The Siemens SENTRON 5SY8250-8BB08 is a 2-pole miniature circuit breaker rated 50 A with a D tripping characteristic and a 20 kA breaking capacity at 400 V AC per IEC 60947-2. It uses only magnetic tripping — no thermal bimetal — so it's built for loads with high inrush, like motor starters or transformers, where a standard B- or C-curve would nuisance-trip on startup.
The D-curve (10–20× In magnetic trip) handles motor inrush that can hit 8–12× FLA for 100–200 ms; a C-curve (5–10× In) would trip on that same transient. Ambient temperature range is -40 to 75 °C, with derating for humidity (95% at 55 °C, down to 35% at 75 °C). Siemens lists it for mechanical engineering and industry applications — think machine tool cabinets, conveyor drive panels, or pump control stations where a magnetic-only breaker gives fast, repeatable short-circuit protection without thermal drift.