The ABB S203-K5 is a 3-pole miniature circuit breaker from the S200 series, rated 5 A with a K-curve trip characteristic. It carries a 480Y/277 VAC rating and a 6 kA interrupting capacity, classified as a UL 1077 supplemental protector. The K-curve means it tolerates moderate inrush — typical for motor control or transformer primary protection — without nuisance tripping, while still clearing faults within the 6 kA limit.
What the Ratings Mean for Fit
The 5 A rating is the continuous current the breaker carries without tripping; the K-curve's magnetic trip threshold (typically 10–14× In) lets it pass the starting surge of a small motor or transformer that would trip a Z-curve. The 6 kA interrupting capacity at 480Y/277 VAC means it safely clears a fault up to that level — adequate for most branch circuits in a 480 V panel, but verify available fault current at the point of installation. The DIN-rail footprint clips directly into a standard 35 mm rail, so it swaps into an existing S200-series panel without rework.
Compliance and Documentation
Listed under UL 1077 and CSA 22.2 as a supplemental protector — not a branch-circuit rated breaker (UL 489), so it's intended for internal equipment protection rather than service entrance or feeder duty. The S200 series carries CE marking and RoHS compliance per ABB's standard declaration. For a BOM freeze or quality doc-control pass, the UL/CSA listing and manufacturer's declaration of conformity are available on request.