Re: double wound secondary (fwd)

["Tesla list" <tesla@xxxxxxxxxx>]

---------- Forwarded message ----------
Date: Thu, 4 Oct 2007 03:42:36 +0800
From: Peter Terren <pterren@xxxxxxxxxxxx>
To: Tesla list <tesla@xxxxxxxxxx>
Subject: Re: double wound secondary (fwd)

Something intuitively seems wrong here with a double wound coil having 4 
times the inductance.  I don't know the math but I thought that a wide 
conductor had a lower inductance. This surely would be the extreme case of n 
parallel inductors. Don't forget that it is not the same current that passes 
through both coils in parallel (as in a series arrangement when by the 
square of twice the number of turns then you would have 4 times the L).
My guess is that inductance does not significantly change with two parallel 
closewound coils connected in parallel. Otherwise Litz wire would have a 
phenomenal increase in inductance.

Peter
http://tesladownunder.com

> ---------- Forwarded message ----------
> Date: Tue, 02 Oct 2007 01:18:56 -0700
> From: Barton B. Anderson <bartb@xxxxxxxxxxxxxxxx>
> To: Tesla list <tesla@xxxxxxxxxx>
> Subject: Re: double wound secondary (fwd)
>
> Hi Dave,
>
> The Q isn't as neat (in my little book) as the inductance. The only way
> possible I can account for this is if the two windings at the bottom and
> top are in parallel and very close proximity. We know inductors in
> parallel add. But, when current is flowing and if the two inductors are
> in "that" type of proximity (and position) winding for winding, then we
> now have the currents in both inductors doubling up on the flux (the
> density is double on both windings). This would certainly result in a 4x
> (or about) inductance. I've never done that with a coil, but from an arm
> chair physics view, it makes perfect sense that you would have 4X the L.
>
> One of the goofy things not always realized with the multiturn coil
> formula's (air core or otherwise) is that that a series connection is
> assumed. You must have 2 parallel wires in this type of close proximity
> to achieve this. Very cool!
>
> Take care,
> Bart
>
>>---------- Forwarded message ----------
>>Date: Tue, 02 Oct 2007 01:32:13 +0000
>>From: sparktron01@xxxxxxxxxxx
>>To: Tesla list <tesla@xxxxxxxxxx>
>>Subject: RE: double wound secondary (fwd)
>>
>>Antonio
>>
>>Gary Weaver has posted several times (and I have built) a "multiple layer"
>>coil that is not specifically a bifilar wound coil.  Wind one layer _close
>>wound_ then wind another layer on top of and in "groves" between adjacent
>>turns of lower winding layer.
>>
>>By careful arrangement of individual wire entrance and exit into windings,
>>maximum winding error of only +/- 1 turn (much less is practical) will
>>occur.
>>
>>I have wound such a coil with two layers, and have noticed a MUCH higher Q
>>then a typical "bifilar" wound coil.
>>Inductance is ~4X higher to boot.  In this case, it is equivalent of two
>>coils close wound in parallel, R would approach
>>R/2 (proximity effects will make it larger, but still significantly less R
>>then a single winding coil).
>>
>>Band pass testing with two winding coil revealed a bandpass so narrow, I
>>could not fine tune VFO to maximum response, it would "jump" either side 
>>of
>>response peak.  Gary noticed large improvement with two windings in
>>parallel, less improvement from 2 to 3 layers in parallel.
>>
>>My coil was used on a VTTC powering a CO2 laser.
>>
>>Regards
>>Dave Sharpe, TCBOR/HEAS
>>Chesterfield, VA. USA
>>
>> -------------- Original message ----------------------
>>From: "Tesla list" <tesla@xxxxxxxxxx>
>>
>>
>>>---------- Forwarded message ----------
>>>Date: Mon, 1 Oct 2007 10:06:33 -0400
>>>From: Scott Bogard <teslas-intern@xxxxxxxxxxx>
>>>To: Tesla list <tesla@xxxxxxxxxx>
>>>Subject: RE: double wound secondary (fwd)
>>>
>>>
>>>Thanks guys,
>>>     I understand much better now.
>>>Scott Bogard.
>>>
>>>
>>>
>>>>Date: Sun, 30 Sep 2007 08:35:57 -0600
>>>>From: tesla@xxxxxxxxxx
>>>>To: tesla@xxxxxxxxxx
>>>>Subject: Re: double wound secondary (fwd)
>>>>
>>>>
>>>>---------- Forwarded message ----------
>>>>Date: Sun, 30 Sep 2007 11:06:50 -0300
>>>>From: Antonio Carlos M. de Queiroz <acmdq@xxxxxxxxxx>
>>>>To: Tesla list <tesla@xxxxxxxxxx>
>>>>Subject: Re: double wound secondary (fwd)
>>>>
>>>>Tesla list wrote:
>>>>
>>>>
>>>>>---------- Forwarded message ----------
>>>>>Date: Sat, 29 Sep 2007 18:24:54 -0400
>>>>>From: Scott Bogard <teslas-intern@xxxxxxxxxxx>
>>>>>To: tesla@xxxxxxxxxx
>>>>>Subject: double wound secondary
>>>>>
>>>>>
>>>>>Hey everybody,
>>>>>     I know, this topic has been covered an awful lot in the
>>>>>archives, I looked; but there seems to be some disagreement,
>>>>>weather it is good or bad.  It seems lately, everybody now thinks
>>>>>it is not such a bad idea, as it decreases the resistance,
>>>>>therefore increasing output.  But, from what I know of formulas
>>>>>and such, two inductors (since a coil is essentially an
>>>>>inductor) in parallel decreases the inductance, which should
>>>>>decrease voltage out?  Does this situation not apply with a
>>>>>transformer, or does the resistance decrease make that much of a
>>>>>
>>>>>
>>difference to make up for it?
>>
>>
>>>>>Or, does nobody actually know why it works so well?  Just curious
>>>>>(and considering double winding my 6-in secondary). Scott Bogard.
>>>>>
>>>>>_________________________________________________________________
>>>>>
>>>>>
>>>>Two coupled inductors in parallel, with bifilar winding and high
>>>>coupling (M=sqrt(L1*L2)), act as a single inductor with L=L1=L2=M.
>>>>The proof is easy.
>>>>It remains to be seen if the loss is smaller than when using a
>>>>single wire with the same area of the two wires used in the bifilar
>>>>
>>>>
>>winding.
>>
>>
>>>>You can probably use a simulator as Javatc, that calculates wire
>>>>losses, considering a single coil with the total number of turns
>>>>with the two wires, and then divide the resulting resistance by 4 to
>>>>obtain the resistance of the bifilar coil. Compare then with what
>>>>happens with a wire with doubled area and single winding. In
>>>>principle, I would expect similar results, or advantage for the
>>>>single wire winding because there would be space between the turns,
>>>>
>>>>
>>reducing the proximity effect, if the winding length is kept.
>>
>>
>>>>Note that using the same winding length you can use a wire with
>>>>twice the diameter, and so four times the area. The losses must be
>>>>smaller in this case.
>>>>
>>>>Antonio Carlos M. de Queiroz
>>>>
>>>>
>>>>
>>>>
>>>>
>>>_________________________________________________________________
>>>Explore the seven wonders of the world
>>>http://search.msn.com/results.aspx?q=7+wonders+world&mkt=en-US&form=QB
>>>RE
>>>
>>>
>>>
>>>
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