The ABB S204-D63 is a 4-pole miniature circuit breaker with a D trip curve, rated 63 A at 277 VAC and a 10 kA interrupting capacity. The 63 A rating and 4-pole configuration suit three-phase loads with a switched neutral, common in European-style distribution panels. DIN-rail mounting means it clips directly into a standard 35 mm rail inside the enclosure — no panel cutting or busbar drilling needed.
In a selectivity study, the D curve's higher magnetic threshold gives it better discrimination against downstream C-curve MCBs on motor-starting circuits — the downstream breaker trips first on the inrush, leaving this one closed to serve the rest of the panel.