RE: Bart's Coil

["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>


Bart -

Thank you for making the mutual inductance tests. It looks like the programs
are amazingly close to the test values. Your test values of 11.04 amps and
2.72 volts gives Lm = 653.52. The JHCTES gives 617.76 for Lm. I would expect
that the JHCTES value to be lower because this is for when the bottom of the
secondary coil is on the same level as the primary. When the secondary is
lowered the Lm and the K would become larger.

I plan to change the JHCTES program to include negative distance values in
the near future so comparisons can be made on an equal basis. I agree that
the K appears to be in the .159 and .169 range.

There is a relatively easy test that directly tests for the K factor and
eliminates the inaccuracies caused by the three variables, Lm, Lp, and Ls
when calculating K. This test only requires a function generator, frequency
counter, and oscilloscope and is shown in my TCC Guide page 14-11 of which I
believe you have a copy. The equation is

              K = sqrt(1-(Fo/Fs)^2)

The function generator is used to feed a signal into the primary coil. There
will be two resonant frequencies Fo and Fs when the unloaded (no toroid)
secondary coil is open (Fo) and when it is shorted (Fs). The two frequencies
are usually just below the loaded resonant frequency. The oscilloscope will
indicate the two frequencies. The test is sensitive to the surrounding
conditions.

 I have not tried this on a coil of your size but it works good on small
coils. I would be interested in the results if you get a chance to do this
test.

John Couture

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

-----Original Message-----
From: Tesla list [mailto:tesla-at-pupman-dot-com]
Sent: Sunday, November 25, 2001 12:27 PM
To: tesla-at-pupman-dot-com
Subject: Re: Bart's Coil (was How many STSG's in service?)


Original poster: "Barton B. Anderson by way of Terry Fritz
<twftesla-at-qwest-dot-net>" <tesla123-at-pacbell-dot-net>

Hi John,

I measured Mutual Inductance this morning as requested. 11.04A on primary
and
measured 2.72V across secondary. I did this a few times to ensure accuracy.
Values remained constant. Now, all this depends on measured inductances for
true accuracy, but I don't have an LCR handy (I know, shame on me).

Here is a comparison with ACMI, JavaTC, and JHCTES.

                    Mu           K          Ls             Lp
ACMI        628.9     0.1586    121.8        128.98
JavaTC      653.5     0.1665    121.33      126.9
JHCTES    653.5     0.1686    121.23      123.88

Note: JHCTES Mu above is calc'd by me from JHCTES Ls and Lp outputs, same as
with JavaTC's Ls and Lp outputs. ACMI Mu and K are pure program outputs. If
I
were to use ACMI's Ls and Lp outputs and run calc's based on my
measurements,
then Mu would be 653.52 and K would be 0.1649.

When I ran JHCTES 3.3 today, it asks for Sec. above Pri. In my case, the
secondary is "below" the primary, so the input should be (-1.25). JHCTES
defaults to zero (or appears to based on outputs).

So, with all that said, I'd say K falls somewhere between 0.159 and 0.169.
Really have to LCR it, to narrow it down.
--
Barton B. Anderson
<http://www.classictesla-dot-com>http://www.classictesla-dot-com

Tesla list wrote:
>
> Original poster: "John H. Couture by way of Terry Fritz
<twftesla-at-qwest-dot-net>"
> <couturejh-at-mgte-dot-com>
>
> Bart's coil is a beauty and it appears to follow the outputs of the JHCTES
> Ver 3.3 very well.  Click on
>
>       <http://home.att-dot-net/~couturejh/>http://home.att-dot-net/~couturejh/
>
> Enter for the 4 Primary inputs - Spiral
>   .042 - 11 - 0 - 11
> Enter for the 5 Secondary inputs
>   4.25 - 1721 - 42.73 - 28
>
> The outputs will be for the oper freq = 68.9 and the pri turns = 14.8
equal
> to Bart's coil specs.
>
> The output for the K factor = .157 assumes the sec and pri bottom turns
are
> at the same level. This appears to be a little high.
>
> With the mutual inductance test and 2.653 amps in the primary the voltage
> across the secondary coil will be about 617 millivolts (the mutual
> inductance). With the secondary 4 inches above the primary the voltage
would
> be 395 mv (mutual inductance) and K= .101
>
> Bart - I would be interested in the results if you ever make these test.
>
> John Couture
>