SIRIUS motor protection circuit breaker, 12.5 A, CLASS 10
The Siemens 3RV1021-1KA38-1KT1 is a SIRIUS motor protection circuit breaker rated for 12.5 A continuous current with a CLASS 10 trip characteristic. Rated breaking capacity hits 100 kA at 400 V AC, so it can interrupt high fault currents typical in industrial distribution without needing an upstream current-limiting fuse for most installations. Built-in phase failure detection ensures the breaker trips if one phase drops out — critical for preventing single-phasing damage on three-phase motor loads.
Breaking capacity and selectivity
At 400 V AC the 3RV1021-1KA38-1KT1 delivers 100 kA breaking capacity, matching the 3RV1011-1HA10's 100 kA at 400 V — so in a panel originally specified around the 1HA10, this unit drops into the same fault-current coordination zone without recalculating arc-flash limits. At 690 V AC the rating drops to 6 kA; if your line runs at 690 V, verify the available fault current stays under that ceiling.
Mounting and panel integration
Mounts via screw or snap-on onto 35 mm DIN rail per EN 50022. Width is 45 mm — one standard module — so it fits a 9-module row with room for a contactor and overload alongside. Screw-type terminals on the main circuit accept 2x (0.25…2.5 mm²) solid or 2x (24…14 AWG) stranded. The auxiliary switch is transverse-mounted and included as standard. IP20 on the front face; no washdown rating — keep it inside the enclosure, not on the machine frame.