RE: double wound secondary (fwd)

["Tesla list" <tesla@xxxxxxxxxx>]

---------- Forwarded message ----------
Date: Thu, 4 Oct 2007 08:07:24 -0500
From: Terry Oxandale <Toxandale@xxxxxxx>
To: Tesla list <tesla@xxxxxxxxxx>
Subject: RE: double wound secondary (fwd)

Interesting discussion. When I used to test protection and control
schemes for the local utility, If I couldn't obtain a high enough
current to pass through the CT, I would start twisting the supply cable,
and the tighter the cable was twisted together, the greater the
resulting current (with no other changes). I deduced this was because
these cables were opposite polarity (one feed and one return), and that
the mutual inductance was reducing overall impedance in the circuit. Now
if both cables were of the same polarity, would the opposite be true
(tightly wound cable increasing the total impedance?)?

Terry



-----Original Message-----
From: Tesla list [mailto:tesla@xxxxxxxxxx] 
Sent: Wednesday, October 03, 2007 3:46 PM
To: tesla@xxxxxxxxxx
Subject: Re: double wound secondary (fwd)


---------- 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=Q
B
>>>RE
>>>
>>>
>>>
>>>
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