Motor Protection Circuit Breaker, 1 A, Class 10 — SIRIUS 3RV1021-0JA10
The Siemens SIRIUS 3RV1021-0JA10 is a motor protection circuit breaker rated for 1 A continuous current, with a Class 10 trip characteristic designed to protect motors during starting without nuisance tripping. It mounts on a 35 mm DIN rail per DIN EN 50022 and occupies a 45 mm wide slot — standard panel footprint, no surprises. Breaking capacity is 100 kA across the board at 240 V, 400 V, 500 V, and 690 V AC — that's full-range fault clearing without cascading upstream breakers. For a 1 A motor protector, that's serious headroom; it handles high-fault-current panels without coordination gymnastics. Phase failure detection is built in, so a lost phase trips the breaker before the motor cooks. Ground fault detection is not included — if you need that, this isn't the variant.
What the Ratings Mean for Your Panel
At 400 V, the 3RV1021-0JA10 is rated for 0.25 kW motor load. That's a small motor — think a coolant pump, a fan, or a small conveyor drive. The Class 10 trip means it will hold through a typical motor start without tripping, but clears quickly on a locked-rotor condition. Screw terminals on both main and auxiliary circuits accept solid or stranded wire: 2x (1…2.5 mm²) and 2x (2.5…6 mm²) per clamp. That's enough for the motor leads and control wiring. AWG equivalent is 2x (14…10). No special tools beyond a screwdriver. Power dissipation is 7.25 W total in hot operating state, or 2.4 W per pole. In a crowded panel with multiple breakers side by side, that heat adds up — factor it into your thermal budget. IP20 on the front means it's protected against finger contact but not washdown. Rated for 15 operations per hour at AC-3 — this is a motor starter duty cycle, not a high-speed switching device. Shock rated at 25g / 11 ms, good for industrial machinery and conveyors.