The Siemens 5SL6663-8CC is a 3+N-pole miniature circuit breaker rated 63 A with a D tripping curve, 400 V, and a 6 kA breaking capacity. It sits in the Basic Devices family — the workhorse MCB line for DIN-rail panels where you need a D-curve to handle high inrush loads like motor starters or transformer primaries without nuisance tripping on the magnetizing surge.
RoHS compliant since 01-06-13, with REACH candidate-list disclosure available on request.
The D-curve (10-20x In) is the key spec for procurement: it's sized for loads that slam the breaker with a short inrush — think motor contactor coils, solenoid banks, or control transformers. A C-curve would trip on that first surge; the D holds through it. Three poles plus a switched neutral (3+N) means you get full isolation on all four conductors — useful where you need to lock out the neutral for safe downstream work.
The 3+N package takes four module widths — plan your enclosure fill accordingly. Spring-cage or screw terminals accept 0.75–25 mm² conductors depending on the terminal variant on this specific order code; verify the termination type on the nameplate before wiring.