 2 N·m tightening torque. IP20 on the device body, IP40 inside a modular enclosure. Ambient operating range -25…60 °C, storage -40…85 °C, with 95 % RH at 55 °C. Maximum operating altitude 2000 m. Electrical durability 10,000 cycles, mechanical 20,000 cycles.