VFD Harmonic Filters

All,

I have searched the forum and cannot find anything to help answer my question. Regarding VFDs, what criteria is used to determine the type of filters needed for a VFD installation.

IEEE 519 has a ITHD of 5% at the PCC, but at a component level, when do you determine to use a line reactor, a line reactor and harmonic filter, a sinusoidal filter, etc. Are there applications where you would only need one type of filter vs. multiple and how is that determined?

Best Regards

There is a lot of gray area and some significant snake oil regarding harmonics and VFDs. The best way is to ask the drive supplier to run a harmonic analysis of your system. Most will do this without charge.

If you need IEEE-519 compliance there are many ways to do this. They include active front ends, reactors, and 18-pulse or similar drive architectures. I usually leave it up to the supplier. If tehy are willing to gaurantee compliance with a specific technology then you should be in good shape.

Tom is correct about suppliers running a harmonic analysis for you but, be prepared to provide transformer impedance, length of leads of all branches in the network, a list of all loads and their harmonic contribution to the network, and the drive harmonic characteristics.

With that, the harmonic content of the proposed system can be accurately predicted.

The problem, as I supposed has already become apparent to you is, how do I get all this data? A nasty problem indeed!