Motor protection circuit breaker, 40 A — CLASS 20 trip, 50 kA at 400 V
The Siemens SIRIUS 3RV1031-4FB15-ZX95 is a motor protection circuit breaker rated for 40 A continuous current, designed to protect three-phase induction motors up to 18.5 kW at 400 V. Its CLASS 20 trip curve allows for longer starting times — typical for high-inertia loads like conveyors, fans, or compressors that draw sustained inrush without nuisance tripping. Short-circuit breaking capacity is 100 kA at 240 V AC, 50 kA at 400 V AC, 10 kA at 500 V AC, and 4 kA at 690 V AC — meaning it can safely interrupt faults up to those levels without cascading upstream, which simplifies panel coordination in high-fault installations. Phase failure detection is built in, and the unit includes a transverse auxiliary switch design with product extension capability, so you can add auxiliary contacts or shunt trips without replacing the base breaker.
Mounting and wiring — DIN rail snap-on, screw terminals up to 35 mm²
Mounts via screw and snap-on onto 35 mm standard mounting rail per DIN EN 50022. The 55 mm width and 140 mm height fit a standard 3-module footprint; depth is 149 mm. Mounting position is any, and backwards / side clearances are zero — so it can be packed tight in a panel without derating for airflow. Main circuit terminals are screw-type with box terminals, accepting stranded wire from 2x (0.75... 25 mm²) or 1x (0.75 … 35 mm²). Solid wire is 2x (0.5... 1.5 mm²) or 2x (0.75... 2.5 mm²). AWG equivalents for main contacts are 2x (18... 2) or 1x (18... 2). Auxiliary and control circuits use separate screw-type terminals. Power dissipation in hot operating state is 29 W — plan for that heat load in the enclosure, especially when multiple breakers are ganged.
Environmental and compliance
Operating temperature range is -20 to +60 °C; storage and transport range is -50 to +80 °C. Shock resistance is 25 g / 11 ms. Protection class on the front is IP20 — suitable for enclosed panel use, not for washdown environments. RoHS compliance is indicated by substance prohibitance date of 07/01/2006. Ground fault detection is not included — this is a motor-protection-only device, not a ground-fault circuit interrupter.