RE: Bart's Coil - The Toroid

["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>


To All -

I ran the numbers for this coil and found E-Tesla6 was within 1.2% of the
actual test data, very good. It will be interesting to see if this excellent
accuracy holds when other coils are tested and the data entered into the TC
programs.

           Test        E-Tesla6
  Ctot    43.91 pf     45.07 pf
  Fr      68.90 KHz    68.06 KHz

Have other coilers checked the data from Bart's coil with the   E-Tesla6
program?

The Ctot includes both the coil and toroid capacity so it was not possible
to check the reduction in toroid capacity.

John Couture

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-----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 - The Toroid


Original poster: "John H. Couture by way of Terry Fritz
<twftesla-at-qwest-dot-net>" <couturejh-at-mgte-dot-com>


To All -

Note below that the secondary terminal input (toroid) is 28 pf. This is the
true capacitance of the toroid when placed on Bart's TC. The toroid is 9" x
30" and has a calculated free space capacity of 33 pf. This reduction in
capacity when the toroid is placed on a TC is now known by coilers and it
varies depending on the TC and the surroundings. It appears the only way to
find this true capacitance is to build the coil and test it. With this data
you can then calculate the true capacitance.

To do the calcs there are four basic equations that have to be solved
simultaneously assuming 2 or more of the parameters are changed at the same
time. The four equations are:
     1. Wheeler equation
     2. Medhurst equation
     3. Frequency equation
     4. LpCp = Ls (Ccoil + Ctor) equation

All of the parameters involved in these equations can be determined at the
design stage except the toroid capacitance Ctor. After the TC is built and
tested the Ctor can be found. The  operating frequency found by test can be
used in the frequency and LC equations to find Ctor.

 Bart found the test operating frequency for his TC was 68.9 KHz. Using the
JHCTES program I adjusted the secondary terminal input (28) until the test
frequency (68.9) appeared in the outputs. This then made all of the program
parameters agree with the test parameters. It appears that this is a goal
more difficult for coilers to reach than long sparks.  These calculations
can be done by TC computer programs like the JHCTES program saving the TC
designer a lot of time and work.

There is a lot more to the design of Tesla coils but the most important
condition is that the TC must be in tune and that is what the above
accomplishes. For this condition you must know the true capacitance of the
toroid when it is placed on the secondary coil. Coilers in the past did not
know this and believed the calculations and programs did not work.

John Couture

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


-----Original Message-----
From: Tesla list [mailto:tesla-at-pupman-dot-com]
Sent: Saturday, November 24, 2001 8:07 PM
To: tesla-at-pupman-dot-com
Subject: RE: Bart's Coil (was How many STSG's in service?)


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/

Enter for the 4 Primary inputs - Spiral
  .042 - 11 - 0 - 11
Enter for the 5 Secondary inputs
  4.25 - 1721 - 42.73 - 0 - 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

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