Motor protection circuit breaker for 400 V panels
The Siemens SIRIUS 3RV2021-0GA20 is a motor protection circuit breaker in size S0, designed for protecting motor branch circuits. It carries a Trip Class 10, meaning it will trip within 10 seconds at 7.2× the thermal setting — the standard for standard-duty induction motors driving pumps, fans, and conveyors. The 100 kA breaking capacity at 400 V AC means it can safely clear a fault up to that level without cascading upstream, so it's suitable for installation in high-fault-capacity distribution panels where the available short-circuit current is substantial.
What the ratings mean for panel fit
Width is 45 mm, depth 97 mm, height 119 mm. That 45 mm footprint is standard for S0 frame breakers — it occupies two 22.5 mm modular positions on the DIN rail. Mounting is screw and snap-on onto 35 mm DIN rail per DIN EN 60715, and the mounting position is any orientation. The spring-loaded terminals accept 2x (1 to 10 mm²) solid or stranded wire, which covers the typical motor power circuit up to around 4 mm² for a 0.1 kW motor at 230 V. Phase failure detection is built in — critical for three-phase motor protection where loss of one phase can cause single-phasing damage.