What this 63 A B-curve MCB does on the rail
The ABB S204-B63 is a 4-pole miniature circuit breaker rated 63 A with Trip Curve B, meaning its magnetic trip operates at 3 to 5 times the rated current — fast enough to clear a hard short in a cable run but tolerant of inrush from resistive loads like heaters or lighting banks. DIN-rail mount snaps into any standard panel enclosure; the four poles let you switch all three phases plus neutral in a single module.