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Dealing with Harmonics in AC Drives

October 24, 2019

A phenomenon known as harmonic distortion can occur for the voltage and current produced in an electrical system, such as an AC drive (also known as a variable frequency drive (VFD)), as a result of non-linear loading.


This harmonic distortion, in the case of a VFD, originates from the power switching devices that produce fluctuating supply frequencies.


While harmonics are a natural occurrence in such equipment, particular harmonic frequencies have been known to resonate with capacitors. This resonation propagates the generation of large currents and voltages, leading to equipment damage.


How Are Harmonic Issues Dealt with in an AC Drive?

First off, it is important to look out for the symptoms of harmonic issues within your AC drive before deciding on a course of action. Some of these effects include:


  • Fuse and capacitor failure
  • Higher run temperatures than normal
  • Increased energy consumption
  • Accelerated wear on insulation
  • Inconsistent torque cadence


Once you’ve noticed one or more of these symptoms afflicting your drive, you can utilize the expertise of a repair service, such as those provided at Bauer GMC, upon which a technician can use an oscilloscope and power harmonic analysers to measure the severity and distortion of the harmonics.


Resolving such an issue can involve some of the following solutions:


Independent Power

In an optimal environment, dedicated transformers and feeders would be established to provide the power needed within a drive, effectively cordoning off any interferences.


Reduced Cabling

The length of cabling should be as minimal as possible in order to mitigate harmonic distortions. A good rule of thumb is to aim for cabling that is no longer than 15m.



Custom harmonic filters can be manufactured to truncate specific amplitudes from a number of fixed frequency currents, curtailing their efforts to enter the system.


The Bauer GMC Difference…

We understand the importance these drives play within industry, which is why we make a concerted effort to always provide you, the customer, with the highest quality drives on the market through our scrutiny in production and testing. We don’t let factors like harmonic distortion get in your way, by tailoring our drives to the unique situations of our clients you can be sure your Bauer drive will serve you well!