What this part is and what it does
The Siemens SIRIUS 3RV1021-1HA15-ZX95 is a motor protection circuit breaker — the component that sits between the contactor and the motor in a standard motor feeder. Its job is to protect the motor against overload (via the thermal bimetal strip) and short-circuit (via the magnetic trip), and it does both in one compact 45 mm wide package that snaps onto a 35 mm DIN rail per DIN EN 50022. Rated for a continuous current of 8 A, it covers a 3 kW motor at 400 V AC. The Trip Class 10 means it will trip within 10 seconds at 7.2× the set current — standard for standard-duty motor starting where the inrush duration is short. Breaking capacity is substantial: 100 kA at 240 V and 400 V AC, 42 kA at 500 V, and 6 kA at 690 V. That 100 kA at 400 V means it can interrupt a fault current up to that level without the upstream breaker needing to clear the fault — important for selectivity in a distribution panel.
Key features for the panel builder
Mounts in any position, screw or snap-on onto 35 mm DIN rail. Dimensions are 45 mm wide × 97 mm high × 96 mm deep — fits a standard 45 mm slot in a motor control center bucket. Screw-type terminals on both main and auxiliary/control circuits. Solid wire capacity: 2×(0.5…1.5 mm²) and 2×(0.75…2.5 mm²). Stranded: 2×(1…2.5 mm²) and 2×(2.5…6 mm²). AWG equivalent for main contacts: 2×(14…10). Zero clearance required at the back or sides — 0 mm spacing — so it packs tight against adjacent devices. IP20 protection on the front — finger-safe when installed in an enclosure, but not washdown-rated. Operating temperature range is -20 to +60 °C; storage and transport from -50 to +80 °C.
Lifecycle and sourcing reality
It includes phase failure detection (trips on loss of one phase) but no ground fault detection. The auxiliary switch is a transverse design and the product extension for an auxiliary switch is available — the kit includes the provision, but the switch itself is ordered separately. RoHS compliance date is 01.05.2012 — the substance prohibition date marks the transition to RoHS-compliant production. No UL or CSA listing is explicitly stated in the spec record, but the SIRIUS family typically carries IEC certification for global panel builds.