What this SIRIUS breaker does on the line
The Siemens 3RV1021-0CA10-0FJ0-ZX95 is a SIRIUS motor protection circuit breaker built for small-horsepower three-phase motors — at 400 V AC it's rated for 0.06 kW motor output, so think fractional-horsepower pumps, small fans, or conveyor drives that draw 0.25 A continuous. Trip class CLASS 10 means it clears an overload in under 10 seconds at 7.2× the set current — that's the standard for standard-duty induction motor starts, not for high-inertia loads that need a slower CLASS 20 or 30 curve. The interrupting rating is a flat 100 kA across 240 V, 400 V, 500 V, and 690 V AC — that's a lot of fault-current headroom for a 0.25 A breaker, meaning it handles high available short-circuit current on a panel fed by a large transformer without needing an upstream current-limiting fuse.
Screw-type terminals on the main circuit accept 1…2.5 mm² solid or stranded (two wires per clamp) or AWG 14…10 — fine for the control wiring you'd run to a 0.25 A motor. Depth is 96 mm, height 97 mm — it sits flush with other SIRIUS 3RV1 breakers on the rail, so no staggered mounting for mixed sizes.
It includes an auxiliary switch (the -0FJ0 suffix), so you get a status contact for the PLC or annunciator without adding a separate block — saves a DIN slot and wiring time. Rated for 690 V AC-3 and surge voltage resistance is 6 kV.