What the ratings mean for fit
The Siemens 3RV1021-1KA10-ZW98 is a SIRIUS motor protection circuit breaker rated for 12.5 A continuous current with a CLASS 10 trip characteristic — meaning it clears overloads fast enough to protect a motor winding during a locked-rotor event without nuisance tripping on startup inrush. The 100 kA breaking capacity at 400 V AC means it safely interrupts fault currents up to that level without cascading upstream; at 690 V the breaking capacity drops to 6 kA, so verify the available fault current at the installation point. Phase failure detection is built in, which protects three-phase motors from single-phasing damage.
Mounting and integration
Snap-on mounting onto 35 mm DIN rail per DIN EN 50022 — no tools needed for rail attachment, but screw-type terminals for both main and auxiliary/control circuits require a screwdriver for wiring. Accepts solid or stranded conductors: 2x (1... 2.5 mm²) and 2x (2.5... 6 mm²) per terminal. Zero clearance needed at the back or sides, so it packs tight in a dense panel. IP20 on the front means finger-safe but not washdown-rated.