The Siemens SENTRON 5SM9635-6KK is a 3-pole residual current unit (RC unit electronic) rated at 63 A with a 300 mA tripping threshold, designed for 230/400 V AC supply. It's a type A device, meaning it detects sinusoidal AC residual currents plus pulsating DC residual currents — the standard choice for single-phase rectifier loads like switching power supplies, VFDs, and UPS-fed equipment where type AC alone isn't sufficient. The instantaneous design means it trips without a time delay, so it's suited for direct protection of circuits where selectivity against transient earth faults isn't required. It's part of the SENTRON 5SM9 family, which is the current-production RC unit platform from Siemens.
Temperature derating
The 63 A rating holds at 40 °C and 45 °C (58.59 A per the spec table), then begins to step down: 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. If this unit lives in a non-air-conditioned panel near ovens, drives, or a sunny roof, the 50 °C or 55 °C row is the one that governs the real load — not the 63 A nameplate. A 48 A continuous load is fine; a 60 A heater bank needs a bigger unit or forced ventilation to keep the internal temperature below 40 °C.
Panel integration
The 5SM9 RC units snap onto DIN rail and occupy three modular width units. They pair mechanically with SENTRON 5SY MCBs to form a combined RCBO assembly.