Cause : Undervoltage comes when DC link voltage undervoltage comes when the power unit has detected an undervoltage condition in the DC link.

"Err09" fault indicates that the voltage level in the DC link has dropped below the acceptable threshold.

1. The rectifier bridge, the buffer resistor, the drive board or the control board are abnormal.
2. Check drive rectifier section using multimeter.
3. The AC drive's input voltage is not within the permissible range.