The Siemens 5SY3163-6 is a 1-pole miniature circuit breaker from the SENTRON 5SY3 family, rated 63 A at 400 V AC with a B tripping characteristic. For a 63 A single-pole MCB, that covers lighting, heater banks, and small transformer primaries.
Breaking capacity — the number that decides coordination
Rated 4.5 kA per EN 60898 and 6 kA per IEC 60947-2 at 400 V AC. For DC circuits, it handles 15 kA per IEC 60947-2 up to 72 V, and it carries a 5 kA rating under UL 1077 and CSA C22.2 No.235. That 6 kA IEC rating puts it in the standard industrial range — adequate for most sub-distribution boards fed from a transformer or main breaker. If your available fault current exceeds 6 kA, you need an upstream current-limiting device or a higher-rated MCB.
Installation depth is 70 mm (the overall depth is 76 mm, which includes the toggle). Sealable, touch-protected, IP20 with conductors connected.