The Siemens 5SY4663-5 is a SENTRON miniature circuit breaker with a 4-pole 3P+N design, rated 63 A at 35 °C. The tripping characteristic A means it reacts to very short overcurrents — typically used for semiconductor protection or long cable runs where you need fast clearing on small overloads, not motor starting. For DC circuits, it's rated 15 kA per IEC 60947-2 as well.
Derating and ambient conditions — the real-world current
The 63 A rating holds at 35 °C. Above that, the breaker derates: 59.98 A at 40 °C, 58.4 A at 45 °C, 56.83 A at 50 °C, 55.12 A at 55 °C, and 53.42 A at 60 °C. If your enclosure runs hot — say 50 °C internal ambient — you're effectively working with a 56.83 A device, not 63 A. The operating temperature range is -40 °C to 75 °C, with humidity limits: max 95% up to 55 °C, then dropping to 35% at 75 °C. Overvoltage category III suits fixed installations like distribution boards.
The combined terminal design (top and bottom) accepts conductors without needing separate busbar adapters for most panel layouts. Touch protection is built in. Sealable, halogen-free, silicon-free — relevant for environments where outgassing or contamination matters (clean rooms, food processing).