What this SIRIUS 3RV1021-1JA10-0FJ0-ZX95 is and what it does
This is a Siemens SIRIUS motor protection circuit breaker — order code 3RV1021-1JA10-0FJ0-ZX95 — rated for 10 A continuous current with a CLASS 10 trip characteristic, meaning it clears overloads fast enough to protect standard induction motors during start-up without nuisance tripping on the inrush. It switches a 4 kW motor at 400 V AC (AC-3 duty) and carries a 100 kA short-circuit breaking capacity at 400 V, so it can interrupt a fault up to that level without upstream devices needing to clear it — that's the SCCR the panel label needs. Phase failure detection is built in, which means if one phase drops on a three-phase motor, the breaker trips before single-phasing cooks the winding. That's a standard feature on SIRIUS 3RV1 breakers, not an add-on accessory.
Mounting and panel fit
Snaps onto 35 mm DIN rail per DIN EN 50022 — screw and snap-on mounting, no tools needed for the rail. The 45 mm width and 97 x 96 mm height/depth mean it takes one standard 45 mm module slot in a panel; plan the gland plate and fill factor accordingly. Mounting position is any, so it can go sideways or upside-down in a tight enclosure. IP20 on the front — finger-safe for the panel face, but not washdown-rated; keep it inside a cabinet. Terminals accept solid and stranded copper: 2x (1 … 2.5 mm²) and 2x (2.5 … 6 mm²) per clamp, with AWG equivalents 2x (14 … 10) for the main contacts. Finely stranded with ferrule is also supported. That covers most motor feeder cables up to 6 mm².
Environmental and mechanical limits
Operating temperature range is -20 to +60 °C; storage and transport handle -50 to +80 °C. Shock-rated at 25g / 11 ms — tough enough for machine-mounted panels on presses or conveyors. Maximum operating altitude is 2 000 m without derating. Above that, you'd need to account for reduced air density on the arc extinction and thermal dissipation. Power dissipation at rated current in hot state is 9.25 W total, or 3.1 W per pole. That's warm but manageable in a ventilated enclosure; factor it into the panel thermal budget if you're packing several in a row.