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Re: Optimal toroid elevation
Hi Bart, Jeff, Marco,
There is a subtle detail here you need to be aware of.
As long as the torroid is raised a few inches above the top of the
secondary, the program should work fine. However, if you are setting the
toroid directly on top of the secondary, it is probably changing the
secondary coil's inductance. Try to remeasure the secondary's inductance
with the toroid in place as in Test #1 below. It will probably be about
10% lower than without the torroid in place. I did a quick test and my big
coil went from 75.4mH to 68.9mH (about an 8.6% drop in inductance) The
torroid is messing with the secondary's inductance since it is so close.
In a normal coil, the little distance between the top of the secondary and
the toroid provides enough isolation. However with them in almost direct
contact, the secondary inductance will change. Since E-tesla does not
account for this inductance variation, it will not give the best answer.
This may also be a problem if you have a corona ring on the top of the
secondary but I "think" that ring should have a split in it which should
fix the problem??
I think if you use the new measured value of inductance, E-Tesla will give
the right answer. However, the very close large metal toroid may alter the
voltage distribution a bit?.? I really don't know for sure.
BTW Marco, E-Tesla does "try" to find the "true" volts-per-unit-distance
in the stress output file (Soutput.xls). However, I think it is not doing
it correctly. I will look at it more and get it fixed. It can easily do
it, but I just have to be sure it is correctly programmed (this time
;-))... Stay tuned!
BTW Bart, Be sure to get the latest version of E-Tesla5.2x ("yesterday's"
version ;-)). It now runs 2.5 times faster thanks to Finn's brother
finding the problem with using floating point variables where they were not
needed!!
http://users.better-dot-org/tfritz/site/programs/E-TESLA5.ZIP
By far the greatest advantage of having this program in simple BASIC is
that so many people can easily look it over and make all kinds of great
suggestions!! This has really help the program tremendously!!
Cheers,
Terry
>At 07:10 PM 5/25/00 -0500, you wrote:
>Jeff & Marco,
>
>I just measured this, and it is definately large enough to be significant.
>However, as Marco pointed out, if the toroids out of reach, then it's out of
>reach (definately stick with the primary).
>
>Here were the results of my test. The winding dimensions are 12.5" x 44.5",
>18awg,
>CS=21.6pF, Ls=87.6mH.
>
>Ctop = 34" x 7.4" and calcs to 36.9pF (70.3kHz)
>
>Test #1:
>Toroid at top plane of secondary. Measured 86.2kHz.
>Ctop then calcs to 17.2pF (53% error from original calc).
>
>
>Test #2:
>Toroid raised 22" up. Measured 75.7kHz.
>Ctop then calcs to 28.2pF (23.5% error from original calc).
>
>This test also held true for a 16" sphere. Of course, capacity's were
>different but the results were the same (11pF gain in Ctop is significant).
>Jeff, did you model this with E-Tesla5? I took E-Tesla5 to work today to run
>on a faster pc and ran the setup mentioned above (true measured values were
>input into the program). The program showed 76kHz for Test #1 (but this is
>not what I measured). I need to rerun E-Tesla5 for Test #2 as I put in the
>wrong toroid height. I have a feeling it is going to be near 73kHz. I'll
>post this result tomorrow.
>
>Take care,
>Bart
>
>Tesla List wrote:
>Original Poster: "Jeff W. Parisse" <jparisse-at-teslacoil-dot-com>
>
>Barton & Marco,
>
>> Marco, you may want to consider making the toroid movable up and down.
>Malcolm
>> posted in a reply this week about fine tuning the resonator simply by
>raising
>> or lowering the toroid. Makes a lot of sense to me.
>
>I modeled this with E-Tesla 5.1 and tested with real parts. The amount of
>Fsec
>shift due to different toroid heights is too small to be significant on a
>big coil
>(like the Model 9J).
>
>Jeff
>
References: