AL026 alarm in delta ASDA-A2 servo drive indicates Unreliable internal data of the encoder. This means the encoder is in error. Errors occur in the internal data for three consecutive times.

1. Check if the servo is properly grounded.
2. Check if the encoder cable separates from the power supply or the high-current circuit to avoid the interference.
3. Check if the shielding cables are used in the wiring of the encoder.