DC-rated miniature circuit breaker for control-circuit protection
The Siemens 5SY5104-6CC12 is a 1-pole miniature circuit breaker from the 5SY5 series, carrying a B4 tripping curve and a 220V DC rating with 10kA breaking capacity. The 220V DC rating is the key selection parameter here: standard AC-rated MCBs may not extinguish a DC arc reliably at this voltage, so this unit's DC-optimised arc chamber and contact gap are what make it fit for railway, UPS, or process-control DC auxiliaries.
The 1-pole width (roughly 18 mm per pole) keeps panel fill factor tight — a single unit occupies one module space.