From: mystuffs@orwell.net (Metlicka Marc)
Date: Tue, 26 Dec 2000 02:16:35 -0500
Subject: Re: [TSSP] Capacitance between primary and secondary
paul, terry, all
in the discrepancies between terry's c and Paul's calculated c values i noticed
in terry's pictures that his meter was setting on the primary itself. could
this be causing an added c to the 0 height value, and then also at the 15"
height difference, the meter may be pulling c and therefor causing a less then
calculated value? maybe a test using two meters, one connected with longer
leads and placed away and then trying a measurement with the first meter in the
field and then out of the field could show something?
marc
Paul wrote:
> Terry Fritz wrote (on tesla list):
>
> > I retook the physical measurements of my coil and measured the
> > capacitance from primary to secondary.
> >
> > I have the center of the primary plane 16.875 inches off the floor.
> > The inner primary radius is 5.95 inches.
> > There outer radius is 13.38 inches.
> > The primary tubing diameter is 0.252 inches.
> > There are 19.563 primary turns.
> > The secondary is still 10.25 x 30.0 inches.
> > There are 1000.5 turns
> > The secondary wire is 0.0201 inches in diameter.
> > The split 6 leg foil ground plane is on the floor but it is not connected
> > to anything.
> > The primary and secondary are floating.
> > My primary and secondary spiral (out and up) in the same direction.
> >
> > Pictures at:
> > http://hot-streamer.com/TeslaCoils/Temp/acmi1.jpg
> > http://hot-streamer.com/TeslaCoils/Temp/acmi2.jpg
> >
> > The primary to secondary capacitance measures:
> >
> > Height (inches) Capacitance (pF)
> > 0 42.2
> > 1 36.4
> > 2 33.7
> > 3 29.4
> > 4 27.6
> > 5 25.8
> > 6 23.6
> > 7 22.6
> > 8 21.8
> > 9 21.1
> > 10 19.8
> > 11 19.4
> > 12 19.0
> > 13 18.5
> > 14 18.0
> > 15 17.6
>
> Terry, I fed your dimensions into the new capacitance matrix
> generator, for the height 0 and height 15 cases.
>
> For height 0 I get the direct physical cap matrix elements:
>
> primary to groundplane: 24.0 pF
> primary to secondary: 26.7 pF
> secondary to groundplane: 22.5 pF all +/- 3%
>
> so the measurement between primary and groundplane will read
> the total capacitance as given by
>
> 26.7 | ( 22.5 # 24.0) = 26.7 | 11.6 = 38.3pF
>
> where | means 'in parallel with' and # means 'in series with'.
> I guess your presence in the field will have added a little more
> parasitic capacitance to bring the reading up to the measured value.
>
> The corresponding predictions for the 15" position are
>
> primary to groundplane: 27.1 pF
> primary to secondary: 5.9 pF
> secondary to groundplane: 28.2 pF all +/- 3%
>
> which gives a measurement of
>
> 5.9 | (27.1 # 28.2) = 19.7 pF,
>
> a little high of your 17.6 reading - not sure why.
>
> These capacitances are significant sizes and will have to be taken
> into account in the tssp simulator when primary coupling is
> introduced, although for acmi I should think they can be safely
> ignored.
>
> You might like to know that the new cap program generated the full
> distributed capacitance matrix for these two coil positions in a
> little under 15 minutes - quite an improvement in performance,
> which brings the prospect of being able to model a large number of
> coils that much closer.
>
> Cheers,
> --
> Paul Nicholson,
> Manchester, UK.
> --
Maintainer Paul Nicholson, paul@abelian.demon.co.uk.