The Siemens 5SY8163-8 is a 1-pole SENTRON miniature circuit breaker with a D tripping characteristic, rated 63 A at 45 °C and delivering a 20 kA breaking capacity at 440 V AC per IEC 60947-2.
Panel fit and environmental tolerance
Mounting position is any, so horizontal or vertical busbar arrangements are fine. Ambient range spans -40 °C to 75 °C, with derating above 45 °C: 63 A at 45 °C, 61.05 A at 50 °C, 59.03 A at 55 °C.
The D characteristic (10–20× In magnetic trip) is the key differentiator here. Where a C curve (5–10× In) would nuisance-trip on a motor start or a welding transformer inrush, the D curve holds. Pair it with loads that have a high ratio of starting to running current — small motors, pumps, compressors, or industrial machinery with short-duration inrush. The 63 A rating at 45 °C covers a 3-phase motor up to roughly 30 kW at 400 V, but always confirm the full-load current against the derated value at your panel ambient. Breaking capacity is 20 kA at 440 V AC per IEC 60947-2, and 15 kA at DC up to 72 V. The DC rating (15 kA at 72 V) covers control-circuit or battery-backed loads, but note it's a single-pole break — no neutral switching.