What the K-curve means for your circuit
The S202-K4 is a 2-pole supplemental protector from ABB's S200 series, rated 4 A at 277 V AC with a 6 kA interrupting capacity. The K-curve trips between 8 and 12 times rated current — faster than a D-curve on moderate overloads but slower than a B or C curve, which makes it a common choice for motor branch circuits, transformer primaries, and inductive loads where you need to ride through inrush without nuisance tripping. It's listed under UL 1077 as a supplemental protector, not a branch-circuit rated device, so it's intended for internal panel protection downstream of a listed branch breaker.
DIN-rail fit and panel integration
Mounts on standard 35 mm DIN rail. Two-pole form factor means it occupies two module widths — 36 mm total — which is the same footprint as the S202M-C10 and other S200 2-pole siblings, so swapping between them requires no rail repositioning or busbar rework. The screw terminals accept up to 25 mm² conductor, and the busbar comb slots are compatible with ABB's PS series pin and fork busbars.