The Siemens SENTRON 5SY5104-7CC11 is a 1-pole miniature circuit breaker rated for 4 A with a C tripping characteristic, designed for DC operation up to 250 V and a breaking capacity of 10 kA at 220 V DC per IEC 60947-2. The C-curve means it trips at 5 to 10 times rated current — standard for moderate inrush loads like control transformers or small DC motor drives — so a 4 A unit clears a sustained 20–40 A fault quickly while ignoring brief startup spikes. This is a dedicated DC-rated breaker, not an AC-rated unit used on DC. The 10 kA interrupting rating at 220 V DC is the figure that governs fit for a DC bus or battery-backed circuit; an AC-only breaker would lack the arc-quenching capability for DC faults. The part also carries a 230/400 V AC rating at 10 kA, but the DC spec is the headline here.
The 5SY5104-7CC11 is explicitly designed for railway applications — the product designation and suitability field both flag this. That means it meets the vibration and shock profile of rail environments: ±1 mm at 5 to 25 Hz and 50 m/s² at 25 to 150 Hz per IEC 60068-2-6. If you're sourcing for a locomotive auxiliary panel, signaling cabinet, or wayside power supply, this is the variant that carries the rail-specific qualification. Mounting is the standard 18 mm modular width (1 MWU) on DIN rail, with a quick-assembly fastening system and any mounting position allowed. Polarity must be observed on the DC supply connection.