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Re: Isotropic secondary capacitance
From: DR.RESONANCE[SMTP:DR.RESONANCE-at-next-wave-dot-net]
Sent: Monday, September 08, 1997 11:43 AM
To: Tesla List
Subject: Re: Isotropic secondary capacitance
To: Malcolm
If you measure the Fres of one of your coils, then measure its inductance,
does this calculated value of Cdist agree with the value you would obtain
by solving the Fres (equation for resonance) for capacitance? In one of
your coils, how close is the measured value (in % margin or error)? Does
it vary much between PVC insulated wire and magnet wire?
DR.RESONANCE-at-next-wave-dot-net
----------
> From: Tesla List <tesla-at-pupman-dot-com>
> To: 'Tesla List' <tesla-at-poodle.pupman-dot-com>
> Subject: Re: Isotropic secondary capacitance
> Date: Sunday,September 07,1997 10:51 PM
>
>
> From: Malcolm Watts[SMTP:MALCOLM-at-directorate.wnp.ac.nz]
> Sent: Sunday, September 07, 1997 5:05 PM
> To: tesla-at-pupman-dot-com
> Subject: Re: Isotropic secondary capacitance
>
> Hello Jim,
>
> > From: bmack[SMTP:bmack-at-frontiernet-dot-net]
> > Sent: Saturday, September 06, 1997 10:07 PM
> > To: tesla list
> > Subject: Isotropic secondary capacitance
> >
> > Fr Tom,
> >
> > A very astute observation on the nature of distibuted
> > capacitance animal! That surface area capacitance could
> > calculated(?) using the "free air capacitance" equation for
> > the coil area and the standard "plate equation" with curvature
> > of the wire considered, to find the inter winding capacitance.
> > Am I on track here?
> >
> > Now, are these two entities in parallel or series with respect to
> > each other? Maybe a little of both? Ouch!
> >
> > When I run very low power tests to tweek the systems, placing ones
> > hand near the coil body has as much effect on the resonance as getting
> > near the top cap. This in my opinion clear evidence of isotropic
activity.
> >
> > With a little help from our friends, there might even be a way to
reliably
> > predict the distributed capacitance mathematically!
>
> There is indeed!! You'll be pleased to know that after a three month
> search while researching a TC article for a magazine, I found it. It
> is Medhurst's formula:
>
> C = HD pF where D is coil diameter in cm and H is a factor that
> follows the law:
> h/d = 2 H = 0.51
> h/d = 5 H = 0.81
> Interpolation is linear for this h/d range. H bottoms out at 0.46 for
> an h/d = 1 (which as fate would have it was the final form Tesla's
> extra coil took :) The tabulated values for H remove the complex
> mathematics from the formula.
>
> Malcolm
>
>