What this 100 A D-curve MCB is for
The Siemens 5SP4491-8 is a 4-pole miniature circuit breaker from the SENTRON 5SP4 series, rated 100 A with a D tripping characteristic. It breaks fault currents up to 10 kA per EN 60898 at 400 V AC, 50/60 Hz. The D-curve (10–20× In) is designed for loads with high inrush currents — motor starters, transformers, welding equipment — where a B or C curve would nuisance-trip on startup. Four poles let it switch three-phase plus neutral in a single module, saving panel width compared to ganging single-pole breakers. The 6-module-width footprint (108 mm) and 70 mm installation depth fit standard DIN-rail enclosures.
Key ratings and what they mean for fit
The 10 kA breaking capacity (per EN 60898) is the maximum prospective fault current the breaker can safely interrupt at 400 V AC. For industrial panels fed from a transformer with a short-circuit rating above 10 kA, you need upstream current-limiting fuses or a higher-rated MCCB — this MCB is sized for sub-distribution boards where the available fault current is known to be ≤10 kA. Overvoltage category III and pollution degree 3 mean the breaker is rated for fixed installations inside the distribution board — not for outdoor or wet locations without additional enclosure. The IP20 rating with connected conductors (IP40 at the handle with a distribution cover) confirms it is intended for enclosed panel mounting, not open-air use. The D-curve characteristic (10–20× In) means the magnetic trip activates between 1000 A and 2000 A for this 100 A unit. That delay allows motor-starting currents (typically 6–8× FLA for a few cycles) to pass without tripping, while still clearing a hard short. For resistive or general-purpose loads, a B or C curve would be a better fit — this one is for inductive, high-inrush circuits.
Mounting and integration
Mounts on DIN rail (EN 60715) or via screw fixing — both methods are supported. The 70 mm installation depth leaves clearance for wiring behind the panel door. Tunnel terminals top and bottom accept copper conductors; the supply cord position is unrestricted, so feed from top or bottom as the layout demands. Sealable design allows the breaker to be locked in the OFF position for lockout/tagout procedures. Supplementary devices (shunt trip, auxiliary contacts) can be added via the product extension feature. The mechanical service life is rated at 10,000 operating cycles — typical for a distribution MCB, not a frequent-switching contactor.