Rated current and breaking capacity
The A9F05420 is a 20 A rated miniature circuit breaker from the Acti9 iC60N range, 4 poles, D curve. The D curve magnetic trip triggers at 12 x In ±20 % — meaning it holds through motor inrush and transformer energization without nuisance tripping, then clears fast on a hard fault. Breaking capacity hits 36 kA Icu at 12-133 V AC (EN/IEC 60947-2), 20 kA at 220-240 V, and 10 kA at 380-415 V. That covers most industrial distribution panels fed from a 400 V transformer secondary. The part carries dual certification to EN/IEC 60947-2 (industrial) and EN/IEC 60898-1 (domestic), so it qualifies for both plant-floor and building-power applications.
Snaps onto DIN rail — standard 35 mm profile. Width is 72 mm (8 x 9 mm pitches), so it occupies four module spaces in the enclosure. Depth 78.5 mm, height 91 mm. Terminals accept 1-25 mm² rigid or 1-16 mm² flexible wire; tightening torque 2 N.m. Strip length 14 mm. IP20 finger-safe terminals. The thermal-magnetic trip unit is non-interchangeable — no field-swap of the trip element. Earth-leakage protection requires a separate Vigi iC60 block, not built in.