It is important to have a healthy and well-functioning Variable Frequency Drive (VFD) for your electric motor to run properly. Without this, your machine will not be able to process the load effectively. 

Here are some of the key reasons for the failure of a VFD and effective ways for VFD troubleshooting:

  • Overcurrent Fault

Overcurrent is often caused by circuit overload or short-circuit, an arc fault or a ground fault. You may require a VFD drive repair done if your drive is facing these issues. 

For overcurrent issues, it is advisable to check all power connections, ensuring that the connections are strong. Loose connections often result in such faults. 

The auto-tuning feature of a VFD often comes handy in troubleshooting VFD problems. This feature allows your drive to identify the motor attached to it. This further allows the rotor information to be used for better control of the current.

  • High Bus Fault

High Bus fault can be caused due to a sudden increase of voltage in the AC line. Excessive load generated by the inertia of your machine can also result in this issue.

Here, your VFD would trip and shut down the insulated gate bipolar transistors (IGBTs). This way, it would protect itself.

If there such a fault is indicated, always make sure that your motor is receiving a consistent AC power supply. Also, always ensure that the deceleration time matches the capacity of the load.

  • High Starting Current/Load

If your motor is experiencing high starting current/load, there might be an issue of mechanical binding or other relevant changes in the speed of load of your machine. VFD overload can occur even if loads are run at a few more RPMs.

The most common way of VFD troubleshooting here is to use a VFD having an extended acceleration rate. This would facilitate a slow and smooth start of the load/current instead of the motor experiencing a jerk. 

  • Inconsistent Operation Of The Drive

There may be situations when you cannot pinpoint the fault but your VFD is operating erratically. Do not make the mistake of overlooking this issue and try to understand a root cause of the problem. If you are not able to see what it wrong, it is advisable to go for a VFD drive repair.

However, you can always start by monitoring your VFD for overheated or burned components. If you find signs of cracking or discolouration in the drive, get the faulty portions repaired and test the drive before putting it back in action.

  • Failure Due To Contamination

Your VFD might get contaminated with dust, moisture or other airborne particles. Issues like this can be identified by arcing marks across circuit board traces or other key components. 

If the drive faces extreme contamination, it is advisable to take the drive away from the source of contamination immediately and provide it a NEMA-rated enclosure. 

  • Failure Due To Temperature

The temperature around your VFD while it is functioning might cause its failure. Always make sure that your drive functions within advisable temperature limits. 

Make sure you measure the temperature inside and outside the drive enclosure and confirm that it is in sync with the temperature deemed ideal by the manufacturer.

  • Failure Due To Buildup

“Buildup” is a term commonly used for dust along with plant air infused with metallic particles, oil and moisture. This is an issue of severe contamination and requires instant VFD troubleshooting. 

The only way to prevent this issue is cleaning your drive on a regular basis and using a VFD that is suitable for your plan environment.

  • Excessive Heat

This is an extension of VFD failure caused by temperature. Excessive heating is commonly caused due to “buildup”, current exceeding the rated level or connections that are loose.

In such situations, it is advisable to use a temperature probe and maintaining a clean environment for your drive at all times. Also, go for VFD drive repair immediately if you find a leaking capacitor. 

  • Presence Of Moisture

Excessive moisture in plants often results in corrosion, causing damage to the circuit boards. Lower running of VFDs may result in unwanted condensation inside your machine.

It is advisable to use dehumidifiers for dealing with this issue. If possible, make sure you use VFDs with sealed housing and put the stored backup VFDs into use to prevent issues arising due to unwanted moisture. 

  •  Other Relevant Issues

There are many other issues that may cause your VFD to fail, some of which include:

  • Load or speed variation
  • Power issues
  • Changes in plant environment
  • Mishandling 

Many of these issues cannot be immediately recognised. You need to be vigilant and alert, making regular VFD checkups to ensure that your drive is functioning in a healthy and sustainable manner.

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