What this MCCB is and what it does
The Siemens 3RV1363-7EN10 is a SIRIUS molded-case circuit breaker (MCCB) designed specifically for starter combinations — meaning it's meant to sit upstream of a contactor and overload relay, handling motor branch-circuit protection as a single coordinated assembly. It's not a general-purpose distribution breaker; the electronic short-circuit trip is tuned for motor starting inrush, so you don't get nuisance trips on a 250 A AC-3 motor load at 400 V. Continuous current is 250 A, and the interrupting rating hits 120 kA at 400 V AC — that's a lot of fault current headroom for a motor branch. At 690 V it still holds 70 kA. The screw-type terminals on both main and auxiliary circuits mean you're wiring it with lugs, not bus bars; panel builders will appreciate the 105 mm width and 205 mm height, with screw fixing to the mounting plate.
Sizing and selectivity notes
The 250 A AC-3 rating at 400 V is the working number for motor duty — that's the current it'll carry continuously while switching a motor load. The 120 kA SCCR at 400 V means it can safely clear a fault up to that level without blowing apart or welding contacts, which is critical for coordination with downstream components. If you're feeding a panel with a transformer or generator that can deliver that kind of fault current, this breaker will hold the line.