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Re: Space winding
[kch] See my comments interspersed below.
On Sun, 13 Aug 2000 15:46:59 -0600 "Tesla list" <tesla-at-pupman-dot-com>
writes:
> Original poster: "Malcolm Watts" <M.J.Watts-at-massey.ac.nz>
>
> Hi Ken,
> I think I spot a problem:
>
> On 11 Aug 00, at 18:25, Tesla list wrote:
>
> > Original poster: "Kennan C Herrick" <kcha1-at-juno-dot-com>
<snipped>
[Referencing] the tabulation & commentary given recently by Mark
> S.
> > Rzeszotarski:
>
> <snip>
> > Now...my comments:
> >
> > 1. Secondary Q = wL/R where w=2 x pi x resonant frequency, L =
> > inductance & R = effective resistance. Also, L is proportional to
> n^2,
> > the square of the quantity of turns, other coil-shape factors
> being
> > equal.
> >
> > 2. From the tabulation, R diminishes, due to diminished
> > proximity-effect, by 1/2 for a tabulation-"w" of 0.5; that is, for
> the
> > case where the space between turns = the wire diameter.
> >
> > 2.1 But for that case, n has diminished to 1/2 of the prior
> quantity and
> > so L diminishes to (1/2)^(1/2) or .25 and also, ohmic R diminishes
> by 1/2
> > since the total wire length is 1/2 of what it was.
>
> Why should n have diminished? Are we not talking about the
> same number of turns?
[kch] Well, that may be the case; I had assumed without thinking about it
(not knowing the source of the table) that the coil shape & size and the
wire-size stayed the same, in which case the turn quantity would vary.
But maybe the coil size is assumed to change in order to accomodate the
same turn-quantity. Which is the case?
>
> > 2.2 Thus, it would seem, total effective R will have diminished
> to 1/2 x
> > 1/2 = 1/4 of that for the close-wound case. And thus, the new Q
> becomes
> > 0.25/0.25 of the old Q, or just the same.
>
> I have a set of measurements which shows that for the same
> diameter, height and number of turns, a spacewind produces a
> higher Q coil. I put them to the list about give years ago.
[kch] See my later correction to my posting.
<snipped>
Ken Herrick
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