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Re: distributed capacitance measurement? Isotropic?
From: Malcolm Watts[SMTP:MALCOLM-at-directorate.wnp.ac.nz]
Sent: Monday, September 08, 1997 11:57 PM
To: tesla-at-pupman-dot-com
Subject: Re: distributed capacitance measurement? Isotropic?
Hi Fr. Tom, all,
I forgot to answer this bit....
> > Is there any correlation between distributed
> > capacitance and exposed wire surface? Or is it primarily an
> > inter-turn phenomenon? What does that have to say about the relative
> > merits of tight versus space windings? My own work has led me to
> > believe that the exposed surface area of a coil is very important,
> > especially in regard to the electrostatic phenomena that accompany
> > Tesla coil operation. Probably much greater in its overall EFFECTS
> > than the inter-turn capacitance. By the same token, the proximity of
> > the inside of the coil windings and the coil FORM result in
> > interactions that greatly affect the Q of a coil. The losses are
> > probably capacitive in nature, in that energy is capacitively coupled
> > to the material that makes up the form.
I measured a whole series of these with h/d's ranging from 0.5 to 5
about two years ago. Both sets of coils had the same winding pitch.
The highest Q's were obtained with h/d=1 for a spaced wind. I don't
remember all the details now. Close wound coils with h/d's of 2 to 4
or so seemed best with moderately large toploads. Plenty of capacitive
interaction going on between the load and the coil but little
inductive effect. I have actually slit toploads to check this and the
effect on inductance was negligible.
Malcolm