DC-rated miniature circuit breaker, 1-pole B25
The Siemens 5SY5125-6CC12 is a 1-pole miniature circuit breaker from the 5SY5 series, rated 25 A with a B tripping curve. It is specifically rated for 220 V DC applications with a 10 kA breaking capacity — the DC rating is what distinguishes this unit from standard AC-only MCBs, making it suitable for DC distribution panels, UPS outputs, or photovoltaic combiner boxes where fault clearing under DC arc conditions requires a different contact geometry and arc chute design.
DC arc extinction and coordination
The 10 kA breaking capacity at 220 V DC is the headline figure — DC arcs do not self-extinguish at voltage zero crossings like AC, so the internal arc chute and contact material are engineered for sustained DC interruption. In a panel environment, this means the breaker can safely clear a bolted fault on a 220 V DC bus without welding contacts or cascading failure upstream. The B-curve (3-5× In magnetic trip) provides fast short-circuit response while tolerating moderate inrush from capacitive DC loads.
Panel integration
Snap-on mounting to standard 35 mm DIN rail per EN 60715. The 1-pole module occupies one 18 mm width unit. Wire terminals accept 0.75–25 mm² conductors (solid or stranded) with a box lug termination. Busbar comb slots are compatible with Siemens 5ST3 series pin busbars for grouped incoming supply.