What it is and what it does
The Siemens SIRIUS 3RV2031-4JA10-ZW97 is a motor protection circuit breaker — the device that sits between the contactor and the motor in a standard IEC starter assembly, providing both short-circuit and overload protection in one package. It is designed for motor protection, not general distribution, which means its trip curve is shaped to match induction motor inrush and thermal characteristics. The CLASS 10 trip class means it will trip within 10 seconds at 7.2× the thermal setting — fast enough to protect a standard squirrel-cage motor during a locked-rotor event, but slow enough to ride through normal starting current without nuisance tripping. This is the standard choice for most conveyor, pump, and fan applications. Phase failure detection is built in, so a single-phased motor will be taken offline before winding damage sets in. Ground fault detection is not included — that would require an external core-balance relay or a separate ground-fault module.
Breaking capacity and selectivity
The interrupting ratings are given at multiple voltages, which matters for panel coordination. At 240 V it can clear 100 kA; at 400 V it handles 30 kA; at 500 V it drops to 4 kA; at 690 V it manages 2 kA. The 30 kA at 400 V is the figure most European panel builders will check first — it determines whether this breaker can be used without a current-limiting upstream fuse in a typical 400 V industrial supply with a 25 kA prospective fault level. Motor power ratings: 18.5 kW at 230 V, 25 hp at 220/230 V, 50 hp at 460/480 V. These are the AC-3 (squirrel-cage motor starting) ratings that govern the motor FLA it can protect.
Mounting and panel integration
Mounts via screw and snap-on onto 35 mm DIN rail per DIN EN 60715. The 55 mm width and 149 mm depth are the dimensions that matter for panel layout — it occupies a single 55 mm module on the rail. 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, 0 mm forwards and backwards. The side clearance of 10 mm is tight — adjacent devices can be butted close, but the 50 mm vertical clearance above and below is needed for arc-quenching and heat dissipation. Main circuit terminals accept 2× (1–35 mm²) or 1× (1–50 mm²) solid or stranded copper. Screw-type terminals with M6 thread.