The Schneider Electric A9R05491 is a 4-pole residual current circuit breaker (RCCB) from the Acti9 iID series, rated for 100 A continuous current and 300 mA earth-leakage sensitivity. The selective (time-delay) characteristic means it holds during short transient earth faults, letting downstream RCCBs trip first; you use it at the distribution board incomer or feeder to maintain coordination.
Rated operational voltage is 380...415 V AC 50/60 Hz, so it fits standard three-phase four-wire networks (230/400 V or 240/415 V) across Europe and much of Asia. The 100 A frame covers main switchboard incomers or heavy feeder circuits up to that load. Breaking capacity is Idm 1500 A and Im 1500 A — this is the short-circuit breaking capacity of the RCCB itself. In a typical installation, the upstream MCB or fuse provides the fault-clearing; the RCCB must be rated to withstand the let-through energy. The device is voltage-independent for residual current tripping — it does not need a separate power supply to detect earth leakage and open the contacts. This is a reliability advantage: the RCCB trips even if the neutral is lost or the supply voltage drops. The 8/20 µs impulse withstand of 3000 A per EN/IEC 61008-1 means it survives surge currents from lightning or switching without nuisance tripping.
Neutral is on the left, which matters when wiring a pre-assembled distribution board — verify the busbar orientation. Wire stripping length is 14 mm. IP20 on the device body, IP40 inside a modular enclosure — standard for panel mounting, not for wet-area exposure.