VFD line filter

[polvalrot]

Dear All
quite often we see installations of VFDs without the line harmonics filters (i do not mean the line chokes), concequently meading to failures to nearby capacitor banks installations.
What would be the recommended retrofit as regarding the input "cleaning"?

 

[aolalde]

In my opinion first measure the harmonic frequencies that are generated and then design (or buy) the filters according to the measured frequencies result.
A generic recommendation when using VFD’s is to avoid power factor correction capacitive banks in the same power line.

 

[Skogsgurra]

Yes. And to add to aolalde's good advice; there are harmonics and there are high-frequency components in the line volage. Both harm your capactors. HF components are not as energetic as the harmonics and do harm to low-valued capacitors like lamp capacitors and similar.

Using power factor correction capacitor on same transformer as you have SCR and VFD drives is not recommended - at least not if the drive load is approaching about 20 percent of transformer capacity.

Gunnar Englund

http://www.gke.org

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100 % recycled posting: Electrons, ideas, finger-tips have been used over and over again...

 

[thinker]

You also might be able to use IEEE 519-92 recommended formula (square root of the ratio of short circuit power to kVAR rating of capacitors battery)to evaluate a frequency of a possible resonance. The impact depends upon type of the converter and spectrum of its voltage and current harmonics. You might need a combination of the tuned and low-pass filters.And yes, harmonic study is a must.