The Siemens 5SY7125-8CC is a 1-pole SENTRON miniature circuit breaker with a D tripping characteristic, rated 25 A at 400 V AC. The D-curve means it tolerates brief inrush currents up to 10–20× rated — designed for motor and transformer branch circuits where the start-up surge would nuisance-trip a B or C curve. The 25 kA breaking capacity per IEC 60947-2 tells you it can safely interrupt a fault current up to that level without welding contacts or cascading damage upstream.
Snaps onto DIN rail via the quick-assembly system, occupying a single 18 mm width unit. Depth is 76 mm, installation depth 70 mm — fits standard distribution boards without crowding the gland plate. Terminals accept solid or stranded conductors from 0.75 to 35 mm²; tightening torque is 2.5–3.5 N·m, typical for screw terminals on this class of MCB. IP20 with connected conductors, so it belongs inside a closed panel, not exposed to washdown.
Rated for 50/60 Hz, overvoltage category III, and suitable for mechanical engineering and industrial environments. Ambient temperature range –25 to +55 °C; storage from –40 to +75 °C. Halogen-free and silicon-free construction — relevant for clean-room or sensitive electronic co-location. Sealable terminals allow tamper-proofing after commissioning.