Motor protection circuit breaker, 12.5 A, CLASS 10
The Siemens SIRIUS 3RV1021-1KA10-ZX95 is a motor protection circuit breaker designed for the thermal and magnetic protection of motors up to 5.5 kW at 400 V. Its 12.5 A continuous current rating and CLASS 10 trip characteristic mean it clears a stalled-rotor condition fast enough to protect standard IEC induction motors before winding temperature exceeds the insulation class — that is the core job this part is built for. Rated breaking capacity reaches 100 kA at 400 V AC, dropping to 42 kA at 500 V and 6 kA at 690 V. This tells you the available fault current the device can safely interrupt at the point of installation — at 400 V, it handles the full 100 kA without upstream fuses, which simplifies coordination in high-fault panels. Phase failure detection is built in. That means if one phase drops on a three-phase motor, the breaker trips before single-phasing cooks the winding — a standard requirement for motor protection under IEC 60947-4-1.
Mounting and panel integration
Mounts via screw or snap-on onto 35 mm DIN rail per EN 50022. The 45 mm width and 97 mm height fit a standard motor starter row; depth is 96 mm, so plan for at least 100 mm clearance behind the panel door. Any mounting position is allowed, which helps when the enclosure is tight on vertical space. Screw terminals on the main circuit accept solid or stranded conductors: 2x (1 … 2.5 mm²) and 2x (2.5 … 6 mm²), or AWG 14–10. The front face carries an IP20 rating — finger-safe but not washdown-rated; keep it inside a closed panel.