The Siemens 3RV5431-4DA10 is a SIRIUS-brand circuit breaker specifically designed for transformer protection, not general motor starting. It's a 3-pole, size S2 unit rated at 25 A continuous (AC-3 duty at 400 V) with a Class 10 thermal overload release and a magnetic short-circuit trip. The screw-type box terminals accept up to 35 mm² (1x) or 25 mm² (2x) solid/stranded copper, and it mounts on a standard 35 mm DIN rail per EN 50022. The magnetic short-circuit trip handles the high fault currents. Rated operational voltage goes up to 690 V AC-3, and it's good for 50/60 Hz systems. Power dissipation is 12 W typical at full load.
Depth is 149 mm from the rail face, width 55 mm, height 140 mm. The terminals are at top and bottom, which is standard for a panel layout. Torque the main contact screws to 3–4.5 N·m.