The Siemens SIRIUS 3RV1031-4FB10 is a three-pole motor protection circuit breaker rated for 40 A continuous current with Trip Class 20, sized for a 3-phase motor load up to 18.5 kW at 400 V. It snaps onto a 35 mm DIN rail per DIN EN 50022 and terminates via screw-type box terminals on the main circuit, accepting solid conductors 2x (0.75... 16 mm²) or stranded 2x (0.75... 25 mm²).
Breaking capacity and coordination
Breaking capacity drops with system voltage: 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. At 400 V the 50 kA rating covers most industrial service-entrance fault levels; at 690 V the 4 kA figure still clears a low-impedance fault but demands upstream coordination — check selectivity with the feeding MCCB or fuse.
Trip class and protection features
Class 20 means the bimetal trip allows up to 20 seconds at 7.2× rated current — standard for general-purpose induction motors starting direct-on-line (pumps, fans, compressors). Phase failure detection is built in; ground fault detection is not, so a separate residual-current device is needed if the installation requires earth-leakage protection.
Power dissipation and thermal management
At full load in hot operating state the breaker dissipates 29 W total, 9.7 W per pole. In a crowded DIN-rail enclosure that heat adds up — allow natural convection or forced airflow if multiple units sit side by side with zero side clearance (the evidence lists 0 mm backwards and side clearance).
Sourcing and availability
This part is sourced and quoted to order through independent distribution. Submit an RFQ for current pricing and availability — the 40 A Class 20 rating and 18.5 kW at 400 V make it a direct fit for motor-protection BOM lines in that power band.