Motor protection circuit breaker, size S0 — 100 kA SCCR at 400 V
The Siemens SIRIUS 3RV2021-1KA20-0BA0 is a motor protection circuit breaker in the S0 frame size, designed for the main current circuit of a motor branch. Its headline rating is a 100 kA short-circuit breaking capacity at 400 V AC — meaning it can safely interrupt a fault current up to that level without upstream fuses needing to clear first, which simplifies panel coordination and lets you size the feeder breaker closer to the load. At 500 V the SCCR holds at 42 kA, and at 690 V it is 4 kA (AC) or 6 kA (AC depending on the cited entry), so the part is best deployed on 400 V or 480 V systems where its full interrupting capability is available. Trip Class 10 means the bimetal trip element will open within 10 seconds at 7.2× the thermal setting — the standard for protecting standard induction motors during a locked-rotor event. Phase failure detection is built in, so a lost phase on the line side will trip the breaker rather than letting the motor single-phase and overheat. The part mounts on 35 mm DIN rail per DIN EN 60715, with screw-and-snap-on fastening, and can be oriented in any position.
Termination and panel integration
The main current circuit terminates via spring-loaded terminals, accepting 2 × (1 to 10 mm²) solid or stranded wire. The S0 frame occupies 45 mm width on the DIN rail, with a depth of 97 mm and height of 119 mm. Clearance requirements: 50 mm above and below, 30 mm to the side, zero forward or backward — so it fits tightly against a back panel or enclosure wall. The screwdriver shaft for the terminal clamps is 3 mm diameter, tip size 3.0 × 0.5 mm.