Motor Protection Breaker, 40 A, Class 10 — SIRIUS 3RV1031-4FA10
The Siemens 3RV1031-4FA10 is a SIRIUS motor protection circuit breaker rated for 40 A continuous current with a Class 10 trip curve, meaning it clears overloads fast enough to protect standard induction motors during start-up without nuisance tripping. It carries a 50 kA short-circuit breaking capacity at 400 V AC and is rated for 18.5 kW motor load at 400 V, so it can handle a direct-on-line motor start on a typical 400 V three-phase supply without needing an upstream fuse for fault levels up to 50 kA. Phase failure detection is built in — that's a real help on a line where a single-phase condition could cook a motor before the overload curve catches it.
Mounting and Integration
Snaps onto 35 mm DIN rail per DIN EN 50022 and can be mounted in any position, which gives the panel builder flexibility in tight cabinets. At 55 mm wide, 140 mm tall, and 149 mm deep, it takes up one standard modular slot — no surprises when laying out a row of motor starters. Screw-type box terminals on the main circuit accept 2x 0.75–16 mm² solid or 2x 0.75–25 mm² stranded, and the auxiliary circuit also uses screw terminals — standard stuff for a panel shop, no special tooling needed.
What the Ratings Mean for Your Panel
The 50 kA SCCR at 400 V means this breaker can safely interrupt a fault current up to that level without welding its contacts or rupturing — critical for a motor branch circuit where the available fault current might be high. Power dissipation runs 29 W total in hot operating state, or 9.7 W per pole — worth checking the thermal budget in a densely packed enclosure, especially if you're stacking several of these next to each other. The IP20 front protection is typical for a DIN-rail device inside a locked panel; it keeps fingers out but isn't rated for washdown environments. RoHS compliance date of 07/01/2006 means it meets the EU substance restrictions for lead, mercury, cadmium, and the usual six — no compliance surprise for a European-built machine.