Motor protection circuit breaker for the panel builder
The Siemens SIRIUS 3RV1021-4DA10 is a motor protection circuit breaker rated for 25 A continuous current and 11 kW at 400 V AC. Its Class 10 trip characteristic means it clears a stalled-rotor condition fast enough to protect standard induction motors during start-up — the thermal memory tracks winding heating between starts. Phase failure detection is built in, so a lost phase on the line side trips the breaker before single-phasing cooks the motor. The 50 kA breaking capacity at 400 V AC gives it enough interrupting rating for most industrial distribution panels without needing a current-limiting upstream fuse for SCCR compliance.
Breaking capacity across the voltage range
The 3RV1021-4DA10's breaking capacity drops as line voltage rises: 100 kA at 240 V AC, 50 kA at 400 V AC, 10 kA at 500 V AC, and 4 kA at 690 V AC. At 690 V the 4 kA figure governs — if your panel's available fault current exceeds that, you need an upstream current-limiting device or a higher-rated frame. The 6 kV rated surge voltage withstand means the breaker handles switching transients on motor circuits without internal flashover.
Mounting and wiring
Mounts via screw or snap-on onto 35 mm DIN rail per DIN EN 50022. The 45 mm width fits standard SIRIUS spacing alongside contactors and overloads. Screw-type terminals on both main and auxiliary circuits accept solid or stranded conductors: 2x (1…2.5 mm²) or 2x (2.5…6 mm²), with AWG equivalents 2x (14…10). No backward or side clearance is required, so you can butt it against adjacent devices on the rail. IP20 on the front means the busbars are touch-safe in an enclosed panel; the interior of the cabinet provides the rest of the protection.
Thermal and environmental limits
Operating ambient temperature range is -20 to +60 °C; storage and transport extend to -50 to +80 °C. The 25g / 11 ms shock rating means it survives the vibration and impact typical of machine-mounted panels. Power dissipation at rated current is 10.5 W total, 3.5 W per pole — factor that into enclosure thermal calculations if you're packing several breakers in a small cabinet. Maximum operating frequency is 15 switching cycles per hour in AC-3 duty, which covers normal motor start-stop sequences but not rapid cycling.