The Siemens SENTRON 5SM9325-6KK01 is a 2-pole electronic residual current (RC) unit, type A, short-time delayed, rated 63 A at 400 V AC with a 30 mA tripping threshold. That 30 mA type A rating means it catches pulsating DC fault currents on top of sinusoidal AC — common downstream of single-phase rectifiers in VFDs, switched-mode supplies, or lighting ballasts. The short-time delay prevents nuisance tripping from transient surge currents that would otherwise take out a standard instantaneous RCD.
Full 63 A rating holds up to 45 °C ambient — at 40 °C and 45 °C it carries 58.59 A continuous. Above that it derates: 56.7 A at 50 °C, 54.81 A at 55 °C, 53.55 A at 60 °C, 52.29 A at 65 °C, and 50.4 A at 70 °C. The 2-pole form factor snaps onto standard DIN rail; no neutral switching on this variant since it's a 2-pole RC unit, not an RCBO.