The ABB S803U-K25 is a 3-pole miniature circuit breaker from the S800 series, rated 25 A at 240 V AC with a K trip curve and a 50 kA interrupting capacity. It snaps onto a DIN rail for panel integration — standard for distribution boards and sub-panels where you need branch-circuit protection with a high fault-current rating.
The 25 A continuous rating and K trip curve mean this breaker is designed for motor and transformer loads — the K curve holds longer through inrush than a B or C curve, so it won't nuisance-trip on a motor start but still clears a hard fault fast.