AL028 alarm in delta ASDA-A2 servo drive indicates Encoder voltage error or the internal of the encoder is in error. This means battery voltage is too high.

1. Check if the charging circuit exists in the servo drive.
2. Check if it is the absolute type encoder.
3. Check if the servo is properly grounded.
4. Check if the encoder cable separates from the power supply or the high-current circuit to avoid the interference.