Rated current and thermal derating
The Siemens 5SM9445-0KK is a SENTRON residual current unit (RC unit electronic) in the 5SM9 design, rated for 63 A at 230/400 V AC, 50 Hz, with a 100 mA tripping residual current for type AC fault currents. The rated current holds at 58.59 A up to 45 °C ambient, then derates through 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 — a thermal curve that governs panel fill and adjacent-device spacing when the enclosure ambient climbs above 40 °C.
Compliance and documentation
As a SENTRON-branded Siemens component, the 5SM9445-0KK is supplied with a declaration of conformity covering the applicable IEC/EN standards for residual current devices. The type AC designation means it detects sinusoidal AC fault currents only — not pulsed DC or smooth DC — so the application must be limited to AC circuits without rectified loads downstream. The 4-pole design switches all four poles (L1, L2, L3, N) and is intended for three-phase systems up to 400 V line-to-line.