The Siemens SENTRON 5SM9332-0KK is a 3-pole residual current unit (RC unit electronic) rated 40 A with a 30 mA trip threshold, type AC, for 400 V AC / 50 Hz supply. This is the component that sits downstream of the main breaker or upstream of a sub-distribution board where you need earth-fault protection on a three-phase line.
The 40 A continuous rating (In) sets the maximum load current the RC unit can carry without overheating — sized for a 40 A feeder, not a 63 A one. The 30 mA residual operating current (IΔn) is the standard sensitivity for personnel protection (30 mA threshold per IEC 60364 against fatal shock). The 400 V AC / 50 Hz supply voltage matches standard European three-phase distribution panels (230/400 V networks). Power dissipation is 0.8 W per pole in hot operating state — negligible for thermal budgeting inside a crowded enclosure, but worth summing across all poles (2.4 W total) if you're calculating cabinet internal temperature rise.
Panel integration
Its 3-pole form factor occupies three modular-width units (each 18 mm, so 54 mm total). The instantaneous design means it coordinates with upstream overcurrent devices on the time-current curve — no intentional delay to stack against a selective main RCD. Wire it as a stand-alone residual current device or combine it with a matching SENTRON MCB (e.g., a 5SL or 5SY series) to form an RCBO assembly.