The Siemens SIRIUS 3RV2031-4DA15 is a motor protection circuit breaker designed for screw and snap-on mounting onto 35 mm DIN rail per DIN EN 60715. It's rated CLASS 10 trip class, meaning it will trip within 10 seconds at 7.2× the thermal setting — fast enough to protect standard induction motors during a locked-rotor event without nuisance tripping on normal starts. Phase failure detection is built in, so a lost leg on the line side will drop the load before single-phasing cooks the winding.
Breaking capacity and voltage range
Rated operating voltage spans 20 to 690 V AC, covering low-voltage motor circuits from control transformers up to 690 V line supplies. The breaking capacity at 400 V is 30 kA — that's the fault current it can safely interrupt without welding contacts or venting plasma. At 690 V it still holds 3 kA, which is enough for most industrial distribution downstream of a transformer. The 55 mm width and 149 mm depth fit standard motor starter cubbies; the M6 main contact screws accept 2x (0.5 to 2.5 mm²) conductors.