Re: Inductance calculations

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

Original poster: "Antonio Carlos M. de Queiroz by way of Terry Fritz <teslalist-at-qwest-dot-net>" <acmq-at-compuland-dot-com.br>

Tesla list wrote:
 >
 > Original poster: "Godfrey Loudner by way of Terry Fritz 
<teslalist-at-qwest-dot-net>" <ggreen-at-gwtc-dot-net>
 >
Hello Godfrey
 >
 > If its conveniant, can you please make a posting of the formula
 > used in the Maxwell method for the primary inductance. I've
 > upgraded my adobi, so the computer will translate now. I'm going
 > to have to order Maxwell's books from Dover press.

I prepared a text:
http://www.coe.ufrj.br/~acmq/tesla/maxwell.pdf
I can't upload it to my site now (some problem there), but will try
again later.
A French translation of Maxwell's book is available at gallica.bnf.fr
(go to the "recherche" page and look for Maxwell in the books in
image format).
The integral is at item 701. The inductance calculation method is at
item 693. This edition has also some interesting comments by the
translator. More useful than the original.

Another observation:
When I try a flat coil with 1 turn (the same 0.5 m of diameter and
wire with 0.002 m of diameter, but height=0), I get:
Inca: 0.0041117500 mH (elliptic functions)
       0.0041117517 mH (numerical integration, 8000 segments)
(I had to improve the calculation of the elliptic functions to
make the calculations agree.)
Fantc calculates 4.11175 uH, exactly what my integral gives.
Grover's formula for a 1 turn coil gives 0.0052109908 mH
Maxwell's formula for 1 turn coil (adapting [705] in the book)
gives 0.0041154403 mH.
With 1 turn, but 20 cm of height, Inca obtains by numerical
integration L=0.0041006707 mH. Seems ok.
The "coil" program gives 4.067 uH.
Fantc obtains: 1.57401 uH. Seems too little.
Acmi obtains: 1.58 uH, same problem, and 4.55 uH with a flat loop.

Antonio Carlos M. de Queiroz