The Siemens SENTRON 5SY5125-7KK11 is a 1-pole miniature circuit breaker with a 25 A rated current and C-curve tripping characteristic, giving it a magnetic trip threshold of 5–10× In — suited for moderate inrush loads like small motors, lighting banks, and transformer primaries where the start-up surge exceeds a B-curve's range but doesn't need the D-curve's 10–20× headroom. Breaking capacity is 10 kA per EN 60898 (AC) and 10 kA per EN 60898-2 (DC), which means it safely interrupts fault currents up to that level without welding contacts or cascading upstream — a standard fit for most residential, commercial, and light industrial distribution boards where the prospective short-circuit current stays under 10 kA. The part carries a universal-current rating (AC and DC), so it handles DC circuits up to 220 V with the same 10 kA interrupting capacity, but note the supply polarity: AC can be fed from either side, while DC requires correct polarity per the marking on the device. Temperature derating is published from 35 °C upward: full 25 A at 35 °C, then 23.8 A at 40 °C, dropping to 21.2 A at 60 °C.
Functional marking per EN 61346-2 and IEC 81346-2: letter F (protective device). The part carries the SENTRON brand and is listed as a miniature circuit breaker in the Siemens catalog.