What this SIRIUS breaker does
The Siemens SIRIUS 3RV2031-4VA10-ZX95 is a motor protection circuit breaker designed to protect three-phase induction motors against overload, short circuit, and phase failure. Its Trip Class 10 characteristic means it will trip within 10 seconds at 7.2× the thermal setting — fast enough to protect a motor winding during a locked-rotor event without nuisance tripping on normal start-up. The interrupting capacity of 30 kA at 400 V and 100 kA at 240 V gives it enough fault-clearing muscle for most industrial distribution panels, so you don't need an upstream fuse for SCCR compliance up to those levels.
Mounting and panel fit
This breaker snaps onto a 35 mm DIN rail per DIN EN 60715 and can also be screw-mounted. The 55 mm width and 149 mm depth mean it occupies one standard 55 mm module slot on the rail — plan your gland-plate clearance accordingly, especially if the panel door has a deep interlock handle. Mounting position is any, so vertical or horizontal rail orientation is fine. Clearance requirements: 50 mm upwards, 50 mm downwards, 10 mm at the side, and zero forwards or backwards — that side gap is tight, so keep adjacent devices from crowding the arc-chamber vent.
Key ratings and what they mean for your motor
The Class 10 trip is the one that decides motor protection fit. A Class 10 breaker is designed for motors with short acceleration times — typically pumps, fans, and compressors that reach full speed in under 10 seconds. If your motor has a high-inertia load (flywheel, centrifuge) that takes longer to start, you'd need a Class 20 or 30 breaker to avoid nuisance tripping. Phase failure detection is built in, so the breaker will trip if one phase drops out — that's standard on SIRIUS motor-protection breakers, but not all brands include it at this level. The maximum switching frequency at AC-3 duty is 15 operations per hour, which is fine for manual start/stop or contactor-backed control; don't use this breaker as a cycled starter for a rapid-reversing application.