What it is and what it does
The Siemens 3RV2031-4VB15 is a SIRIUS motor protection circuit breaker designed to protect three-phase induction motors against overload and short-circuit. It combines a thermal-magnetic overload relay and a high-breaking-capacity circuit breaker in one device, eliminating the need for separate components in the motor branch circuit. The breaker is rated for a supply voltage range of 20 to 690 V and offers a breaking capacity of 30 kA at 400 V — enough to handle most industrial fault levels without cascading upstream. Trip Class 20 means it allows a longer starting time for high-inertia loads (pumps, fans, conveyors) before tripping on overload.
Key ratings and what they mean for fit
The 30 kA breaking capacity at 400 V is the headline number: it tells you this breaker can safely interrupt a short-circuit fault up to that current level without welding contacts or rupturing the enclosure. At 690 V the capacity drops to 2 kA, so if your panel feeds a 690 V motor, verify the available fault current stays under that limit. The auxiliary contact ratings cover 24 V at 1 A, 60 V at 0.15 A, and 230 V at 0.5 A — enough to signal a trip to a PLC or annunciator. Phase failure detection is built in, so the breaker will trip if one phase drops out, preventing single-phasing damage. No ground-fault detection; if that's required, add an external ground-fault module.
Mounting and integration
Mounts via screw and snap-on onto a 35 mm DIN rail per DIN EN 60715. The 55 mm width occupies three standard 18 mm module spaces, so plan your DIN-rail layout accordingly. Clearance requirements: 50 mm above and below, 10 mm at the sides. Any mounting position is allowed. Main circuit terminals accept 2x (0.5 to 1.5 mm²) or 2x (0.75 to 2.5 mm²) solid or stranded wire. The main contact terminal size is M6. Operating temperature range is -20 to +60 °C; storage and transport range is -50 to +80 °C.