Transformer-protection breaker, 4 A, 100 kA SCCR
Rated voltage goes to 690 V, though at that level the breaking capacity drops to 6 kA, so keep that in mind for 690 V secondaries.
The 4 A continuous rating sets the maximum steady load this breaker will carry without tripping — sized for the primary-side protection of a small control transformer, not a motor branch. No ground fault detection on this variant, so pair it with a separate ground-fault relay if that's required by code.
Accepts 2x (1 … 2.5 mm²) solid or stranded, and 2x (2.5 … 6 mm²) for larger feeds — covers standard panel wire sizes. Zero mm clearance needed at the back or sides, so you can pack breakers tight on the rail. Depth is 96 mm, width 45 mm, height 97 mm — fits standard 45 mm-wide DIN slots.