What it is and what it does
The Siemens SIRIUS 3RV1021-1HA15-ZW97 is a motor protection circuit breaker rated for 8 A continuous current and 3 kW at 400 V, with a Class 10 trip characteristic — meaning it clears overloads fast enough to protect standard induction motors during stall or jam conditions without nuisance tripping on normal starts. Breaking capacity reaches 100 kA at 240 V and 400 V AC, dropping to 42 kA at 500 V and 6 kA at 690 V — enough for most industrial panel fault levels, but verify the available fault current at your service voltage.
Mounting and wiring
Snaps onto 35 mm DIN rail per EN 50022, occupies 45 mm width, and can be mounted in any position — useful when panel space is tight and you're stacking breakers vertically. Screw-type terminals on main and auxiliary circuits accept solid conductors from 0.5 mm² to 1.5 mm² (two per clamp) and stranded from 1 mm² to 6 mm² (two per clamp); AWG equivalents are 14–10 for the main contacts. Power dissipation in hot operating state is 9.25 W — factor that into enclosure thermal calculations, especially if the breaker is grouped with other heat sources.