Siemens 5SY5263-6 — 63 A B-curve MCB for panel and load protection
The Siemens 5SY5263-6 is a 2-pole miniature circuit breaker from the SENTRON family, rated 63 A at 35 °C with a B tripping characteristic and a 10 kA breaking capacity per IEC/EN 60898-2 and UL1077. It also carries a 10 kA DC rating per EN 60898-2 at 440 V DC, making it suitable for universal-current applications where AC or DC loads need overcurrent protection in a single device.
At 63 A, this breaker handles main feeder or large branch circuits in distribution boards. The 440 V DC rating (10 kA) covers DC bus or battery-backed circuits, though polarity must be observed on the supply side. Thermal derating is published: 63 A at 35 °C, 59.16 A at 40 °C, 57.14 A at 45 °C, 55.06 A at 50 °C, 52.92 A at 55 °C, and 50.65 A at 60 °C.
Mounting position is unrestricted — vertical, horizontal, or inverted. The breaker is sealable for anti-tamper requirements. Halogen-free and silicon-free construction supports use in clean environments or where outgassing must be minimized.