RCD for 400 VAC panels — 40 A, 30 mA, type AC
The Siemens SENTRON 5SM9322-0KK is a 2-pole residual current unit (RC unit electronic) rated 40 A with 30 mA sensitivity, type AC, designed for instantaneous tripping on 400 VAC 50 Hz supplies. The 30 mA threshold covers personnel protection in standard industrial and commercial circuits where sinusoidal AC fault currents are expected — the most common RCD class for general socket-outlet and lighting circuits. Power dissipation runs 0.8 W per pole in the hot operating state, which matters for thermal coordination inside a crowded DIN-rail enclosure.
Two-pole form factor snaps onto standard DIN rail. The 400 VAC 50 Hz supply is fixed — not a wide-range input — so verify the line frequency matches before committing the BOM line.