DC rating and thermal derating
Rated 0.5 A at 35 °C ambient, the 5SY5105-7CC12 derates to 0.46 A at 40 °C, 0.44 A at 45 °C, 0.42 A at 50 °C, 0.4 A at 55 °C, and 0.38 A at 60 °C. That thermal curve governs the real continuous load in a sealed enclosure — if the panel ambient sits at 50 °C, the breaker can only carry 0.42 A continuously without nuisance tripping.
Railway certification and environmental tolerance
Explicitly designed for railway operation, with a wide ambient range from -40 °C to 75 °C and humidity tolerance up to 95% at 55 °C, 55% at 70 °C, and 35% at 75 °C. IP20 with connected conductors — finger-safe on the front, but the terminals require enclosure protection.
Mechanical fit and panel integration
Depth is 76 mm (70 mm installation depth), height 90 mm. Sealable and halogen-free / silicon-free — no outgassing concerns in sealed enclosures. Combined top and bottom terminals simplify daisy-chaining; note the polarity requirement on the DC supply. Supplementary devices (auxiliary contacts, shunt trip, alarm switch) can be installed on the right side.