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:
- Are the fuses sized correctly? Consult the VFD manual for fuse sizing requirements. Are the fuses time-delay (slow-blow) fuses?
- Is the horsepower/amp rating of the motor too large for the VFD you are using?
- Are your voltage readings too high or low for your application? Does the voltage match the ratings for your motors/drives?
- For motors with multi-voltage winding configurations: Are the motor-windings connected correctly for the voltage being used?
- Is the frequency of the motor(s) in your application 60Hz or some other frequency? Non-60Hz motors require special programming.
- 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?
- 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.