SENTRON 5SY7105-7CC — 0.5 A C-curve MCB for tightly coupled protection
The Siemens SENTRON 5SY7105-7CC is a 1-pole miniature circuit breaker with a C-curve tripping characteristic, rated 0.5 A at 35 °C and 440 VAC single-phase. Breaking capacity is 50 kA per IEC 60947-2 at 440 VAC — that's a serious fault-current rating for a 0.5 A device, meaning it can safely interrupt a bolted fault up to 50 kA without welding contacts or rupturing the case. This matters in high-available-fault-current panels (close to a transformer or generator bus) where a standard 10 kA or 15 kA MCB would be undersized.
Thermal derating — don't let the 0.5 A nameplate fool you above 35 °C
The 0.5 A rating is only valid at 35 °C ambient. At 40 °C it derates to 0.44 A, at 45 °C to 0.41 A, at 50 °C to 0.38 A, and at 55 °C to 0.35 A. The maximum operating ambient is 75 °C, minimum -40 °C. IP20 with connected conductors — fine for a clean panel, not for washdown.