The 5SY4305-8 carries a D tripping characteristic — magnetic trip threshold is 10–20× In, so it holds through the inrush of motor starters, solenoid valves, and small transformers without nuisance tripping on the start. At 0.5 A rated current, this breaker is sized for control-circuit protection, not main feeder duty. At 400 V AC this breaker clears a 35 kA prospective fault without cascading upstream, which gives the panel designer headroom for a high-fault utility feed.
DIN-rail fit and thermal derating
Width is 54 mm, which is 3 modular units on a standard DIN rail. Depth 76 mm, height 90 mm — leaves clearance for gland plates and wiring ducts. Mounting position is any; the quick-assembly system clips onto the rail without tools. Rated current is temperature-dependent: 0.5 A at 35 °C, derated to 0.48 A at 40 °C, 0.46 A at 45 °C, 0.45 A at 50 °C, 0.44 A at 55 °C, and 0.42 A at 60 °C. For a 40 °C panel interior — typical for a sealed enclosure with drives — budget the 0.48 A ceiling. The ambient humidity limits are 95 % up to 55 °C, tapering to 35 % at 75 °C.