Re: double wound secondary (fwd)

["Tesla list" <tesla@xxxxxxxxxx>]

---------- 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
>>>
>>>
>>>
>>>      
>>>
>>_________________________________________________________________
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