RE: Toroids and capacitors

Dr. Res and all,

This brings up a good question a number of us have spoken about. Is the
major diameter of a torus measured to the outside edges (as is commonly
suggested) or should it be measured through the centerline of the minor
diameter (chord)?

My metalworking references and Machinery's Handbook (15th edition, page 162)
show torus measurements through the centerline of the minor diameter.
Example: A 8"x2" torus would have an overall width of 10" and a minor
diameter of 2".

I've back calculated the topload capacitance's of a number of coils by using
the measured frequency of the secondary with and without the torus. The
measurements always show a capacitance much lower than the programs predict
(using the common way of measuring a torus that is). Actual values are much
closer to program predictions when using a major diameter measured through
the centerline of the minor diameter. I've tested this on torus from 10" to

Your mileage may vary...

Brian Basura

-----Original Message-----
From: Tesla List [mailto:tesla-at-pupman-dot-com]
Sent: Wednesday, October 06, 1999 6:58 AM
To: tesla-at-pupman-dot-com
Subject: Re: Toroids and capacitors

Original Poster: "Dr. Resonance" <Dr.Resonance-at-next-wave-dot-net> 

One is the minor diameter measured across the "tube" section.  The second is
the major diameter which is measured from outer edge to outer edge (imagine
you sliced a sphere in half and measured it's cross sectional diameter ---
same applied to torus).


Dr. Resonance