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FW: Isotropic secondary capacitance


From: 	Malcolm Watts[SMTP:MALCOLM-at-directorate.wnp.ac.nz]
Sent: 	Wednesday, September 10, 1997 12:13 AM
To: 	tesla-at-pupman-dot-com
Subject: 	Re: Isotropic secondary capacitance

Hello Dr RESONANCE,
 
> 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? 

Medhurst agrees with the resonance and lumped-L check I've done on 
_all_ coils I've wound to well within 5%. (2% in a majority of cases).
In short, yes. The real battle in finding a formula that worked was 
in defining the essence of Cself. Of course one runs into interturn
capacitance for _ungrounded_ coils which was thrown out because it 
failed to work for a grounded upright single-layer coil. Medhurst 
applies strictly to this particular case.
    The artificial model I came up with forces both current and 
voltage distribution to match this case (until it is refuted by a 
better one of course :)

> 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? 

I have found no case yet where Cself depends on the insulation. As I 
say, all my research suggests the _overall effect_ of Cself is 
isotropic. To get a feel for its true nature, I refer you to the 
Corum's series of diagrams showing the progression from cavity to 
open resonator. Picture the C distribution of the line wrt to its 
surroundings in all those cases and you see Cself :)

Regards,
Malcolm 
<snip>
> > 
> > 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
> > 
> > 
> 
> 
> 
>