What the 30 A rating means for fit
The ABB XT4NU2175AFF000XXX is a 3-pole molded case switch from the XT4N 250 TMF family, rated for 30 A continuous on a three-phase system. That 30 A figure is the thermal-magnetic fixed-trip rating — it governs the load it can carry without nuisance tripping and sets the upper bound for the branch circuit it protects. On a 3-phase motor or resistive load, this is the number you match to the nameplate FLA or the calculated load current; oversizing past 30 A means the switch won't clear a fault before the downstream equipment takes damage.