The Schneider Electric Acti9 iID A9R91440 is a 4-pole residual current circuit breaker (RCCB) rated at 40 A with 30 mA earth-leakage sensitivity. The 73.5 mm depth fits standard modular enclosures.
Type A-SI: what it means on the line
This RCCB carries Type A-SI (Super Immunised) earth-leakage protection. That means it handles pulsed DC residual currents (Type A capability) plus high-frequency leakage from VFDs, UPSs, or switching power supplies without nuisance tripping. The SI suffix — Super Immunised — gives it a higher immunity to transient surges and high-frequency noise than a standard Type A. For a line with variable-speed drives or electronic loads, this is the difference between a stable circuit and a callout at 2 AM for a false trip. It is voltage independent — the tripping mechanism stores enough energy from the fault current itself to open the contacts, so it works even if the supply neutral is lost. Instantaneous response, no intentional time delay.
Ratings and real-world fit
The breaking capacity is 1500 A (Idm / Im), which handles most downstream fault levels in a final subcircuit; upstream coordination with an MCB or fuse is assumed for higher prospective fault currents. IP20 on the device body (finger-safe terminals), IP40 inside the modular enclosure — standard for a distribution board, not for wet washdown zones. The 8/20 µs impulse withstand of 3000 A per EN/IEC 61008-1 means it survives lightning-induced surges on the line side without damage.
Terminal and wiring notes
Neutral is on the left. Padlocking device provision for lockout/tagout. Toggle control with a contact position indicator — visible confirmation of contact state without removing the front cover.
Electrical durability is 15,000 cycles under AC-1 (resistive load); mechanical durability is 20,000 cycles. Complies with EN/IEC 61008-1.