Trip unit identity and fit
The LE3400U43X is a Micrologic electronic trip unit for Schneider Electric PowerPacT L molded-case circuit breakers. It carries the LSI protection curve — long-time, short-time, and instantaneous — plus an integral ammeter for local current readout. The adjustable rating range spans 125A to 400A, with a fixed 5.3A sensor rating that sets the base scaling.
The 5.3A sensor rating is the current transformer tap — it defines the minimum pickup floor for the protection algorithms. The 125A to 400A adjustable range means the same trip unit covers a wide spread of frame sizes; you set the actual continuous-current rating via the dial on the front face. LSI protection gives you separate time-current adjustment for overload (long-time), short-delay (short-time), and instantaneous fault trip — useful for selective coordination in a distribution panel where you need the downstream breaker to clear first.
Deployment context
Mounts into the PowerPacT L breaker frame as a plug-in module. The breaker itself bolts into a panelboard or switchboard enclosure — typical install for commercial and light industrial distribution, 480VAC or 600VAC feeder circuits. The ammeter display is front-facing for at-a-glance load monitoring without opening the door.