The Siemens 5SP4391-7 is a SENTRON 5SP miniature circuit breaker — 3-pole, C-curve, rated 100 A with a 10 kA breaking capacity per EN 60898 at 400 VAC. The C characteristic (5–10× In magnetic trip) suits it for mixed loads where motor inrush and lighting ballasts share the circuit — common in distribution sub-panels feeding contactor panels or small VFD banks.
The 4.5 modular-width footprint (81 mm wide) is wider than a typical 3-pole MCB — check your rail space if you're retrofitting into a crowded enclosure.
The C-curve trips between 5 and 10 times rated current, so a 100 A C-curve breaker holds through a 500–1000 A inrush — fine for groups of contactors or small transformers, but verify against your specific load's starting current.