The A9K23440 is a 4-pole miniature circuit breaker from the Schneider Electric Acti9 iK60N family, rated 40 A at 30 °C with a B-curve (magnetic trip 3–5 × In). The limitation class 3 rating (also per EN/IEC 60898-1) indicates it lets through limited energy during a fault, which helps with downstream equipment protection and selectivity coordination. The B-curve is the key selection parameter here: it trips magnetically between 3 and 5 times the rated current (120–200 A for this 40 A unit). That makes it the correct choice for resistive or general-purpose loads with low inrush — lighting circuits, socket outlets, small distribution feeders — where a C-curve would delay too long on a hard fault. If your BOM line calls for motor or transformer protection with higher inrush, a C- or D-curve sibling would be the better fit.
The 72 mm width (8 × 9 mm pitches) and 85 mm height fit standard distribution board cutouts. Tunnel-type terminals accept up to 35 mm² rigid or 25 mm² flexible cable; strip length 14 mm, tighten to 3.5 N·m.