The Siemens 5SM9332-6KK is a SENTRON RC unit electronic — a 3-pole residual current device (RCD) with a 40 A rated current and 30 mA trip threshold, designed for 400 V AC systems. The 30 mA sensitivity is the standard for personnel protection (indirect contact) per IEC 60364.
Thermal derating and continuous current
The 5SM9332-6KK carries a nominal 40 A rating, but the continuous current it can pass without nuisance tripping depends on the ambient temperature inside the enclosure. At 40 °C it's rated for 37.2 A; at 45 °C it holds at 37.2 A; at 50 °C it drops to 36 A; at 55 °C it's 34.8 A; at 60 °C it's 34 A; at 65 °C it's 33.2 A; and at 70 °C it's 32 A. If this unit is going into a crowded DIN-rail panel with other heat sources, use the 50 °C or 55 °C column for your load calculation — the nominal 40 A only applies at the reference ambient (typically 30 °C or 35 °C, per the standard).
This is a 3-pole unit in the 5SM9 design family, intended for DIN-rail mounting in a distribution board or sub-distribution panel. The 30 mA trip and type A characteristic make it suitable for circuits feeding single-phase electronics where standard AC-only RCDs (type AC) would be blind to pulsating DC fault currents. No neutral conductor switching — it's a 3-pole device for 3-phase 400 V systems without switched neutral.