Siemens 5SP4391-8 — 100 A D-curve MCB for high-inrush loads
The Siemens 5SP4391-8 is a SENTRON miniature circuit breaker with a D tripping characteristic, rated 100 A at 400 V AC and 50/60 Hz. For a panel fed from a transformer with a high prospective short-circuit current, this rating governs whether the MCB coordinates with the upstream fuse or breaker. Three-pole construction (3P) with a width of 4.5 modular units (81 mm). Mounts on DIN rail or via screw fixing in any orientation — no derating for horizontal installation.
Rated 100 A at 30 °C ambient, it derates to 95 A at 40 °C, 92 A at 45 °C, 89.5 A at 50 °C, 87 A at 55 °C, and 84 A at 60 °C. In a sealed, high-density panel at 50 °C, the usable current is about 10 % below the nameplate — plan the load circuit accordingly.
Part of the Siemens SENTRON 5SP series, halogen-free and silicon-free, with tunnel terminals top and bottom for stranded or solid conductors.
The 4.5 MW width (81 mm) occupies a standard DIN-rail slot; tunnel terminals accept conductors without ferrules for quick wiring. Sealable cover is standard for lockout/tagout compliance. IP20 with connected conductors;