What it is — and what the ratings mean for fit
The Siemens SENTRON 5SY5140-7KK11 is a 1-pole miniature circuit breaker with a C tripping characteristic, designed for universal-current operation (AC/DC) and built to railway application standards. The C-curve means it trips at 5–10 times rated current — the standard choice for moderate inrush loads like small motors, transformers, and lighting banks. Breaking capacity sits at 10 kA per EN 60898 and 15 kA per IEC 60947-2 at DC, so it handles fault currents up to that level without welding contacts or cascading upstream. That 15 kA DC rating is the one to watch if you're protecting a DC bus or battery-backed circuit — the EN number alone undersells it.
Panel fit and mounting
Snaps onto DIN rail via the quick-assembly system — no tools needed for the rail, just a screwdriver for the terminals. At 18 mm wide (1 modular width) and 70 mm installation depth, it leaves room for adjacent breakers and wiring ducts in a crowded enclosure. The combined terminal top and bottom accept conductors from either side, which saves a bend when you're landing the feed. Mounting position is any, so you can run it sideways in a shallow gland-plate layout without derating the thermal trip.