Motor protection breaker built for the grit and heat
The Siemens 3RV1021-1DA15-ZX95 is a SIRIUS motor protection circuit breaker rated for a continuous current of 3.2 A with a Class 10 trip characteristic, meaning it clears overloads fast enough to protect standard induction motors during start-up without nuisance tripping. Phase failure detection is built in — if one leg drops, the breaker opens before single-phasing cooks the winding. The 100 kA breaking capacity at 400 V AC gives it the interrupting muscle to handle high-fault panels without cascading upstream. It snaps onto a 35 mm DIN rail per EN 50022 and can mount in any position, which simplifies panel layout when you're squeezing gear into a crowded enclosure.
What the ratings mean for a dusty panel
Operating temperature spans -20 to +60 °C, so it survives a hot control room next to a kiln or a compressor shed in summer. The IP20 front keeps accidental finger contact out but is not sealed against dust ingress — mount it inside a cabinet that handles the environment. Screw terminals on both the main and auxiliary circuits accept solid conductors from 0.5 to 1.5 mm² and stranded up to 6 mm², which covers most motor feeder wiring. At 45 mm wide and 97 mm tall, it occupies a single modular space on the rail — plan your fill factor accordingly.
Auxiliary switch and wiring notes
The breaker supports an auxiliary switch with a transverse design, which means the contacts open sideways — useful for signaling the PLC or safety relay that the breaker has tripped. The auxiliary contacts are rated 1 A at 24 V, 0.5 A at 230 V, and 0.15 A at 60 V. That 24 V rating covers most PLC input cards; the 230 V rating handles control transformers. Keep the switching frequency at AC-3 duty to a maximum of 15 operations per hour — this is a protection device, not a cycled contactor.