The Siemens 5SU1674-7DK82 is a SENTRON RCBO — a combined residual-current circuit breaker with overcurrent protection — in the Super Resistant K design, rated 125 A at 30 °C on a 4-pole (4P) frame. It trips on residual fault currents at 300 mA, Type B+, which means it catches smooth DC fault currents plus higher-frequency AC components, not just the 50/60 Hz sine wave a standard AC type would miss. That matters on drives, UPS feeds, or PV inverters where DC fault current can blind a basic RCD.
At 40 °C ambient the continuous rating drops to 115.62 A; at 50 °C it's 106.25 A; at 60 °C it's 96.25 A.