The Schneider Electric A9R31440 is a 4-pole Acti9 iID residual current circuit breaker (RCCB) rated for 40 A continuous current with a 30 mA earth-leakage trip threshold. The Type A-SI (Super Immunised) classification means it handles pulsed DC fault currents from electronics (VFDs, switched-mode supplies) without nuisance tripping — a common pain point in modern industrial panels.
The 30 mA sensitivity is the standard for personnel protection (direct-contact shock prevention) per IEC 60364. The 40 A rated current matches a 3-phase outgoing feeder for a sub-distribution board or a large machine supply. Breaking capacity is rated at Idm 1500 A and Im 1500 A — adequate for most final circuits where the upstream MCB or fuse already limits fault current below that level. Type A-SI (Super Immunised) adds immunity to high-frequency leakage currents and transient surges that would trip a standard Type A RCCB. The voltage-independent tripping mechanism means the device detects leakage even if the phase voltage collapses — it does not rely on an electronic circuit for the trip decision. This is a key reliability feature for safety-critical circuits. The 8/20 µs impulse withstand of 3000 A confirms it survives lightning-induced or switching surges on the line side without internal damage.
Clip-on DIN rail mounting, neutral on the left side. Terminals accept up to 35 mm² rigid or 25 mm² flexible wire; strip length 14 mm, tighten to 3.5 N·m. The 72 mm width (8 x 9 mm pitches) fits standard modular enclosure spacing.