The MGP36400YP is a PowerPact M unit mount breaker from Schneider Electric's MJ frame family — a 400 A, 3-pole electronic trip unit rated 18 kA at 600 VAC. The 'unit mount' form factor means it bolts directly into switchboard or panelboard bus, not onto a DIN rail. It ships with lugs off the end (line and load connections at opposite ends) and includes a handle padlock provision for lockout/tagout compliance. This is a fast-moving critical spare for plants with PowerPact M distribution sections — when one fails on a 400 A feeder, the line stops until the breaker is swapped.
What the 18 kA interrupting rating means
For a 400 A feeder, that covers most industrial secondary-side faults.