The A9F05450 is a 4-pole Acti9 iC60N miniature circuit breaker rated 50 A with a D tripping curve. The D curve means magnetic trip occurs at 12× In (600 A) ±20 %, so it handles the high inrush of motor and transformer loads without nuisance tripping — a standard choice for distribution subfeeds feeding inductive equipment. Thermal-magnetic trip technology combines a bimetal for overload protection and a solenoid for short-circuit response, so the breaker covers both sustained overcurrent and fault conditions in one unit. Breaking capacity is rated at 36 kA Icu at 12–133 V AC, 20 kA at 220–240 V, 10 kA at 380–415 V, and 6 kA at 440 V per EN/IEC 60947-2, plus 10 kA Icn at 400 V per EN/IEC 60898-1.
The 72 mm width (8 × 9 mm pitches) matches the 4-pole footprint; 78.5 mm depth and 91 mm height leave room for wiring in a standard distribution enclosure. Double terminals top and bottom accept 1–35 mm² rigid or 1–25 mm² flexible cable, with a 14 mm strip length and 3.5 Nm tightening torque. The IP20 finger-safe terminals are fine for enclosed panels; no washdown rating here. A trip indicator on the toggle gives local visual status — useful for a panel walk-down. Earth-leakage protection requires a separate Vigi block; the breaker itself is thermal-magnetic only, so if RCD protection is needed, plan for the add-on module downstream.