What the ratings mean for fit
The S803C-D63 is a 3-pole miniature circuit breaker rated 63 A with a D trip curve. That D curve means it tolerates short-duration inrush currents 10 to 20 times the rated current before tripping — sized for motor and transformer loads where the startup surge would nuisance-trip a B or C curve breaker. The 15 kA interrupting capacity at 400 VAC tells you it can safely clear a fault up to that level without welding contacts or cascading failure upstream. On DC circuits it's rated 10 kA, so it works in DC distribution panels too, but verify the voltage matches your bus. Snaps onto standard DIN rail in the enclosure. Three poles switch all phases in a three-phase circuit with a single handle. The 230 VAC rating per pole covers line-to-neutral applications.