The XT4NU3150BJJ000XXX is an ABB XT4N molded-case circuit breaker with a 250 TMA (thermal-magnetic adjustable) trip unit. It sits in the XT4 frame, which is the compact, high-density line in ABB's System pro M power distribution range — sized for panelboard and switchboard integration where space is tight but fault-current ratings need to hold.
What the 250 TMA rating means for fit
The 250 TMA designation tells you the thermal pickup and magnetic trip thresholds are field-adjustable within the frame's continuous current rating. That matters when coordinating with downstream branch breakers or upstream feeders — you dial in the long-time and short-time bands to match the load profile without swapping the entire breaker. Mounts in the standard DIN-rail footprint common to the XT4 family. Panel cutout and bus-bar spacing match the ABB XT4 line; no adapter plate needed for most switchboard layouts.