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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
--------------------------------
-----Original Message-----
From: Tesla list [mailto:tesla-at-pupman-dot-com]
Sent: Saturday, November 24, 2001 12:30 PM
To: tesla-at-pupman-dot-com
Subject: Re: 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 J.B.,
I'm using a rq/tcbor triggered arrangement. I think we are still
beta-testing (I know I am). I'm using a basic
circuit without resistors. I don't have much variation with the controller
which I mounted on the control panel
and left the rest under the coil. I think the pot used should be about 50k.
My controller came with a 250k pot
and I haven't tried a 50k yet. My controller doesn't have a diac to fire
the triac gate, but I intend on
throwing one in. My controller is not a Lutron, but one I picked up from
ACE Hardware. Same basic circuit
however minus the diac. I put in a 25A triac.
Regarding performance? Not sure yet. At this point, the srsg out-performed
the trigger gap. But for me, it's
too soon to make a judgement. The trigger gap however is running sweet and
cool, and this gap isn't any louder
than my srsg.
I took some photo's a couple weeks ago and through them up showing the
gap, coil, and sparks. I'm running at
less than half power in the garage due to a metal bed which is up on the
rafters and puts me in harms way (the
end of it is right over my head next to the control box and the other end
is about 5 feet to the toroid). I've
tried to keep it below this spark range.
http://www.classictesla-dot-com/photos/tgk/tgk.html
Take care,
--
Barton B. Anderson
http://www.classictesla-dot-com