What this SIRIUS motor protection circuit breaker does
The Siemens 3RV1021-0FA10-0FJ0 is a SIRIUS motor protection circuit breaker rated for 0.5 A continuous current, designed to protect three-phase motors against overload, short-circuit, and phase failure. Its Class 10 trip curve means it disconnects within 10 seconds at 7.2× the set current — fast enough to protect standard induction motors during a locked-rotor event without nuisance tripping on normal starting inrush. The 100 kA breaking capacity at 400 V AC lets it safely interrupt high-fault-current bolted shorts upstream of the motor starter, so the panel's upstream feeder breaker doesn't need to be coordinated for the full fault level. Phase failure detection is built in, so a single blown fuse or dropped phase on the line side will trip the breaker rather than letting the motor single-phase and overheat.
Mounting and panel fit
Mounts via screw or snap-on onto 35 mm standard mounting rail per DIN EN 50022. The 45 mm width and 96 mm depth mean it occupies one standard 45 mm module slot on the rail — no extra side clearance needed (0 mm at the side; 0 mm backwards,). Any mounting position is permitted, which helps when laying out a dense panel where vertical or horizontal orientation matters for wire routing. Screw-type terminals on the main current circuit accept solid or stranded conductors: 2× (1…2.5 mm²) and 2× (2.5…6 mm²). The IP20 front is standard for enclosed panels; no additional finger-safe shrouding required behind the gland plate.
Environmental and mechanical limits
Operating temperature range is -20 to +60 °C; storage and transport tolerate -50 to +80 °C. Shock resistance is 25 g / 11 ms, adequate for machine-mounted panels on presses or conveyors. Maximum operating altitude is 2 000 m without derating. The mechanical endurance of the main contacts is typically 100 000 operations, and the maximum switching frequency at AC-3 duty is 15 operations per hour. Power dissipation at rated current in hot operating state is 5.5 W total, 1.8 W per pole.