D-curve trip for high-inrush loads
The Siemens 5SY4105-8 is a SENTRON miniature circuit breaker with a D tripping characteristic, meaning it tolerates the high inrush currents typical of motor starters, transformers, and welding equipment without nuisance tripping — the magnetic release kicks in at 10–20× rated current, not the 5–10× of a C-curve. Single-pole construction (1 MW width, 18 mm) handles 400 V AC line-to-neutral circuits. At DC per IEC 60947-2 it's rated 15 kA. UL 1077 recognized at 5 kA, so it fits North American supplementary protection applications.
Panel fit and environmental tolerance
Mounting position any orientation. Pollution degree 3 (conductive or dry non-conductive pollution — typical in industrial control rooms). Vibration resistance per IEC 60068-2-6: ±1 mm at 5–25 Hz, 50 m/s² at 25–150 Hz. IP20 with conductors connected — protected against finger contact, not washdown.