What the part is on the BOM
The Siemens SIRIUS 3RV1021-0BA10-0FJ0 is a 3-pole motor protection circuit breaker in the 3RV1 frame, designed for motor protection with a CLASS 10 thermal trip response, so it sits on the feeder side of small fractional-horsepower motor starters where overload and short-circuit protection live in a single device.
Protection behaviour and operating envelope
Phase failure detection is present and ground fault detection is not, which means the breaker will trip on a lost phase but will not signal an earth-leakage event; if the application needs residual-current coverage, that has to be staged upstream or downstream with a separate device. An auxiliary switch is included, giving the integrator a status contact to wire back into a PLC input or indicator without sourcing a side-mounted aux block; zero auxiliary contacts are listed in the auxiliary-circuit count field, so the integral switch is the only one on the device. Operating ambient is -20 to +60 °C, transport and storage are -50 to +80 °C, maximum installation altitude is 2 000 m, and shock resistance is 25g / 11 ms — a robust industrial envelope that does not need derating in a normal factory-floor panel.
Panel-side mounting and wiring
The breaker snaps onto a 35 mm standard mounting rail per DIN EN 50022 with screw support, mounts in any position, and measures 45 mm wide, 96 mm deep, and 97 mm tall — a slim vertical profile that keeps DIN-rail real estate tight in multi-starter panels; front-of-panel touch protection is IP20. Main current terminals are screw-type and accept 2x (1... 2.5 mm²) plus 2x (2.5... 6 mm²) for solid, stranded, and finely stranded with ferrule conductors, with the AWG range of 2x (14... 10) covering the equivalent North American wire sizes.
Thermal budget inside the enclosure
Total power dissipation is 5.5 W in the hot operating state, or 1.8 W per pole, which enclosure thermal sizing must absorb per installed breaker.