Motor Protection Circuit Breaker, 40 A, Class 10 — SIRIUS 3RV1031-4FA10-ZW97
The Siemens 3RV1031-4FA10-ZW97 is a SIRIUS motor protection circuit breaker rated for 40 A continuous current with a Class 10 trip characteristic, meaning it protects standard induction motors during start-up by allowing up to 10 seconds of locked-rotor current before tripping — a common spec for pump, fan, and conveyor drives on 400 V lines. It breaks 50 kA at 400 V AC, which covers most industrial panel fault levels without requiring an upstream current-limiting fuse for SCCR compliance. Phase failure detection is built in, so a lost phase on the line side will trip the breaker and stop the motor before single-phasing damage occurs. Ground fault detection is not included — this is a straight thermal-magnetic overload and short-circuit protector, not a GFCI. Mounts via screw and snap-on onto 35 mm standard mounting rail per DIN EN 50022, and the IP20 front protection means it's safe for finger contact inside an enclosed panel.
Breaking Capacity and Coordination
Rated short-circuit 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 most common industrial distribution voltage — the 50 kA figure means this breaker can be applied on busways with up to 50 kA available fault current without needing a current-limiting backup fuse. The 690 V rating at 4 kA is marginal; if your panel feeds a 690 V motor and the SCCR at that bus exceeds 4 kA, you'll need a coordinated fuse ahead of it. The surge voltage resistance is rated at 6000 V, which aligns with IEC 60947-2 overvoltage category III for fixed-installation breakers.
Termination and Wiring
Main circuit terminals are screw-type box terminals accepting 2x solid conductors from 0.75 to 16 mm², or 2x stranded from 0.75 to 25 mm² plus a single 0.75 to 35 mm². For AWG, that's 2x 18 to 2 AWG solid or stranded, and a single up to 2 AWG. Fine-stranded wire with ferrule is accepted at 2x 0.75 to 16 mm² or a single 0.75 to 25 mm². The auxiliary and control circuit uses separate screw-type terminals. The product extension for an auxiliary switch is supported, so you can add a signal contact for PLC feedback or status indication without modifying the breaker body. Dimensions are 55 mm wide, 140 mm high, 149 mm deep — a standard three-pole SIRIUS frame that fits alongside contactors in a motor starter assembly.