What it is and what it does
The Siemens SIRIUS 3RV2021-1HA10-ZW97 is a motor protection circuit breaker designed for motor protection, with a Trip Class 10 rating that matches standard induction motor starting profiles — it allows the motor to draw locked-rotor current for up to 10 seconds before tripping, so it won't nuisance-trip on a normal start but still protects against a stalled rotor. It mounts via screw and snap-on onto 35 mm DIN rail per DIN EN 60715, in any mounting position, and uses screw-type terminals for the main current circuit — accept 2x (1–2.5 mm²) or 2x (2.5–10 mm²) solid or stranded wire. Rated breaking capacity hits 100 kA at both 240 V and 400 V AC, so it can safely interrupt high fault currents on industrial distribution without needing an upstream current-limiting fuse in most panels.
Key ratings and what they mean for fit
Phase failure detection is built in — if one phase drops out, the breaker trips to prevent single-phasing damage to the motor. Ground fault detection is not included, so if that's required, an external ground-fault relay or a different variant is needed. Operating temperature range is -20 to +60 °C; storage and transport range is -50 to +80 °C. The 45 mm width and 97 mm depth fit standard motor starter combos on DIN rail — the 45 mm footprint leaves room for a contactor and overload block in a typical panel layout. Rated operational voltage covers 20 to 690 V, and at 480 V the continuous current rating is 8 A; at 600 V also 8 A; at 690 V the breaking capacity drops to 4 kA — so for 690 V systems, verify the available fault current stays under that limit.