61

Feedback error

Danfoss · VLT HVAC Drive High Power

What does 61 mean?

An inconsistency has occurred between the calculated motor speed and the speed measurement received from the feedback device (e.g., encoder). This indicates a potential issue with the feedback device, its wiring, or the drive's speed calculation, which can lead to unstable speed control or unexpected motor behavior.

Common Causes

  • Damage to the encoder feedback cable or poor connection at the drive's feedback terminals.
  • Faulty encoder device itself (e.g., internal damage, dirty optics, bearing wear).
  • Incorrect encoder PPR (Pulses Per Revolution) setting (P7-10) in the drive's parameters.
  • Mechanical slippage or misalignment between the encoder shaft and the motor shaft.
  • Excessive electrical noise or interference on the encoder signal lines.
  • Motor operating in a highly dynamic or unstable manner that exceeds encoder tracking ability.

Repair Steps & Checklist

Click steps to track your progress.

  1. 1

    1. Verify physical connection of the encoder cable to the drive's feedback terminals (e.g., terminals 32-35).

  2. 2

    2. Inspect the encoder cable for insulation damage, cuts, or crimping along its entire length.

  3. 3

    3. Confirm Parameter P7-10 (Encoder Pulses/Rev) precisely matches the actual PPR rating of the installed encoder.

  4. 4

    4. Check for voltage output from the drive's encoder power supply terminals (e.g., terminal 50) using a voltmeter.

  5. 5

    5. Use an oscilloscope to check the encoder A/B/Z phase signals at the drive's feedback input terminals for clean waveforms.

  6. 6

    6. Check for mechanical play or looseness in the encoder coupling or mounting to the motor shaft.

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Verified technical data. Last updated: March 2026

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Source: Danfoss VLT HVAC Drive High Power