DC Bus Undervoltage

What does LU mean?

The DC bus voltage has dropped below acceptable limits, typically due to low incoming mains voltage or an issue with the power supply module. Incorrect controller wiring to the mains (e.g., 400V controller on 240V mains) can also trigger this. Persistent undervoltage can cause intermittent operation or prevent the drive from starting.

Additional Steps

Steps 1–2 are listed in Priority Fix.

1. 3

   Confirm the controller is connected to the correct mains voltage configuration (e.g., 400V unit to 400V mains supply).