What the 125 A rating means for your panel
The ABB XT1NU3080AFF000XXX is a Tmax XT1N frame breaker rated 125 A continuous, 3-pole, with a thermal-magnetic fixed trip set at 80–800 A (factory-set within that band). The thermal-magnetic trip responds to both overload (thermal bimetal, inverse-time curve) and short-circuit (magnetic instantaneous), so it covers motor starting and fault clearing in one device.
Frame-mounted design with front flat terminals — bolts directly into a switchboard or panel bus, not a DIN rail. The flat terminal face accepts standard lug or bus-bar connections; torque values per the ABB mounting instructions. Three-pole configuration suits three-phase feeders, branch circuits, or motor protection in a distribution panel.