What it is and what it does
The Siemens SIRIUS 3RV1021-1GA10-0FJ0-ZX95 is a motor circuit breaker — a single device that combines a circuit breaker and a thermal-overload relay for motor protection. It is designed for screw-and-snap-on mounting onto 35 mm DIN rail per DIN EN 50022, which is the standard integration for industrial control panels. Rated continuous current is 6.3 A, and the breaking capacity reaches 100 kA at 400 V AC (also 100 kA at 240 V and 500 V AC). At 690 V AC the breaking capacity drops to 6 kA — the arc energy at higher voltage limits interruption. This means the part can safely clear a bolted fault up to 100 kA on a 400 V line without the arc flashing over or the device rupturing, which is critical for SCCR compliance in a panel feeding a motor branch circuit. Trip class is CLASS 10, so it will trip within 10 seconds at 7.2× the current setting — fast enough to protect a standard induction motor winding during a stall or locked-rotor event. Phase failure detection is built in, meaning if one phase drops out the breaker will trip on the resulting current imbalance before single-phasing damages the motor.
Where it goes and what it connects to
Mounts in any position on 35 mm DIN rail per DIN EN 50022, with zero required clearance at the sides or rear (0 mm backwards, 0 mm at the side). The 45 mm width means it occupies a single 45 mm slot in the panel — one standard unit on the rail. Panel depth allowance must accommodate the 96 mm body depth plus wiring bend radius. Main circuit terminals are screw-type, accepting solid or stranded conductors: 2×(1…2.5 mm²) and 2×(2.5…6 mm²), or AWG 14…10. The terminal block is rated for the full 6.3 A continuous current and the 100 kA breaking capacity — no separate fuse or supplementary protection is required upstream when the available fault current stays within the 100 kA rating. Power dissipation at rated current in hot operating state is 7.25 W total, 2.4 W per pole — enough heat to consider in a tightly packed panel with adjacent devices. Front face carries IP20 touch-safe protection; the busbar and live terminals behind the cover are not finger-safe until the cover is installed. No auxiliary contacts are included (0 auxiliary contacts), so any remote status signaling requires a separate auxiliary switch block snapped onto the side.
Environment and durability
Operating temperature range is -20 to +60 °C, storage and transport -50 to +80 °C. The 25g / 11 ms shock resistance covers most industrial vibration and occasional mechanical impact during transport or panel door slam. Maximum operating altitude is 2 000 m without derating — above that, air density drops and arc quenching performance degrades, so the breaking capacity must be reduced per IEC 60947-2. Mechanical endurance of the main contacts is typically 100 000 operations; the maximum switching rate at AC-3 duty is 15 operations per hour. For a motor starting once every few minutes on a conveyor or pump, that rate is not a constraint — it only matters for high-cycle applications like rapid reversing or jogging.