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What should I check if my VFD branch fuses are blowing?

Fuses that are blowing ahead of the VFD are not always a sign that there is an issue with the VFD.

Here is a list of things to check in your application that could be causing the fuses to blow:

  1. Are the fuses sized correctly? Consult the VFD manual for fuse sizing requirements. Are the fuses time-delay (slow-blow) fuses?
  2. Is the horsepower/amp rating of the motor too large for the VFD you are using?
  3. Are your voltage readings too high or low for your application? Does the voltage match the ratings for your motors/drives?
  4. For motors with multi-voltage winding configurations: Are the motor-windings connected correctly for the voltage being used?
  5. Is the frequency of the motor(s) in your application 60Hz or some other frequency? Non-60Hz motors require special programming.
  6. Check all contacts on the contactors, fuses, fuse holders, power leads, and all other current-carrying elements ahead of the VFD. Are there any arcing, damaged components, or bad connections?
  7. Thoroughly check for shorts in the brake or motor circuit, including all wiring/leads. A high-potential test may be required.

Address any/all of the above issues if found. If fuses continue to blow in your application due to any of the above sources, this may result in damage to the VFD.