The ABB S283UC-Z25 is a 3-pole miniature circuit breaker from the S280UC series, rated 25 A with a Z-curve trip characteristic for 500 VDC applications.
The Z-curve trips between 2.5× and 4× In (62.5 A to 100 A magnetic release), which is tighter than a B-curve and faster than a C-curve. That matters when you're protecting semiconductor loads or long DC cable runs where inrush is low but short-circuit clearance needs to be quick — it avoids nuisance trips on moderate overloads while still clearing a hard fault before the downstream devices cook. Rated 500 VDC across three poles in series means this breaker handles the voltage stress of a 500 V battery bank or a DC bus in an industrial drive system. The 3-pole construction ties all three poles mechanically and electrically so that a fault on any one pole opens all three — no single-pole dropout leaving partial voltage on the load side.