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ErrorLib — Industrial Fault Code Library

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UL5

Mechanical Weakening Detection 2

Yaskawa · J1000

What does UL5 mean?

The operating conditions detected by the drive matched the criteria for mechanical loss detection set in parameter L6-08. This suggests an undertorque condition due to potential mechanical weakening or a problem on the load side that needs investigation to prevent further damage.

Common Causes

  • Mechanical loss detection criteria (L6-08) set too sensitive for normal variations in mechanical system performance.
  • Gradual wear of bearings, gears, or other mechanical components leading to reduced load or efficiency.
  • Partial blockage or flow reduction in pump/fan applications causing lower motor current.
  • Drive not properly tuned to the mechanical system, causing misinterpretation of normal operating current.
  • Degradation of the motor itself, such as inter-turn shorts, leading to reduced torque output for a given current.

Repair Steps & Checklist

Click steps to track your progress.

  1. 1

    1. Review and potentially adjust the mechanical loss detection parameter (L6-08) to match the actual expected mechanical system performance.

  2. 2

    2. Perform a full mechanical inspection of the driven equipment for signs of wear, misalignment, or reduced efficiency.

  3. 3

    3. Monitor motor current (U1-01) over an extended period to identify any gradual changes or trends indicative of mechanical weakening.

  4. 4

    4. Consider running an auto-tuning procedure (A1-02) to re-optimize motor parameters if mechanical characteristics have changed.

  5. 5

    5. Check for consistency in fluid levels, filter status, or material flow in process applications where load can fluctuate.

  6. 6

    6. If the fault persists and no external mechanical issues are found, investigate potential degradation of the motor itself.

Browse all codes in this manual (59)
Verified technical data. Last updated: April 2026

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Source: Yaskawa J1000
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