The G12F3F50 is a Schneider Electric GoPact MCCB 125 — a fixed-mount, 3-pole thermal-magnetic moulded-case circuit breaker rated 50 A at 40 °C with an F-class breaking capacity of 30 kA at 380/415 V AC. It is built to EN/IEC 60947-2 (and Annex H for selective coordination), carries an insulation voltage of 440 V AC, and is rated for operational voltage of 415 V AC at 50/60 Hz. The TM-D trip unit gives LI protection — thermal for overload (L), magnetic for short-circuit (I). That is the standard combo for distribution feeders: no ground-fault or electronic adjustment, just reliable bimetal and solenoid action.
Thermal environment and mounting reality
Ambient operating range is -20 to 55 °C, storage from -35 to 85 °C. Power dissipation is 18.7 W per pole. Connection pitch is 25 mm, terminals are screw type, and both line and load connections are front-accessed.
Mechanical endurance is 30,000 cycles; electrical endurance is 8,000 cycles at rated current and 415 V. That electrical figure tells you this breaker is meant for infrequent switching — it is a distribution protector, not a motor-starting contactor. If your application cycles the breaker weekly, 8,000 cycles is decades of service. If it cycles daily, you will wear out the contacts sooner and should consider a contactor in series. Utilisation category A means it is not specifically rated for high-frequency switching of motors or capacitive loads — standard distribution duty. Altitude rating: full performance up to 2000 m, derated above that up to 5000 m. If your site is above 2000 m, factor in the reduced dielectric strength and cooling.