What the 125 A Frame Rating Means
The XT2SU3040AFF000XXX: The 125 A frame rating on the XT2S series means the breaker's physical housing and internal contacts are sized for continuous currents up to that level. The TMF trip unit provides fixed thermal-magnetic protection, so the breaker is a non-interchangeable, factory-set device — no field-swappable trip unit. This suits applications where the protection curve is known at design time and won't need adjustment later.
Where the XT2S Series Fits
The XT2S series mounts in standard panel or enclosure footprints, typically on a DIN rail or direct-mount plate. It is used for branch-circuit protection in distribution panels, motor control centers, and industrial machinery where a compact, fixed-trip MCCB is specified.