Cause : BU earth leakage comes when earth leakage detected by the branching unit: sum of all currents exceeds the level.

An AE06 fault code in your ABB ACS880 drive indicates a branching unit earth leakage fault. The branching unit is an optional module that allows the drive to control multiple motors simultaneously. This fault code signifies that the sum of the currents in all the motors connected to the branching unit exceeds the leakage current limit.

1. Check AC fuses.
2. Check for earth leakages.
3. Check supply cabling.
4. Check power modules.
5. Check there are no power factor correction capacitors or surge absorbers in supply cable.