[TCML] bipolar coil
bartb at classictesla.com
Sat May 3 18:23:59 MDT 2008
Better! Funny you mentioned Ed Sonderman's spreadsheet. Javatc started
as a spreadsheet adapted from Ed's spreadsheet many years ago. But, Ed's
spreadsheet can't account for high frequency changes in L or C, the
toroid size and position affects, lead length inductance, etc... but it
still gets you in the ballpark regardless. For those functions, you have
to be able to run integrals and that's when programming is a better way
to go. I could have used VB I guess, but I chose scripting since it
could be put on the web and then didn't require the Excel program to be
free for all regardless of the users location on the planet. Simply put,
Regarding the twins, the coils would actually resonate at 408kHz and
using a .035uF cap as you show, the primaries would end up at 1.4 turns
each and largely because the lead length inductance is very significant
on these twins due to their small size. This is why I was stating to use
a cap size even smaller. Probably the smaller the better (from a tuning
standpoint) as long as it remains outside of nst resonance.
I wonder if Ed is still coiling? He's probably still working at the golf
course I guess. Ed was very helpful to me when I started coiling. I
really enjoyed my correspondence with him. One of the nicest coiling men
I've had the pleasure of talking with.
David Dean wrote:
> Hi Bart
> Yes I screwed up calculating the resonant cap size.
> I failed to use parentheses in the calculator. Got 25.1nF.
> Let me try once more. Just rough and dirty, of course.
> 9000V / .060A = 150000 Ohms inductive reactance.
> 1/(150000*377) = 18nF resonant cap size. Better.
> Double that gives 36nF.
> Using 3 strings of 13 CD 942 150nF caps to get close
> Secondary 2.375" dia. X 11.85" winding length @ 84.8 tpi
> gives 5.0 H/D, 10.4mH, 4.8pF by Ed Sondermans spread sheet.
> Toroid 3" X 12" 13.3pF and resonant frequency 367kHz.
> Primaries need total of 5.5microH to resonate @ 363kHz.
> Primary ID 4.88", tube diameter 0.125", 0.25" spacing needs
> 7 turns for 11.7microH each. Again from Ed Sondermans spread sheet.
> A little better.
> On Saturday 03 May 2008 12:16:09 pm bartb wrote:
>> Hi Deano,
>> Not for a twin coil. Each coil will have 1/2 the total inductance. This
>> is what Kris is trying to account for. He's "doubling" the LTR cap size
>> to find 1/2 the inductance in the model. He will actually only use 1/2
>> the cap size as what he would insert into the model. Thus, if he used
>> 46nF, he would have to insert 92nF which will allow the model to tune to
>> 1/2 the inductance, in which case, he would require less than 1 turn per
>> coil. This is the problem he ran into. He has to lower the cap value to
>> change the LC ratio for more L.
>> Take care,
>> David Dean wrote:
>>> On Saturday 03 May 2008 05:27:41 am Kris Grillo wrote:
>>>> I think I'll just stick with the original plan of 60mA.
>>> Primaries in parallel and 46nF tank cap should tune
>>> (each primary) near 6 turns and be 1.84 times resonant
>>> cap size for a 9x60 NST. Frequency about 367kHz.
>>> No accounting for extra inductance in tank wiring though,
>>> that might just be the killer.
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>>> Tesla at www.pupman.com
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