The MGN60903 is a C60N miniature circuit breaker from Schneider Electric's Multi9 range — a 4-pole, 3 A thermal-magnetic unit with a C curve and 20 kA breaking capacity at 240 V AC. It's built to EN/IEC 60947-2, Category A, and rated for isolation duty. The 35 mm DIN-rail mount and tunnel terminals (up to 25 mm²) make it a straight swap into existing distribution boards or sub-panels.
The 3 A rating at 50 °C (per EN/IEC 60947-2) sets the continuous current limit before the thermal element starts its trip curve — sized for a 3 A resistive or lightly inductive load, not a motor starting surge. The C curve means magnetic trip occurs at 8.5× In (±20 %), so it holds through moderate inrush (small transformers, capacitor banks) but clears fast on a hard short. Breaking capacity is the headline: 20 kA Icu at 240 V AC phase-to-phase (10 kA at 415 V, 6 kA at 440 V). The Ics (service breaking capacity) is 75 % of Icu at each voltage level, so after one high-fault interruption the breaker still clears subsequent faults at that reduced rating. The 4 protected poles cover three-phase plus neutral, common for distribution sub-feeds in commercial or light industrial panels.
Occupies 8 modules of 9 mm pitch (72 mm total width) — count that against your enclosure fill factor before ordering.
Certified to EN/IEC 60947-2, with pollution degree 3 (conducive to industrial environments with occasional condensation or conductive dust). The suitability-for-isolation marking (per the same standard) means it can be used as a disconnecting means for safe maintenance — the contact position indicator gives visual confirmation of open/closed state. Earth-leakage protection requires a separate block (not integrated).