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How to Keep Up with Developing Motor Drive Issues

by Bassam Dib,, Senior Analyst




On paper winders, the tuning and operation of the motors are at the heart of the process.

Several components of the drive system often begin to fail due multiple causes such as corrosion in flat cables, heat, cold joints, etc. This eventually leads to a complete failure which by that time might have already caused its share of damage. Such events can lead to a disaster if the defective component cannot be quickly identified or if replacement parts are not at hand.

Our continuous monitoring of the motor’s electrical signals triggered an alert on an increase in the error between the expected and the measured rear drum armature voltage.

Our analysis led to the conclusion that there was an abnormal decrease of the rear drum motor flux.

rear drum armature voltage

Our engineers promptly sent the mill a detailed report with supporting graphs and the following recommendations:

  • Check the position of the motor brushes since a change in their position can lead to a drop in the motor field excitation level.
  • Verify the level of the motor field current which could have changed due to a shift in the field current feedback signal fed to the regulator.
  • Replace the drive field control card if found defective.


During the following shutdown, the mill proceeded with these verifications and found that the field control card was defective. They replaced it and we confirmed that the control was restored to its normal operation.

Every mill has strict maintenance programs in place to ensure optimal performance of its equipment at all times. These measures target the components with predictable wear and tear. However, some components can fail unpredictably, like drive control cards for instance. By having the proper tools, it is possible to detect signs of deterioration in these components in order to repair or replace them before they fail and possibly cause further damage.

Our engineers were able to isolate and troubleshoot the issue at an early stage, giving the mill enough lead time to locate a replacement card and replace it during a planned shutdown.

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