What this breaker does on a motor branch
The Siemens 3RV1042-4DA10 is a SIRIUS motor protection circuit breaker rated for 25 A continuous current and 11 kW at 400 V AC-3 duty. Three poles, screw-type box terminals on the main circuit, and an integrated phase-failure detection that trips if one phase drops out — a common failure mode that single-phases a motor and cooks it fast. No ground-fault detection on this variant, so if you need that, look at the GF versions in the same family.
The interrupting rating drops as voltage climbs: 100 kA at 240 V and 400 V, 30 kA at 500 V, 12 kA at 690 V. At 690 V you're into the 12 kA range — still adequate for most 690 V industrial grids, but worth checking against the transformer impedance and cable length on your specific line.
Accepts solid conductors 2x (2.5 … 16 mm²) and stranded up to 1x (10 … 70 mm²). Depth is 174 mm, width 70 mm, height 165 mm — fits a standard 8-module-wide slot on most DIN assemblies. Mounting position any, so vertical or horizontal busbars are fine.