The Schneider Electric A9N3P20DIN is an Acti9 xC60 miniature circuit breaker rated 20 A with a D tripping curve, meaning the magnetic trip operates at 12 x In ±20% — suited for loads with high inrush like motor starters or transformers where a B or C curve would nuisance-trip on startup. It breaks 10 kA at 380–415 V AC and 15 kA at 100–125 V DC, both per IS/IEC 60947-2, so it handles fault currents typical of distribution panels in commercial and light industrial installations. The 3-pole unit clips onto standard 35 mm DIN rail and occupies 6 x 9 mm pitches (54 mm wide).
The D curve's 12 x In magnetic threshold (240 A nominal pickup) is the key selection parameter — it avoids tripping on motor starting current or capacitor bank inrush that a C curve (7–10 x In) would catch. For DC circuits, the 15 kA Icu at 125 V DC covers common battery-bank or UPS distribution.