The 5SL3663-7MB is a Siemens SENTRON miniature circuit breaker rated 63 A with a C tripping characteristic, breaking 4.5 kA at 400 V AC per EN 60898 and IEC 60947-2. The 3P+N configuration (four-pole width, 72 mm) switches all three phases and the neutral — critical for TN or TT systems where neutral isolation is required during a fault.
The 72 mm width (4 width units at 18 mm each) occupies four adjacent slots — plan for that footprint in your enclosure layout. Accepts conductors from 0.75 mm² up to 25 mm², which covers most branch-circuit wiring from 2.5 mm² lighting circuits up to 16 mm² subfeeds.
Coordination and selectivity
Rated 20,000 mechanical switching cycles typical — adequate for distribution duty where the breaker operates only under fault or maintenance isolation. The C-curve at 63 A coordinates well with downstream C-curve subcircuits up to about 20 A, provided the 4.5 kA fault level is not exceeded upstream. For higher prospective fault currents, a current-limiting upstream device (e.g., an NH fuse or an SENTRON 3VA molded-case breaker) is needed to keep the let-through energy within the 5SL3's 4.5 kA rating.