The Siemens 5SJ4118-7HG42 is a SENTRON miniature circuit breaker (MCB) from the 5SJ4 family, designed for 1-pole protection with a C tripping characteristic. It breaks fault currents up to 10 kA per EN 60898 and 15 kA per IEC 60947-2 at 400 V AC, making it a standard choice for branch-circuit protection in industrial control panels and distribution boards.
At 18 mm wide (1 modular unit), this MCB snaps onto a standard DIN rail and fits any 1-pole slot in a SENTRON or equivalent distribution board. The C-curve (per EN 60898) is the go-to for general-purpose industrial loads — it allows 5–10x rated current for a brief magnetic trip delay, so it won't drop out on a motor start or capacitor bank inrush. The 10 kA breaking capacity under EN 60898 covers most commercial and light industrial installations; the 15 kA rating per IEC 60947-2 gives headroom for higher-fault panels (e.g., near a large transformer).