A7B0 Motor Speed Feedback Warning in ABB ACS880 Drive

A7B0 Motor Speed Feedback Warning in ABB ACS880 Drive indicates that the drive is not receiving valid motor speed feedback from the configured encoder or speed feedback device. This warning is generated by the motor feedback monitoring function and typically occurs when the encoder is incorrectly configured, has stopped providing signals, or when there is a mismatch between the motor and encoder settings.

This warning is controlled by:

90.45 – Motor Feedback Fault

Possible Causes:

1. Invalid motor gear ratio settings.
2. Encoder not configured.
3. Encoder configuration changed but not validated.
4. Encoder stopped transmitting feedback signals.
5. Encoder power supply failure.
6. Encoder cable disconnected or damaged.
7. Encoder interface module fault.
8. Mechanical slippage between motor and encoder.
9. Loose encoder coupling.
10. Faulty encoder.
11. Incorrect encoder parameter settings.
12. Encoder communication failure.

Solutions:

1. Read the auxiliary code to identify the specific problem.
2. Verify motor feedback configuration.
3. Check encoder settings in:
   • Group 92 – Encoder 1 Configuration
   • Group 93 – Encoder 2 Configuration
4. Verify encoder interface settings in Group 91.
5. Check encoder wiring and power supply.
6. Inspect the encoder coupling and mounting.
7. Verify that the encoder rotates with the motor shaft.

8. Use:

   • 91.10 – Encoder Parameter Refresh

   after making any encoder configuration changes.

9. Check encoder status diagnostics.
10. Replace faulty encoder or interface hardware if required.

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Auxiliary Code Interpretation

The auxiliary code format is:

XXYYZZZZ

Where:

• XX = Encoder Interface Module Number
  • 01 = Parameters 91.11 / 91.12
  • 02 = Parameters 91.13 / 91.14
• YY = Encoder Number
  • 01 = Encoder 1 (Group 92)
  • 02 = Encoder 2 (Group 93)
• ZZZZ = Specific motor feedback issue.

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Auxiliary Codes and Corrective Actions

Code	Description	Corrective Action
0001	Motor gear definition invalid or outside limits	Check 90.43 Motor Gear Ratio Numerator and 90.44 Motor Gear Ratio Denominator
0002	Encoder not configured	Configure encoder in Group 92 or 93 and execute 91.10 Encoder Parameter Refresh
0003	Encoder stopped working	Check encoder status, wiring, power supply, and encoder signals
0004	Encoder drift detected	Check for mechanical slippage between encoder and motor shaft

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Relevant Parameters

Parameter	Description
90.43	Motor Gear Ratio Numerator
90.44	Motor Gear Ratio Denominator
90.45	Motor Feedback Fault Action
91.10	Encoder Parameter Refresh
Group 92	Encoder 1 Configuration
Group 93	Encoder 2 Configuration

Additional Information

The ACS880 uses motor speed feedback for:

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

When speed feedback is lost or invalid:

• Speed control accuracy decreases.
• Torque control performance may be affected.
• The drive may switch to estimated speed operation.
• Additional encoder warnings or faults may occur.

Recommended Troubleshooting Sequence

1. Record the complete auxiliary code.
2. Identify the affected encoder and interface module.
3. Verify encoder configuration.
4. Check encoder power supply.
5. Inspect encoder cables and connectors.
6. Check encoder coupling and shaft connection.
7. Verify motor gear ratio settings (90.43 and 90.44).
8. Execute 91.10 Encoder Parameter Refresh after configuration changes.
9. Monitor encoder status and actual speed feedback.

Common Symptoms

• No speed feedback indication.
• Unstable speed control.
• Speed reference tracking errors.
• Encoder diagnostics warnings.
• Reduced positioning accuracy.
• Intermittent encoder operation.

Related Warnings and Faults

Code	Description
A7B0	Motor Speed Feedback Warning
A797	Speed Feedback Configuration Warning
A798	Encoder Option Communication Loss Warning
Encoder Faults	Encoder Signal Loss

Proper encoder configuration, secure mechanical mounting, correct gear ratio settings, and reliable encoder communication will help prevent recurring A7B0 Motor Speed Feedback Warnings in ABB ACS880 drives.