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Re: Primary inductance



Subject:     Re: Primary inductance
      Date:  Wed, 07 May 1997 11:54:06 -0700
      From:  "Rick L. Kirby" <rkirby-at-earthlink-dot-net>
        To:  Tesla List <tesla-at-pupman-dot-com>
       CC:   rkirby-at-earthlink-dot-net
References: 
           1


Tesla List wrote:
> 
> Subject:   Primary inductance
>   Date:    Mon, 5 May 1997 19:33:33 -0400 (EDT)
>   From:    ADatesman-at-aol-dot-com
>     To:    tesla-at-pupman-dot-com
> 
> I'm having some difficulty measuring the inductance of my primary coil -
> I
> think because of old and crotchety test equipment, but maybe it's just
> stupidity.  At any rate, I'm wondering - I have 13 turns of 1/4" copper
> tubing on a 30 degree bank, spreading out from 6 inches to about 25
> inches.
>  Does anybody with a similarly-sized primary know its inductance?  (I am
> just
> trying to get a benchmark, to see where the problem might lie.)
> Thanks!!
>    Aaron Datesman

Aaron
        I use the following formula:

         2     2
        A  X  N
  L= -----------------
       8A  +  11W

Where:

  L= inductance in microhenries.
  A= average radius in inches as measured from the central
     axis to the middle of the winding.
  N= number of turns in the winding.
  W= width of coil winding on one side in inches.

                  center axis
                        |
                        |
         o o o o o      |      o o o o o    <---- coil cross section
                        |
             |----a-----|      |---w---|
                        |

 Note: This will get you in the ballpark for flat or 30 deg. styles.
       I calculate 64-65 uh for yours if I visualized yours right.
       You can also download several programs and spreadsheets to
       do this for you.
       
       from: ftp://nic.funet.fi/pub/sci/electrical/tesla/
             and its sub directories.

safe coiling
Rick Kirby