# Thread: Harmonic Currents In Single Phase

1. Member
Join Date
Aug 2003
Posts
36

## Harmonic Currents In Single Phase

Why is it that harmonic currents are not such a big problem with Single phase and they are on three phase? What happens if you have someone with 5 computers and non-linear loads in a residence will this be a problem?

2. Senior Member
Join Date
Feb 2003
Posts
638

## Re: Harmonic Currents In Single Phase

In single phase the neutral will not be carrying any more current than the hot.

In three phase with one neutral, the harmonics build up on the neutral due to the fact that 180Hz, etc does not cancel between the phases, so the neutral can be carrying more current than any of the phases. One remedy is using 3 neutrals, so that it is like 3 single-phase circuits. The other remedy is a larger neutral.

To prevent harmonics check with Dereck!

Karl

3. ## Re: Harmonic Currents In Single Phase

Originally posted by hde_electric:
Why is it that harmonic currents are not such a big problem with Single phase and they are on three phase? What happens if you have someone with 5 computers and non-linear loads in a residence will this be a problem?
Nothing happens with 5 computers in a residence with single phase service.

4. ## Re: Harmonic Currents In Single Phase

Durn I love the internet:

(and all of you harmonic causing end users)

HDE check this out

http://www.copper.org/pq/issues.html

5. Senior Member
Join Date
Feb 2003
Posts
638

## Re: Harmonic Currents In Single Phase

Thanks Brian, great source. Tells it all.

Karl

6. ## Re: Harmonic Currents In Single Phase

Originally posted by karl riley:
Thanks Brian, great source. Tells it all.

Karl
I read the white paper and found it informative. However I found thier reccomended solutions a little biased, which they alluded too. All the solutions were copper based, which is what you would expect from the copper industry. What they did not mention was the most effective means such as MG and dual conversion UPS. Just some food for thought.

7. ## Re: Harmonic Currents In Single Phase

dereck,
They also never talk about the use of true single phase distribution to prevent excessive current on the neutral with nonlinear loads.
don

8. ## Re: Harmonic Currents In Single Phase

hde A good book for your library.

http://web.idirect.com/~a1parts/mw_handbook.html

9. ## Re: Harmonic Currents In Single Phase

Just wanted to add a little to the previously made informative posts.

Yes, there will still be Harmonic Currents involved with a 1Ø System, but the effects on the Common Grounded (Neutral) Conductor of Multiwire Circuits aren't like those of Polyphase Multiwire Circuits (3Ø 4 Wire Wye Systems).

The level of Distortion needs to be considered. 10% THD would include an additional 10% Line Current on the 2 Wire Circuit. 20% THD adds 20% more, and 33% adds 33% more.

On 3Ø 4 Wire Wye Systems using 4 Wire Multiwire Branch Circuits for Loads having » 30% THD, the Common Grounded Conductor will be carrying upto (or possibly more than) 200% of the Load Current.

I have given some very basic, simple descriptions here, but they cover the topic enough to give you more ideas of what to look for in studies.

Scott

p.s. - it's been Eons since my last post in this forum! How are all of you?

Scott35

10. ## Re: Harmonic Currents In Single Phase

Hello Scott, nice to hear from you again. How's the locomotive world treating you?

Roger

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