What it is and where it lands
The Siemens 3RV2031-4XB10 is a SIRIUS motor protection circuit breaker designed to protect motor branch circuits against overloads and short circuits. It mounts on a 35 mm DIN rail per DIN EN 60715 via screw or snap-on fastening, so it fits standard industrial control panels without extra bracketry. The 55 mm width and 149 mm depth keep the footprint manageable for dense panel layouts. Rated for motor protection duty, it includes phase failure detection — if one phase drops out, the breaker trips before the motor single-phases and burns up. No ground fault detection here, so this is a straightforward motor branch protector, not a combined GFCI. The Trip Class 20 means it allows a 20-second overload before tripping at 7.2× rated current. That's standard for general-purpose induction motors starting conveyors, pumps, and fans — enough inrush time without nuisance trips on normal starts.
Breaking capacity — what the numbers mean in the panel
At 400 V the 3RV2031-4XB10 interrupts 30 kA symmetrical. That is the SCCR the breaker can clear without welding contacts or venting plasma into the enclosure. On a 480 V system it still carries 59 A continuous and holds a 30 kA interrupt rating at 400 V — check your available fault current against the 30 kA ceiling. At 240 V the interrupting rating jumps to 100 kA; at 690 V it drops to 2 kA. The 100 kA at 240 V covers high-fault installations near large transformers. The 2 kA at 690 V is adequate for most 690 V industrial networks where available fault current is lower. The motor switching frequency is limited to 15 operations per hour at AC-3 duty. That is fine for a pump or fan that starts a few times an hour, but not for a jogging application or a reversing drive that cycles every minute.
Mounting and wiring in the field
Screw and snap-on mounting onto 35 mm DIN rail per DIN EN 60715. The snap-on feature means you can clip it onto the rail without tools — useful when retrofitting in a live panel where you want to minimise time with the screwdriver. Screw terminals on the main circuit accept 2× 1–35 mm² or 1× 1–50 mm² solid or stranded wire. M6 terminal screws on the main contacts handle the torque for higher-current connections. Clearance requirements: 50 mm above and below the breaker, 10 mm at the sides. That is tight enough for most enclosures — the side gap is the limiting factor if you are packing multiple breakers side by side. Mounting position is any orientation, which simplifies panel layout when space is awkward. Operating temperature range is -20 to +60 °C; storage and transport range is -50 to +80 °C, so it survives cold warehouses and hot shipping containers.