Re: Inductance calculations

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

Original poster: "Barton B. Anderson by way of Terry Fritz <teslalist-at-qwest-dot-net>" <classictesla-at-netzero-dot-com>

Hi Antonio,

Ok, checking "Maxwell L" and "Elliptic fun" I get 45.96uH. I downloaded, 
unzipped, and ran Steve Moshier's coil program. There certainly is 
consistency between programs for the inductances identified. I ran each, 
changing only heights to get a few rows of data ( r1r2=.5m, wd=.002m, t=5).

ht      Fantc   Acmi    MandK  |  Inca     Moshier
0.2m    39.35   39.32   39.44  |  45.96    46.38
0.5m    25.87   25.84   25.93  |  35.29    35.74
0.75m   20.45   20.43   20.50  |  31.11    31.60
1.0m    16.96   16.93   16.99  |  28.48    29.04

Maybe Paul can identify what is going on. Moshier's c-source is included 
and appears well written and documented with referecences. I ran geometry 8 
(Single-layer circular helical solenoid of round wire). coil.c points for 
geo 8 points to "helsol" located in "formulae.c". There, Moshier references 
Chester Snow '1952. I'm looking for papers on C. Snow but I'm not finding 
much other than references. Somethings wrong on one side of the line or the 
other if all are representing the same inductance inclusions.

Bart

Tesla list wrote:

>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: "Barton B. Anderson by way of Terry Fritz 
> <teslalist-at-qwest-dot-net>" <classictesla-at-netzero-dot-com>
> >
> > Hi Antonio,
> >
> > I ran Inca v1.0e- 11/3/2003 and obtained the following primary inductance
> > in question:
> >
> > n1= 5.00; h1= 0.20; r11= 0.50; r12= 0.50; b1= 0.00 (wd doesn't print to
> > screen, but was 0.002)
> > Primary inductance L1:    0.0379600169 mH
>
>This is Wheeler's formula. Check the boxes for "Maxwell L" and
>"Elliptic fun.".
>The site below has a program "coil" that the author says that is
>accurate:
>http://www.moshier-dot-net/coildoc.html
>Its calculation for solenoids gives also the 46 uH.
>Lundin's formula gives 39 uH.
>Mandk also gives 39 uH.
>I see that discrepation between Maxwell and the others appears when
>the number of turns is small. But Maxwell's formula is based on
>single turns?! The problem is not a consequence of not considering
>an helix, because my numerical integration considering the helix also
>gives 46 uH.
>
>A test, to see if the results are consistent:
>If I stack two identical coils, the total inductance must be 2L+2M.
>
>With Inca:
>L=45.9691043 uH
>M=18.6011663 uH
>2L+2M=129.1405412 uH
>Calculating the inductance of a coil with 40 cm of height and 10 turns:
>Ltotal=129.1411539 uH
>(The "coil" program gives 130 uH)
>
>With Fantc:
>L=39.37069 uH
>M=18.68313 uH
>2L+2M=116.10764 uH
>Ltotal=116.1666 uH
>
>So both are consistent... Some program is doing something funny...
>I will continue to check the program. Maybe I can build that 1 meter
>coil to check.
>
>The Inca program is in http://www.coe.ufrj.br/~acmq/programs
>
>Antonio Carlos M. de Queiroz
>
>
>
>