What it is and what it does
The Siemens 3RV1021-0KA15-ZX95 is a SIRIUS motor protection circuit breaker designed for motor protection, rated at 1.25 A continuous current with a Class 10 trip characteristic — meaning it will trip within 10 seconds at 7.2× the thermal setting, fast enough to protect standard induction motors during a locked-rotor event without nuisance tripping on normal starts. It carries a 100 kA breaking capacity at 400 V AC (and at 240 V, 500 V, and 690 V as well), so it can safely interrupt fault currents up to that level without upstream fuses or a larger breaker — a real space saver in a crowded panel. The auxiliary switch is transverse design and the product extension for an auxiliary switch is available, so you can add a remote status contact without changing the breaker footprint.
Mounting and integration
Snaps onto 35 mm DIN rail per DIN EN 50022, screw and snap-on mounting, any position. The 45 mm width and 97 mm height fit a standard 4-module slot; depth is 96 mm, so check your enclosure depth if you're retrofitting into a shallow gland plate. Main circuit terminals accept solid 2x (0.5…1.5 mm²) and 2x (0.75…2.5 mm²), stranded 2x (1…2.5 mm²) and 2x (2.5…6 mm²), or AWG 2x (14…10). Auxiliary and control circuit terminals are also screw-type, same wire ranges. IP20 front protection — fine for a closed panel; not rated for washdown or outdoor exposure without an enclosure.
Lifecycle and sourcing
RoHS compliance date is 01.05.2012, meaning it meets the EU RoHS directive as of that date. No REACH or UL listing is explicitly stated in the evidence, but the SIRIUS series typically carries UL/CSA certification — confirm with your compliance team if your BOM requires a specific cert number.