The Siemens 5SJ6463-6RC is a 4-pole miniature circuit breaker (MCB) from the Retail line, rated at 63 A with a B tripping characteristic and a 6 kA breaking capacity. It is designed for overcurrent and short-circuit protection in final distribution circuits, typically snapped onto a DIN rail inside a consumer unit or panelboard.
The 63 A rating at 6 kA breaking capacity means this MCB can safely interrupt a fault current up to 6,000 A without welding its contacts or failing catastrophically — sufficient for most residential and light commercial panelboards where the prospective short-circuit current stays under that threshold. The B characteristic (instantaneous trip at 3–5× In, i.e., 189–315 A) is the standard choice for resistive loads like heaters, lighting, and general socket outlets; it avoids nuisance tripping on small motor or transformer inrush that a C-curve would handle better. Four poles let it switch all three phases plus neutral in a three-phase distribution board, or serve as a double-pole + double-pole in a split-phase configuration.