The Siemens 5SL4603-8 is a 4-pole (3P+N) SENTRON miniature circuit breaker with a D tripping characteristic, rated 3 A at 400 V AC and a 10 kA breaking capacity per EN 60898 and IEC 60947-2. That D-curve means it tolerates the high inrush of motor and transformer loads without nuisance tripping — the magnetic trip kicks in at 10–20× rated current, so it's the right choice for inductive circuits, not general lighting or resistive heaters. The 10 kA SCCR at 400 V tells you it can safely interrupt a fault up to that level without cascading upstream — coordination matters when you're protecting a distribution board feeding multiple motor starters.
Fit and integration
Snaps onto DIN rail; occupies 4 modular width units (72 mm wide). Depth is 76 mm, installation depth 70 mm — leaves clearance for wiring gutters in a standard 200 mm deep enclosure. Neutral conductor is switched (3P+N), so you get full isolation on all poles. Mounting position any, which helps when the panel layout is tight and you're rotating breakers to match busbar orientation. IP20 with connected conductors — fine inside a closed panel, not for wet environments.
Thermal derating and environment
Rated 3 A at 30 °C ambient; derates to 2.88 A at 40 °C and 2.69 A at 55 °C. If your panel runs hot — say a crowded MCC with drives below — the effective ampacity drops. The breaker is halogen-free and silicon-free, which matters for outgassing-sensitive environments like clean rooms or sealed enclosures near sensitive electronics. Temperature range -40 to 75 °C covers outdoor enclosures in cold climates. Sealable with a lockout provision for lockout/tagout compliance.