A better understanding

[joeyww12000]

I posted a question about harmonics and there role in comprimising a circuits integrity due to the use of electronic ballasts in a MWBC. My foreman is a very stubborn man when it comes to his electrical theory knowledge, his being wrong I mean.....Such as saying a 277v circuit doesnt have voltage drop...! Whatever... Anyway my question is could someone explain in the most simplistic of terms what harmonics are and how they are created by electronic ballasts. Do they create enough problem that you would always pull seperate neutrals for all your lighting that has electronic ballasts? Or is this just another one of my foremans attempt to be right all the time? He wants to be right for his ego, I just want correct information to gain true electrical knowledge. Thank you.

 

[dicklaxt]

Take a look at this link

http://smtc.uwyo.edu/ess/Planbook/harmplan.html

 

[Lcdrwalker]

An electronic ballast typically operates at 180 Hz. That is the third harmonic addressed in site above (good site). At the peak (or trough) of the 60Hz wave, a corrosponding peak of the 180Hz can occur. These peaks would then be addative. If the MWBC were loaded to its maximum ampacity, the added peak could cause an over current condition on the common neutral. If a dedicated neutral is installed, that neutral would only carry the current of that circuit.

 

[iwire]

If a dedicated neutral is installed, that neutral would only carry the current of that circuit.

Lets not forget it will still be additive on the feeder and transformer.

I would not want anyone to go away from this thinking two wire circuits eliminate harmonic currents. :smile:

 

[76nemo]

I am glad you threw that in. There is alot of arguement here on the issue.

 

[iwire]

There is alot of argument here on the issue.

I still not sure what you mean. :-?

Harmonic currents definitely exist, but outside of theory even without 'super neutrals' they are rarely damaging to modern electrical system.

 

[76nemo]

I still not sure what you mean. :-?

Harmonic currents definitely exist, but outside of theory even without 'super neutrals' they are rarely damaging to modern electrical system.

You see, Bob can be nice, I think he would rather tell me to sh*tup:grin: Kidding. We already have had this discussion on MWBC's and neutrals. There is a present problem, although not encountered everyday, the problem exists. We have dedicated neutral pulls for a reason.

 

[roger]

We have dedicated neutral pulls for a reason.

There is no such animal.

But, the bottom line is, branch circuit conductors are not that much of a problem whereas accumulative harmonics on transformers can be.

This can be helped a number of ways.

The truth is, the manufacturers of the equipment that cause the problem should fix it.

Roger

 

[76nemo]

There is no such animal.

But, the bottom line is, branch circuit conductors are not that much of a problem whereas accumulative harmonics on transformers can be.

This can be helped a number of ways.

The truth is, the manufacturers of the equipment that cause the problem should fix it.

Roger

Roger, again, let me back up. Many of you work the construction field, I applaud you. The manufacturers of todays equipment is one thing. What about the manufacturers from the 70's/80's???? We can't deny harmonic distortion as a problem. Would you argue your point 10 years ago on switch modes?