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Harmonics Issues in Plant
Harmonics Issues caused by large VSD's, air conditioning, etc. in plant.

I have a harmonics issues on an existing plant. In this plant are some large VSD's and air conditioning, etc. What is the best solution to remove these harmonics. The ideal thing would be to add the correction at the Main MV board supplying the MCC's (We have up to 20 separate MCC panels) as we have no room in the existing MCC panels. Is this achievable and would it reduce the harmonics to an acceptable level?


By Bob Peterson on 20 April, 2012 - 8:59 am

There are a few questions that need to be answered first.

1. How do you know you have a "problem"?

2. No matter what you do you will always have some harmonics. What level of harmonics can you live with?

This can be a non-trivial issue and you may wish to get someone who is a competent power engineer involved to do it right. The average salesman selling gizmos to "fix" your harmonic problem is probably a poor choice.

Thanks Bob I think you're right we need to get a Power Engineer involved as Harmonics issues are above my head.

More information is needed

Harmonics can be generated from a wealth of sources and the means to correct them are just as varied. Any thing from VFDs and DC Drives, to an over-sized Transformer supply, or the local utility outside your facility importing Kvar.

I've always been told you need to start with an audit of your Harmonics sources in your facility.

Many VFD manufactures have started adding Harmonics Traps to their larger VFDs and if your VFDs are older the manufacture may have optional equipment that will help out - if the VFDs are indeed the problem.

Thanks Joe,

We are going to get an external power engineer involved.
Unfortunately if there is a harmonics problem we do not have the space at the vsd to install chokes so it will more than likely have to go at the mains distribution board.

By Brian Beal on 23 April, 2012 - 7:51 am

As others have pointed out, determine the source of the harmonics. If it is the VFDs, then add line reactors (sometimes referred to as chokes) to them.

Thanks Brian,

If it does appear to be a VSD problem. The problem with us is we do not have the space at the VSD to install chokes.

That is why I was wondering if there is a solution at the mains feeder to the MCC Panel end

1 out of 1 members thought this post was helpful...

Davy... what do you envision as "correction" to be applied at specific locations?

My reason for the question is to find out if you have been approached by vendors who are promoting installation of "Harmonic Correction Modules", or something similar, to be paid for via an "Energy Savings" proposal.

Regards, Phil Corso

We are being told that the Harmonics level is above the max permissible level. It is planned to get an independent engineer to verify if this is the situation.

Because we are restricted in panel space we need to be able to install some correction to the permissible level and below at the main power distribution board.

This is all dependent on if there is a harmonics situation caused by a VSD issue or if the problem is actually at the transformer feeding the dist board.


By Bob Peterson on 26 April, 2012 - 7:31 am

I am curious on a couple points.

Who told you it was "above the max permissible level"?

Who tested it to determine what the level was?

What criteria was used to determine it was unacceptable?

Unless there is some kind of problem from whatever harmonics you have, why waste any money "fixing" it?

By Bill Schwarz on 24 April, 2012 - 8:37 pm

Yes what you are suggesting is indeed possible. I have implemented a similar solution in my facility by installing harmonic filters at 4160 V bus for harmonics generated by thyristor power supplies at the 480 V level. Consult with a knowledgeable power engineer.

Thanks I will

1 out of 1 members thought this post was helpful...

DAGaj... I don't doubt the veracity of your comments regarding Harmonics! I just wanted to alert you to unscrupulous companies selling modules they claim will eliminate harmonics, correct power factor, and save energy.

Furthermore, THEY WILL EVEN PROVIDE A WRITTEN GUARANTEE that a formidable reduction in electrical energy billing (some even claim 50%) will be realized!

I suggest you read:

Regards, Phil Corso (cepsicon[at]AOL[dot]com)

Thanks Phil,

I do agree with you on the sales people issue.
There should be some come back on the people who promise these miracle engineering cures.

I know sales people will promise you anything to make a sale. The problem is when the equipment is being commissioned the salesman has moved on and you are dealing with a different person.

Finding an honest sales person is sometimes like finding hens teeth.