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Re: Formula for true self capacity of a coil.



Hi all,

All the theoretical results are remarkably close to the measured values
considering  the approximations.

I.e Cmed/lumped should only be valid with a very large top load, Jones/Cox
has no end effects, internal C, wire diameter or c and E-Tesla5 uses a
strange (to me) weighted C in a lumped equation which is not applicable. I
bet John C,s has some  approximations too.

With a top load, my vote is for E-TeslaTM1 which would include complex
refection coefficients accurate intrinsic C of the coil and topload and even
C and M end effects with  small corrections for internal C, wire diamter, c
and local ground resistivity if you want to be really accurate. It would
also accurately predict the top voltage too.

Thanks again to Gavin for supplying the Cox equation for intrinsic(true) C
an invaluable addition to our formula library and equal to Wheeler L.

Regards Bob (Robert Jones)


-----Original Message-----
From: Tesla List <tesla-at-pupman-dot-com>
To: tesla-at-pupman-dot-com <tesla-at-pupman-dot-com>
Date: Monday, May 29, 2000 8:26 PM
Subject: RE: Formula for true self capacity of a coil.


>Original Poster: Terry Fritz <twftesla-at-uswest-dot-net>
>
>Hi John, All,
>
>Let's not loose sight of the "actual" measurements!
>
>1. 394.5 kHz
>2. 269 kHz
>3. 212.7 kHz
>
>I ran these through E-Tesla5 and got:
>
>1. 412.5
>2. 286.1
>3. 201.8
>
>and Cmed got:
>
>1. 401.43
>2. 298
>3. 230.41
>
>and Jones/Cox got:
>
>1. 397.07
>2. 296.678
>3. 208.78
>
>and John C. got:
>
>1. 403.6
>2. 299.58
>3. 231.38
>
>"We" all came out high on the second one compared to the actual...  Dare I
>suggest that the second actual could be a little wrong! =:O
>
>It would be a scarry day when we trust the calculations over the actual
>measurements but...  In my own testing I kept getting high numbers in one
>test.  I went back and check the "actual" dimensions and... oops!  The darn
>computer WAS right! ;-))
>
>It "slightly" seems that Jones/Cox is getting the best answers...  Of
>course, slap dual toroids on these coils, and I'll vote for E-Tesla5 ;-)))
>
>Hey!  Does anyone remember the "good ol' days" when we had no clue what a
>given secondary system frequency would turn out as ;-))
>
>Cheers,
>
> Terry
>
>BTW - Great work Gavin in finding that true C formula!!
>
>
>
>At 03:35 PM 5/29/00 -0700, you wrote:
>>
>>Gavin -
>>
>>You may be interested in how your calcs compare with the JHCTES Ver 3.1
>>program.
>>
>>Coil    Parameter     Gavin         JHCTES
>>
>># 1       L           17.87         17.87
>>          Cmed         8.8           8.9
>>          fr kHz     401.43         403.6
>>
>># 2       L            29.3          28.82
>>          Cmed          9.9           9.79
>>          fr kHz      298.00        299.58
>>
>># 3       L            42.25         42.67
>>          Cmed         11.19         11.09
>>          fr kHz      230.41        231.38
>>
>>Very good agreement considering different equations were used.
>>
>>John H. Couture
>>
>>----------------------
>>
>>-----Original Message-----
>>From: Tesla List [mailto:tesla-at-pupman-dot-com]
>>Sent: Monday, May 29, 2000 11:27 AM
>>To: tesla-at-pupman-dot-com
>>Subject: Formula for true self capacity of a coil.
>>
>>
>>Original Poster: "Gavin Dingley" <gavin.dingley-at-astra.ukf-dot-net>
>>
>snip....
>
>