What it is and what it does
The Siemens 3RV1031-4HB15 is a SIRIUS motor protection circuit breaker, designed for motor protection in main current circuits. It switches and protects motors up to 22 kW at 400 V AC-3 duty, with a continuous current rating of 50 A. Trip Class 20 means it allows a motor starting current of up to 7.2x the thermal setting for 20 seconds before tripping — a good match for standard induction motors driving pumps, fans, or conveyors that don't have extended start times. It includes phase failure detection but no ground fault detection, so it handles the most common motor fault — a lost phase — without nuisance tripping on leakage.
Breaking capacity — what it means for your panel
The 3RV1031-4HB15 delivers 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 supply in Europe and Asia — 50 kA SCCR gives you headroom for high-fault panels without needing a current-limiting upstream breaker. Compared to the 3RV2021-4NA25, which is a newer SIRIUS 3RV2 frame with a different trip curve and higher breaking capacity at 690 V, this 3RV1 series part is the established choice for 400 V distribution where the 50 kA rating is sufficient. The 3RV2 has a slightly different footprint — verify DIN rail spacing if swapping.
Mounting and wiring
Fastens via screw and snap-on onto 35 mm standard mounting rail per DIN EN 50022. Mounting position is any, so it fits tight enclosures. Width is 55 mm, height 140 mm, depth 149 mm — plan your gland plate and wireway clearance accordingly. Main circuit terminals accept solid 2x (0.5...1.5 mm²) and 2x (0.75...2.5 mm²), or stranded 2x (0.75...25 mm²) and 1x (0.75...35 mm²). Auxiliary and control circuit terminals are screw-type. AWG equivalents for main contacts: 2x (18...2), 1x (18...2). IP20 on the front — fine for enclosed panels; not rated for washdown or outdoor exposure without an additional enclosure.
Environmental and compliance
Substance prohibitance date of 07/01/2006 aligns with RoHS compliance. Storage temperature range -50 to +80 °C, operation -20 to +60 °C, transport -50 to +80 °C. Shock resistance rated at 25g / 11 ms.