The Siemens 5SM3324-4BG is a 2-pole residual current operated circuit breaker (RCCB) with Type B sensitivity, rated at 40 A and 30 mA residual current for 400 V AC systems. The short-time delayed characteristic means it's built for circuits where brief inrush or leakage pulses are normal — think motor drives, UPS systems, or industrial gear with switching power supplies — so it won't nuisance-trip on transient earth faults that a standard instantaneous RCCB would catch.
What the ratings mean for fit
Type B detection covers AC, pulsating DC, and smooth DC residual currents up to the rated 30 mA threshold. That's the key spec for variable-frequency drives, inverters, or any load where a rectifier stage can generate DC fault current back to ground — a Type A or AC device would miss that entirely. The 40 A line rating matches the main feed for a small distribution board or a heavy sub-panel; the 30 mA trip level is the standard for personnel protection (30 mA is the IEC threshold for fibrillation risk). On a 400 V three-phase system the 2-pole construction breaks both phase conductors, leaving the neutral through.
Mounts on standard DIN rail in a distribution board or sub-panel. The 2-pole width (2 module spaces) fits alongside MCBs and other modular devices. Terminal capacity and torque specs follow the standard Siemens 5SM family footprint — no special busbar or adapter required for a typical residential or light-industrial enclosure.