RE: toroid quesion

["Tesla list" <tesla-at-pupman-dot-com>]

Original poster: "John H. Couture by way of Terry Fritz <twftesla-at-qwest-dot-net>" <couturejh-at-mgte-dot-com>


Godfrey -

For a quick and cheap equation I somtimes use

     pf = .8xd + .85xD

   Size       Bert     Exact     Quick
   5 x 2      5.34     5.91      5.85
   8 x 3.5    8.28     9.60      9.60
 100 x 8     80.66    90.76     91.40
  16 x 2     15.14    15.62     15.20

There are many other toroid equations that will give varying accuracies for
the toroid capacitance. It must be noted, however, tnat the toroid
capacitance is reduced when placed on the secondary coil. Finding this
actual capacitance is a real challenge for coilers.

John Couture

------------------------

-----Original Message-----
From: Tesla list [mailto:tesla-at-pupman-dot-com]
Sent: Sunday, January 20, 2002 9:42 PM
To: tesla-at-pupman-dot-com
Subject: toroid quesion


Original poster: "Loudner, Godfrey by way of Terry Fritz
<twftesla-at-qwest-dot-net>" <gloudner-at-SINTE.EDU>

Hi All

I did some calculations tonight to compare values of Bert Pool's formula and
the exact formula for the capacitance of an isolated toroid. Let D and d
denote the width and thickness respectively of a toroid. The results of some
randomly chosen values are given below.

D = 1", d = 0.4", C(bert) = 1.06746pF, C(exact) = 1.18129pF

D = 5", d = 2",    C(bert) = 5.33731pF, C(exact) = 5.90647pF

D = 8", d = 3.5", C(bert) = 8.27814pF, C(exact) = 9.60177pF

D = 100", d = 8", C(bert) = 80.6557pF, C(exact) = 90.7548pF

Here are the values for a toroid that sold on ebay tonight for $175.

D = 16", d = 2",  C(bert) = 15.1408pF, C(exact) = 15.615pF


------------------------  snip

Godfrey Loudner