The Schneider Electric MGN25127 is a C60H miniature circuit breaker from the Multi9 range, rated 4 A at 50 °C with a D tripping curve. The D curve's magnetic trip threshold of 12 x In (+/- 20 %) means it tolerates the inrush of motor starters and small transformers without nuisance tripping — a common pain point when a C-curve breaker is spec'd on a lightly inductive load. Three poles protected, thermal-magnetic trip unit, rated operational voltage up to 440 V AC.
The 30 kA Icu at 240 V AC is the headline number, but the service breaking capacity Ics tells the real story for coordination: 15 kA at 240 V (50 % of Icu). That means after clearing a fault at 15 kA the breaker remains functional — you do not automatically replace it after a downstream short. At 415 V the Ics drops to 7.5 kA, at 440 V to 5 kA. For a 3-pole breaker on a 400/415 V distribution board, the 7.5 kA Ics is the figure to coordinate with the upstream device.
Snaps onto 35 mm symmetrical DIN rail (EN 60715). The 54 mm width (6 x 9 mm pitches) occupies three modular spaces — standard for a 3P MCB in any European-style panel.