What it is and where it fits
The ABB S281UX-K16 is a 1-pole miniature circuit breaker (MCB) with K-characteristic, designed for snap-on mounting to a standard DIN rail in a distribution board or control panel. The K-curve trips between 8 and 12 times rated current, making it suited for loads with moderate inrush — motor circuits, transformers, or lighting banks where a B- or C-curve would nuisance-trip on startup.
