Solid or stranded wire for motors on VFD's 2

[unwiredo]

Does it matter if the wire feeding a motor from a VFD is stranded or not. I would think the more strands the better.
This is relative to the same wire gauge for comparison.

The stranding gives more paths for the current to flow so the theory goes.

thanks

 

[DickDV]

For the second time, Skogsgurra has made a crucial point about this subject that has been largely ignored----THERE ARE NO HIGH FREQUENCIES IN TYPICAL DRIVE/MOTOR LEADS TO MAKE SKIN EFFECTS AN ISSUE!!!!!

This subject seems to have nine lives and has become almost comical.

Is anybody really thinking about this???????

 

[electricpete]

Dick, my friend. Who are you shouting at?



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[electricpete]

For the record, Dick.

I did not ignore it Skogsgurra's comments. I responded to comments which implied there would be absolutely no high frequency derating for solid conductors as opposed to stranded conductors.

Why do the high frequency users use Litz wire in their power transformers? Why do we use laminated busbars for high current high frequency equipment? Why do you think generator and transformer manufacturers go to the trouble of using expensive Roebel conductors? Because using plain conductors is boring? Because they have too much money?

They are conductors. One touches its neighbour, which in turn touches its neighbours. Thus they are all electrically in contact with each other over anything more than a few inches of cable. Do you need a picture to help explain that? In fact, don't take my word for it, try it with a multimeter and prove it for yourself.

Different ohmic resistances per unit length are due to differences in the cross section of copper in the conductor. I thought that would be pretty obvious.

And the last comment is somewhat ironic. As we know, stranded wire has higher dc resistance per unit length than solid conductor of the exact same circular mil cross section (or same weight) due to the very reason that there is an insulating effect between the strands (so the effective length of the conductor is longer since it has to spiral around following the strand instead of traveling straight).

I have the highest respect for the author of these comments. But in this case I believe he missed the mark and I was weighing in on the side of someone whose arguments I believe were unfairly criticized.

Do you think my comments were inappropriate?

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[itsmoked]

Yes. In many aspects including your sarcasm.


Keith Cress
kcress -

http://www.flaminsystems.com

 

[electricpete]

davidbeach, I doubt your claim that stranded wire has a beneficial effect at high frequencies simply due to the fact that, for skin effect to operate, the skin can't be shorted to anything else over its length. Clearly, a strand in the middle of a bundle has no "skin" since it is all shorted to adjacent conductors.

Or am I missing something here?

I guess your last question was a rhetorical one, since apparently you were so uninterested in the answer that you screamed at the people who gave it to you.

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[electricpete]

"In many respects." Wow. Are you reading the same thread I am? You are saying that DickDV was right and everyone who posted toward the end of this thread should should be belittled for not shutting up when he decided the thread was over? And I shouldn't have brought facts (a link and a handbook quote) into the discussion to address an apparent misconception on the part of multiple posters who believed stranded conductors have no beneficial effects for high frequencies? Including one poster who asked for feedback on this exact point? Is that what you are telling me?


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[ScottyUK]

ePete,

I appreciated the link, and it was mainly for my benefit I think. Thanks.

I am not 100% sold on the minimal contact betwen strands theory although I can see the reasoning behind that argument. I am pleased that you can back up what you are saying with some references. That puts you in a minority of one so far.

Assuming the lineal contact theory has some merit I was surprised at the very wide spread of results obtained by the researchers.


----------------------------------

If we learn from our mistakes I'm getting a great education!

 

[DickDV]

Well, shucks, guys. Time for me to apologize. I just get so frustrated over the tendency to press on in some of these threads even where there is no basis for doing so.

And, electricpete, I particularly appreciate and respect your comments in this forum. My shouting should not have been directed at you but at those who absolutely will not stop the discussion even in the face of data that says the issue is moot.

Again, my apologies.

 

[electricpete]

It was not my intent to make a big deal about the points I I had made earlier in my posts. But Dick's post put me in the mindset that I needed to justify why I had posted.

Perhaps I overreacted just a weeee bit to Dick's comments ;-)
Thanks guys for not over-reacting to mine.

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[electricpete]

And my apologies as well for over-reacting.

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[waross]

Don't forget that all stranded wire is not created equal. Some wire is constructed with clean strands. Some strands are tarnished. Depending on the type of insulation and the way in which it is applied to the conductor, some strands will stay clean and some will tarnish with age even inside the insulation. It doesn't take much tarnish on a strand to dramatically limit the current passing from strand to strand.
Tarnish not withstanding, I will still use stranded wire for motor connections with or without a drive.

Bill
--------------------
"Why not the best?"
Jimmy Carter

 

[Giz99]

Most cable manufactures will sell VFD Cable. This is the best option a the VFDs can create a lot of electric noise which can cause communication problems with equipment. I have seen issues with device communications.light curtains, and other equipment just because the proper cable and wiring practices were not followed.

GTiz.