What it is and what it does
The Siemens 3RV1031-4FA15 is a SIRIUS motor-protection circuit breaker rated for 40 A continuous current and 18.5 kW at 400 V AC, with a Class 10 trip characteristic. Class 10 means it will trip within 10 seconds at 7.2× rated current, which protects standard induction motor windings during a stall or locked-rotor condition without nuisance tripping on normal starting inrush. The 50 kA breaking capacity at 400 V AC means it can safely interrupt a bolted fault up to that level without the upstream fuse or breaker needing to clear it first — useful for high-fault panels near a transformer. Phase failure detection is built in, so if one phase drops on a three-phase motor, the breaker opens before single-phasing cooks the winding. Ground fault detection is not included — that would need a separate module or a different breaker variant.
Mounting and panel fit
Mounts via screw and snap-on onto 35 mm DIN rail per EN 50022. Zero clearance on the sides and rear. Width is 55 mm, height 140 mm, depth 149 mm. IP20 on the front means finger-safe from the panel face, but the terminals are live when the breaker is on — standard for a motor-protection device inside a locked enclosure. Operating temperature range is -20 to +60 °C; storage and transport from -50 to +80 °C. Shock rated at 25 g for 11 ms. Mounting position is any.
Terminal wiring
Main circuit terminals are screw-type with box terminals, accepting stranded wire from 2x (0.75... 25 mm²) up to 1x (0.75 … 35 mm²), or AWG 2x (18... 2) to 1x (18... 2). Auxiliary and control circuit terminals are also screw-type, accepting solid wire 2x (0.5... 1.5 mm²) and 2x (0.75... 2.5 mm²). The auxiliary switch is transverse design and the product extension for an auxiliary switch is available. Auxiliary contact ratings: 1 A at 24 V, 0.5 A at 230 V, 0.15 A at 60 V. These are the switching capacities for the built-in or add-on auxiliary contacts — useful for feeding a PLC input or a contactor coil.