A798 Encoder Option Communication Loss Warning in ABB ACS880 Drive

A798 Encoder Option Communication Loss Warning in ABB ACS880 Drive indicates that the encoder feedback signal has been lost or the encoder option module is no longer communicating correctly with the drive. This warning is generated when the drive cannot receive valid feedback from the encoder and the related action parameter (90.45 or 90.55) is configured as Warning.

Encoder feedback is commonly used in closed-loop speed control, torque control, positioning applications, cranes, hoists, and other high-performance motor control applications.

Possible Causes:

  1. Encoder feedback signal lost.
  2. Encoder interface module communication failure.
  3. Encoder cable disconnected or damaged.
  4. Encoder interface module not properly seated.
  5. Damaged slot connector.
  6. Faulty encoder interface module.
  7. Faulty encoder.
  8. Incorrect feedback source configuration.
  9. Fiber optic communication failure (FEA-03 adapter).
  10. Loose fiber optic connection.
  11. Damaged extension adapter.
  12. Electrical noise affecting encoder signals.

Solutions:

  1. Verify that the encoder is selected as the active feedback source.
  2. Check:
    • Parameter 90.41 – Feedback Source 1
    • Parameter 90.51 – Feedback Source 2
  3. Ensure the encoder interface module is fully inserted into its slot.
  4. Inspect the encoder interface module for damage.
  5. Check slot connectors for bent pins, contamination, or damage.
  6. Inspect encoder cables and connectors.
  7. Verify encoder power supply and signal integrity.
  8. If available, test the encoder with diagnostic tools.
  9. Try installing the encoder interface module in a different slot to isolate the fault.
  10. If using an FEA-03 Extension Adapter, inspect all fiber optic connections.
  11. Clean and reconnect fiber optic cables if necessary.
  12. Replace faulty encoder, module, or adapter as required.

Relevant Parameters

ParameterDescription
90.41Feedback Source 1
90.45Action on Feedback 1 Loss
90.51Feedback Source 2
90.55Action on Feedback 2 Loss

Additional Information

The ACS880 can use encoder feedback for:

  • Closed-loop speed control.
  • Torque control.
  • Position control.
  • Hoisting applications.
  • Crane control.
  • High-precision motor operation.

When communication with the encoder is lost:

  • The drive may switch to estimated speed feedback.
  • Control accuracy may decrease.
  • Speed regulation performance may be affected.
  • Additional encoder-related warnings or faults may occur.

Special Check for FEA-03 Extension Adapter

If the encoder module is installed through an FEA-03 Extension Adapter:

  1. Check the fiber optic cables.
  2. Verify fiber optic connectors are fully inserted.
  3. Inspect for damaged fiber optic cables.
  4. Confirm communication LEDs are operating normally.
  5. Replace faulty fiber optic components if required.

Recommended Troubleshooting Sequence

  1. Verify encoder selection in 90.41 or 90.51.
  2. Inspect encoder interface module installation.
  3. Check encoder cables and connectors.
  4. Inspect slot connectors.
  5. Test the module in another slot.
  6. Verify encoder operation.
  7. Check FEA-03 fiber optic connections (if installed).
  8. Monitor encoder feedback values after corrective action.

Common Symptoms

  • Encoder feedback signal loss.
  • Unstable speed control.
  • Reduced torque accuracy.
  • Encoder communication warnings.
  • Drive switching to estimated speed feedback.
  • Intermittent speed feedback issues.

Related Warnings and Faults

CodeDescription
A798Encoder Option Communication Loss Warning
A797Speed Feedback Configuration Warning
Encoder FaultsEncoder Signal Loss
A580PU Communication Warning

Proper encoder wiring, secure module installation, and correct feedback configuration will help prevent recurring A798 Encoder Option Communication Loss Warnings in ABB ACS880 drives.

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