The Schneider Electric GoPact MCCB 125 G12F3A63 is a fixed-mount, 3-pole molded case circuit breaker with a TM-D thermal-magnetic trip unit, rated 63 A at 40 °C. The LI trip curve gives you thermal overload protection (L) and magnetic short-circuit protection (I) — no ground-fault or short-delay function inside this unit, so keep that in mind when coordinating downstream selective tripping. It is isolation-rated per EN/IEC 60947-2, so it doubles as a visible-break disconnect for lockout-tagout procedures.
Mounts fixed to a backplate, not DIN rail. The 75 mm width, 130 mm height, and 60 mm depth fit standard MCCB cubicle cutouts, but the 25 mm connection pitch and front-facing screw terminals mean busbar stabs and cable lugs land on the same face — no rear-access required. Rated for horizontal or vertical orientation, so it fits both panel layouts and standalone enclosures.
The 63 A trip rating is thermal-magnetic, not electronic — no adjustable long-time or short-time pickup. The magnetic instantaneous trip is fixed, typically around 10x In for TM-D units, so it will hold motor inrush but may coordinate differently with downstream 10 kA MCBs than an electronic trip would. Power dissipation runs 18.7 W per pole at rated current — three poles pull about 56 W total. In a sealed, non-ventilated panel, that heat must be factored into the thermal budget.