SIRIUS 3RV2021-4CA10-0BA0 — motor protection circuit breaker, S0 frame
The Siemens SIRIUS 3RV2021-4CA10-0BA0 is a motor protection circuit breaker in the S0 frame size, designed for protecting three-phase induction motors against overload, short-circuit, and phase failure. It is rated for Trip Class 10, meaning it will trip within 10 seconds at 7.2× the thermal setting — fast enough to protect standard IEC motors during a locked-rotor event. The breaker mounts via screw and snap-on onto a 35 mm DIN rail per DIN EN 60715, and its 45 mm width means it occupies a single modular slot in a panel, leaving room for contactors and auxiliaries on the same rail. Rated motor power at 230 V is 5.5 kW, and the breaker carries a short-circuit breaking capacity of 25 kA at 400 V AC. That 25 kA figure is the SCCR at the load side terminals — sufficient for most industrial distribution panels with a transformer upstream. For higher fault levels, the breaker coordinates with upstream fuses: the evidence specifies gG 63 A at 400 V, gG 50 A at 500 V, and gG 50 A at 690 V as maximum back-up fuse ratings. Phase failure detection is built in, so the breaker will trip if one phase drops out — a common cause of single-phasing motor burnout in field applications. Ground fault detection is not included, so for sensitive earth-leakage protection, a separate residual current device is needed downstream.
Panel integration and mounting
The 3RV2021-4CA10-0BA0 snaps onto a 35 mm DIN rail (DIN EN 60715) and can be mounted in any position. Its footprint is 45 mm wide × 97 mm high × 97 mm deep, with clearance requirements of 50 mm upward and downward, 30 mm to the side, and zero clearance forward or backward. That zero forward clearance means it can be mounted flush against a gland plate or back panel without derating — useful for tight enclosures. The screw-type terminals on the main current circuit accept 2× (1 to 2.5 mm²) or 2× (2.5 to 10 mm²) solid or stranded copper, terminated with a Pozidriv size 2 screwdriver tip (shaft diameter 5 to 6 mm).