The Siemens 3RV1031-4FA10-0BA0 is a SIRIUS motor protection circuit breaker rated for 40 A continuous current and 18.5 kW motor power at 400 V AC. It carries a CLASS 10 trip characteristic, meaning it will trip within 10 seconds under locked-rotor conditions — fast enough to protect standard induction motors from overheating during a stall. The 50 kA breaking capacity at 400 V AC means it can safely interrupt a fault current up to that level without upstream fuses needing to clear first, which simplifies panel coordination. Phase failure detection is built in, so the breaker will trip if one phase drops out — a common cause of single-phasing damage in delta-connected motors. Ground fault detection is not included, so if that is required, an external ground-fault module or relay must be added.
Mounting and integration
Mounts via screw or snap-on onto 35 mm DIN rail per DIN EN 50022. The 55 mm width and 140 mm height are standard for this SIRIUS frame size; depth of 149 mm leaves clearance for the screw-type box terminals on the main circuit and the auxiliary contact block on top. Zero clearance required at the back or sides, so adjacent devices can butt directly against it — no derating for side-by-side packing in a crowded panel. Screw terminals on the main circuit accept solid conductors up to 2x 16 mm² or stranded up to 2x 25 mm². The auxiliary and control circuit also uses screw terminals. Terminal capacity is generous for the 40 A rating — no need to pigtail down to a smaller wire.