The Siemens 3RV2431-4VA10 is a SIRIUS-brand circuit breaker designed specifically for transformer protection — not a general-purpose motor protective breaker. That distinction matters when you're coordinating upstream and downstream devices on a transformer secondary. Trip Class 10 trips within 10 seconds at the thermal setting.
At 55 mm wide and 149 mm deep, it fits a standard enclosure row. Screw terminals on the main circuit accept 2× (1–35 mm²) or 1× (1–50 mm²) solid or stranded copper. The M6 terminal studs are sized for the transformer-side cable, not just the load side — common oversight when landing a 50 mm² primary feed. That 10 mm side gap is tighter than many general-purpose breakers, so check adjacent device spacing before laying out the DIN rail.