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Old 01-29-2015, 07:25 AM   #21
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There are no harmonics in a 120/240V system, which is why they are used for applications where harmonic producing equipment is used.

Oversizing neutrals is a waste of money.
There are harmonics, they are NOT ADDITIVE ion the neutral.

Harmonics are a result of the way a load draws current, excessive current harmonics will affect the voltage. Excessive phase current harmonics in a Wye system are additive in the neutral.

I can post some Scope snapshots later, heading to the ski slopes now a more important endeavor.
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Old 01-29-2015, 07:27 AM   #22
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I can see the oversize neutral to a panel, but at the MDP to the xfmr,? How far do you go.
To the source if excessive current is the issue.
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Old 01-29-2015, 07:52 PM   #23
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Quote:
Originally Posted by Bad Electrician View Post
There are harmonics, they are NOT ADDITIVE ion the neutral.

Harmonics are a result of the way a load draws current, excessive current harmonics will affect the voltage. Excessive phase current harmonics in a Wye system are additive in the neutral.

I can post some Scope snapshots later, heading to the ski slopes now a more important endeavor.
I will rephrase.

Harmonic current does not flow on nuetrals in single phase 240/120V systems. All the harmonics cancel themselves out. They can not circulate in the transformer windings.

Running "super nuetrals" because of harmonic currents, is a waste of wire.

Please show me a screen shot of a single phase system nuetral with excess current flowing on it, because of harmonic currents.

If you want to trade screen shots of harmonics on 3 phase 208V systems, I'll try to check in more often as I have plenty taken with my fluke 434.
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Old 01-29-2015, 07:59 PM   #24
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Never mind swapping screen shots Brian, I forgot the laptop I had used died years ago.
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Old 01-29-2015, 07:59 PM   #25
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Quote:
Originally Posted by Helmut View Post
I will rephrase.

Harmonic current does not flow on nuetrals in single phase 240/120V systems. All the harmonics cancel themselves out. They can not circulate in the transformer windings.

Running "super nuetrals" because of harmonic currents, is a waste of wire.

Please show me a screen shot of a single phase system nuetral with excess current flowing on it, because of harmonic currents.

If you want to trade screen shots of harmonics on 3 phase 208V systems, I'll try to check in more often as I have plenty taken with my fluke 434.
Dude, you're dealing with the very top electrician in northern va. You're just making yourself look silly. Fluke 434? That's a toy. He'll throw that in the trash can of the white house next time he's in there. Just do yourself a big favor and quit trying to impress us.
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Old 01-29-2015, 08:01 PM   #26
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Dude, you're dealing with the very top electrician in northern va. You're just making yourself look silly. Fluke 434? That's a toy. He'll throw that in the trash can of the white house next time he's in there. Just do yourself a big favor and quit trying to impress us.

Yeah I know. It worked well for what I used it for.

There is much better stuff out there, But I don't get involved in it much any more.
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Old 01-29-2015, 08:08 PM   #27
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Yeah I know. It worked well for what I used it for.

There is much better stuff out there, But I don't get involved in it much any more.
That's cool. I'm sure it's a good tool. I just wanted to take up for my buddy! Lol
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Old 01-29-2015, 10:02 PM   #28
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Quote:
Originally Posted by Helmut View Post
I will rephrase.

Harmonic current does not flow on nuetrals in single phase 240/120V systems. All the harmonics cancel themselves out. They can not circulate in the transformer windings.

Running "super nuetrals" because of harmonic currents, is a waste of wire.

Please show me a screen shot of a single phase system nuetral with excess current flowing on it, because of harmonic currents.

If you want to trade screen shots of harmonics on 3 phase 208V systems, I'll try to check in more often as I have plenty taken with my fluke 434.

I NEVER said it was additive, I said it is possible to have harmonics in a 120/240 system. YOU SAID harmonics were not in a 120/240 system.


Quote:
Quote:
Originally Posted by Helmut View Post
There are no harmonics in a 120/240V system, which is why they are used for applications where harmonic producing equipment is used.

Oversizing neutrals is a waste of money.
I also said

IN 95% of the cases I have seen it used it is an over sell of copper.


An extreme example of current harmonics resulting in voltage distortion.



This was on a generator with an elevator drive phase to phase at 480 VAC

Last edited by Bad Electrician; 01-29-2015 at 10:35 PM.
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Old 01-30-2015, 01:00 AM   #29
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Any non linear load will generate current harmonics. Single or three phase is irrelevant. Voltage distortion is a result of current distortion combined with a power source that is not stiff enough.

Some harmonics propagate to the neutral, some don't. The ones that do want to flow back to the neutral point on the transformer. The grounding of that neutral plays no real role in the equation, except that there is an indirect relationship between harmonics and common mode current, but thats way outside the scope of this thread.

Short version: How you bond the neutral will not change the harmonic content of the power system.

Last edited by KennyW; 01-30-2015 at 01:03 AM.
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Old 01-30-2015, 07:15 AM   #30
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Originally Posted by KennyW View Post
Any non linear load will generate current harmonics. Single or three phase is irrelevant. Voltage distortion is a result of current distortion combined with a power source that is not stiff enough.

Some harmonics propagate to the neutral, some don't. The ones that do want to flow back to the neutral point on the transformer. The grounding of that neutral plays no real role in the equation, except that there is an indirect relationship between harmonics and common mode current, but thats way outside the scope of this thread.

Short version: How you bond the neutral will not change the harmonic content of the power system.
Winner, Winner, the short and to the point explanation.
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