What it is and what it does
The Siemens 3RV2031-4XB15 is a SIRIUS motor protection circuit breaker designed for motor protection, with phase failure detection built in and no ground fault detection. Rated operating voltage spans 20 to 690 V, and the breaker carries a CLASS 20 trip characteristic — meaning it allows a 20-second overload before tripping, which matches standard NEMA and IEC motor starting profiles for medium-inertia loads like pumps and compressors. Breaking capacity at 400 V is 30 kA, sufficient for most industrial distribution panels with typical transformer sizes up to 1.6 MVA; at 690 V it still interrupts 2 kA, covering high-voltage motor circuits in European 690 V networks.
Mounting and panel fit
Fastens via screw and snap-on mounting onto 35 mm DIN rail per DIN EN 60715, with any mounting position allowed — no derating needed for horizontal or inverted orientation. Width is 55 mm, depth 149 mm, height 140 mm. The 55 mm width occupies three standard 18 mm DIN-rail module spaces, so plan for three slots in your enclosure layout. Clearance requirements: 50 mm above and below for arc venting and cable entry, 10 mm at the sides.