Motor protection circuit breaker, size S0, Class 10, 6.3 A AC-3
The Siemens SIRIUS 3RV2021-1GA20-0BA0 is a motor protection circuit breaker designed for the main current circuit of three-phase motors. It is part of the SIRIUS family and comes in the compact S0 frame size (45 mm wide, 97 mm deep, 119 mm high). The breaker is rated for AC-3 duty at 6.3 A at 400 V, with a trip class of CLASS 10, meaning it will trip within 10 seconds at 7.2× the thermal setting — fast enough to protect standard induction motors during locked-rotor conditions. Breaking capacity is 100 kA at 240 V, 400 V, and 500 V AC, dropping to 6 kA at 690 V AC. That 100 kA figure at 400 V means it can safely interrupt a fault current up to 100,000 amps without welding contacts or cascading failure upstream — critical for panels with high available fault current from large transformers. Phase failure detection is built in, so if one phase drops out, the breaker trips before single-phasing cooks the motor. No ground fault detection on this variant.
Mounting and wiring
Mounts via screw and snap-on onto 35 mm standard mounting rail per DIN EN 60715. Any mounting position is allowed. The main current circuit uses spring-loaded terminals accepting 2× (1–10 mm²) solid or stranded wire. That spring-cage design speeds up panel wiring — no screw torque to check, just strip and push. Clearance distances: 50 mm upwards and downwards, 30 mm to the side, zero forwards or backwards. That 50 mm top clearance is the one to watch when stacking breakers in a row — leave room for the arc chute to vent.