System protection breaker for 400 V motor branch circuits
The Siemens SIRIUS 3RV2021-4EA10-0DA0 is a Size S0 circuit breaker designed for system protection in motor branch circuits, rated with a breaking capacity of 55 kA at 400 V AC. That figure governs fault interruption at the panel's main voltage level — enough to coordinate with most downstream contactors and overload relays without cascading upstream. Trip Class 10 means it clears a stalled-rotor condition within 10 seconds at locked-rotor current, matching standard IEC motor starting profiles.
Mounting and panel fit
Mounts via screw and snap-on onto 35 mm DIN rail per DIN EN 60715. The 45 mm width fits a standard 45 mm module slot; depth of 97 mm leaves clearance behind the rail for wiring. Any mounting position is allowed, so it can go sideways in a shallow enclosure if needed. Terminal screws accept 2x (1–2.5 mm²) solid or stranded, or 2x (2.5–10 mm²) — covers most motor feeder sizes up to 10 mm².
Breaking capacity across voltage levels
The breaker's interrupting performance varies with system voltage: 100 kA at 240 V AC, 55 kA at 400 V AC, 10 kA at 500 V AC, and 4 kA at 690 V AC. For DC applications, it delivers 25 kA at 400 V, 5 kA at 500 V, and 2 kA at 690 V. The 400 V AC figure is the one most panel builders will size against for standard three-phase motor circuits in European and Asian installations.