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Re: Tesla calculator frustration.
Original poster: "Terry Fritz" <twftesla-at-qwest-dot-net>
Hi Bill,
It is not really simple. You need a couple of programs and a fair bit of
knowledge. Let me "try" :-)
First I like to figure out the secondary inductance. I just use the L(uH)
= (N x R)^2 / (9R + 10H) formula from Matt's site but many programs do it too:
http://home.earthlink-dot-net/~electronxlc/formulas.html#helic
I get 35.85mH for your secondary coil's inductance.
Then you need to know the resonant frequency of your system with E-Tesla6.
I typed the following into E-Tesla6. I had to guess at a few numbers.
Your 4 inch spaced pizza pans will not matter really but you should use the
center of them for the terminal height in E-Telsa6.
--------------------------------------------------
E-TESLA V6.11C November 21, 2000
Grid Size = 200.000000
Scale Multiplier = 1.000000
Terminated Coil
Ceiling Distance = 100.000000
Wall Distance = 50.000000
Primary Height (Inner Turn) = 12.000000
Primary Inner Diameter = 9.750000
Primary Outer Diameter = 24.000000
Primary Height (Outer Turn) = 12.000000
Strike Rail Height = 0.000000
Strike Rail Diameter = 0.000000
Secondary Base Height = 12.000000
Secondary Diameter = 6.625000
Secondary Length = 27.625000
Secondary Inductance (mH) = 35.850000
Terminal-1 Height (center) = 45.000000
Terminal-1 Cord Diameter = 8.000000
Terminal-1 C-C Diameter (toroid only)= 23.500000
Terminal-2 Height (center) = 45.000000
Terminal-2 Cord Diameter = 0.000000
Terminal-2 C-C Diameter (toroid only)= 0.000000
Top Voltage = 100.000000
Pass Ccalc (pF) Change Fcalc (Hz)
1000 C=18.37255 Err%=1837154.625000 F=196105.98
2000 C=30.79789 Err%=67.629959 F=151465.97
snip...
27000 C=43.10861 Err%=0.000491 F=128024.63
28000 C=43.10872 Err%=0.000266 F=128024.46
29000 C=43.10874 Err%=0.000024 F=128024.45
--------------------------------------------------------------
Ok so we get 128.0kHz as the secondary system frequency.
No you can select from all kinds of programs. I'll us my silly one since
it is "mine" and "I" like it ;-)) But there are far far better ones...
Mine needs the dos screen font and all set up which is a pain... (read the
directions if you try it)
http://hot-streamer-dot-com/TeslaCoils/Programs/teslapro.zip
Note this picture of the program's output:
http://hot-streamer-dot-com/temp/BillV.jpg
Now you need to separate the total secondary capacitance (43.10874pF) from
the Medhurst (secondary self capacitance) capacitance (12.23328 from my
program). You just subtract:
43.10874 - 12.23328 = 30.875pF which is the effective "top load"
capacitance. Note that the secondary frequency (in my program) is now
128.0 :-))) Of course, "my" programs always work out :-)))
The green number by the primary turns is the tap point of 7.34 turns which
is the answer you seek and assuming I used the right numbers and did not goof.
A check is that the secondary and primary frequencies match. Of course,
you may have to adjust the tap point a little for streamer loading and room
effects but it will be really close.
E-Tesla6 kind of threw a monkey wrench into many programs in that it
suddenly provided a way to find the resonant frequency, and top load
capacitance. Most existing programs were not ready for this and they have
not caught up yet, so it is still a bit messy... If you want one of the
most advanced programs, check out Kurt's:
http://hot-streamer-dot-com/temp/TCplan.zip
(needs Excel to run)
I am sure the programs will catch up pretty quick once we stop changing the
rules all the time ;-))
Hope this helps.
Cheers,
Terry
At 05:38 PM 5/30/2001 -0400, you wrote:
>This really should be quite simple, but no...
>
>I just want to calculate where I *should* tap my primary, given the
>following:
>Cap: 0.06uF
>Primary: Inner diameter = 9.75", 1/2" spacing (center to center), 1/4"
>tubing
>Secondary: 1000 turns, 27.625" winding length, 6.625" diameter.
>Topload: 8" chord, 23.5" center to center (capacitance = 34.845?)
>
>
>Previously (with a smaller topload), I managed (or so I thought) to do
>the calculation using JHCTES version 3.2, at
>http://www.miramarcollege-dot-net/faculty/jcouture/tesla/
>
>but now I can't see how I ever did it. The weird thing here is that
>what I would logically like to specify as input parameters, like primary
>interturn spacing, are output parameters. I have to try to adjust the
>input parameters to get output parameters that match my existing
>primary.
>
>I've also tried E-Tesla 5 and 6 - got significantly different results,
>and don't quite see how to calculate my tap point anyway.
>
>Are the specs I've listed sufficient for calculating the tap point?
>
>
>Another question, about toroid topload shape: I made mine from 8" dryer
>duct and two 16" pizza pans, but the pizza pans are about 4" apart.
>Should that be a problem? Any idea how much that affects the toploads
>capacitance?
>
> Thanks again,
> Bill V.
>