The ABB S201MUC-K2 is a single-pole miniature circuit breaker from the S200MUC series, rated 2 A with a K-curve trip characteristic.
The K-curve (trip between 8× and 12× In) is designed for inductive and motor-starting loads — it holds through the inrush without nuisance tripping, unlike a B-curve that would trip on the same surge. At 2 A, this breaker is sized for small control transformers, solenoid valves, or contactor coils drawing under 2 A continuous. The 6 kA interrupting rating at 277 VAC means it can safely clear a fault up to 6,000 A on a 277/480 V wye panel. The DC side is rated 10 kA at 250 VDC, which covers most industrial control-circuit DC supplies.
Single-pole width means it takes one module space (roughly 17.5 mm) on the rail — useful when packing multiple circuits into a small enclosure.