RE: double wound secondary (fwd)

["Tesla list" <tesla@xxxxxxxxxx>]

---------- 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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