What it is and where it fits
The Siemens 5SL4550-8 is a SENTRON miniature circuit breaker (MCB) with a D tripping characteristic, rated 50 A at 30 °C and 230 V AC. It is a 2-pole unit (1P+N) that occupies 2 modular width units on a DIN rail, making it a direct drop-in for standard residential and infrastructure panels. The D curve means it tolerates high inrush currents — typical for motor, transformer, or lighting ballast loads — without nuisance tripping, while still providing short-circuit protection at 10 kA per EN 60898 and IEC 60947-2.
Ratings that matter for the BOM line
The headline 50 A rating is at 30 °C ambient. At 40 °C it derates to 46.19 A, at 45 °C to 44 A, and at 55 °C to 39.81 A — so if your panel runs warm, size the load accordingly. The 10 kA breaking capacity at 230 V AC covers most residential and light commercial fault levels; the same 10 kA applies under IEC 60947-2 for industrial installations. The D characteristic (10–20× In magnetic trip) is the key selection parameter: it avoids tripping on motor start or capacitor bank inrush where a B or C curve would drop out. The part switches the neutral conductor (1P+N) and includes touch protection on the terminals. It is rated for overvoltage category III and pollution degree 2, which is standard for fixed-installation distribution boards. Mechanical service life is 10 000 switching cycles typical.
Panel integration notes
Mounts in any position on a standard 35 mm DIN rail. Depth is 76 mm (installation depth 70 mm), width 36 mm (2 MW), height 90 mm. Sealable, halogen-free, silicon-free. IP20 with connected conductors — suitable for enclosed distribution boards, not for wet or outdoor locations without a higher-rated enclosure.