Re: toroid capacitace(bi-polar coil) design

["Tesla list" <tesla-at-pupman-dot-com>]

Original poster: "by way of Terry Fritz <twftesla-at-qwest-dot-net>" <Esondrmn-at-aol-dot-com>

In a message dated 8/13/02 10:49:42 PM Pacific Daylight Time, tesla-at-pupman-dot-com
writes:


>
> Hi Ed and howdy to all,
>
>     This is Nolan, I will elaborate on my tesla coil design more.  There are
> 2 separate secondary coils. they are 3.5" in diameter and wound 17.25" with
> awg28 enamel wire.  There are 2 separate primary coils wound with 6awg solid
> ground wire inner diameter measures 5.825" and is spaced .25" between turns
> for a total of 6.75 turns max.   The wire is mounted in plexi-glass
> supports.  What I would like to do is REMOVE the inner 2 turns to give more
> clearance between the coils but I need to know if I will have enough turns
> to tune the coil.  I nave 2 new toroids they measure 21" in diameter and
> 4.5" in the cross section.  My tank cap are 2 rated 0.03uf at 35kv for a
> total of 0.06uf at 35kv, I could add one or 2 more for 0.09uf or 0.12uf, if
> need be.  But if its close with taping the primary coil ill make smaller
> toroids.  The coils will share the tank cap and same static spark gap. the
> power supply are three 7.5/60 franceformes wired in parallel they are feed
> through a variac and a line filter, I also constructed one of terry's nst
> protecion filters. Everything has been put in to the same box.  Is it
> dangerous to have the tank circuit that close to yourself????? But its not
> like its right net to each other.  Here are some pictures I just posted
>
> http://www.hot-streamer-dot-com/nolan/minicoil/revampintotwin/  
>
> So if I remove 2
> of the inner primary turns resulting in a inner diamiter of  7.75" and max
> turns of 4.75 I calculate that the primary coil will be taped between 3.9
> turn to 4.25 turn.  By the way I do use you tesla cal. allot I also have
> added al allot of stuff and modified some of it. I love it thanks for
> creating that tesla spread sheet! Thanks for your help!
>
> Sincerely,
> Nolan Moore
>



Nolan,

If I understand the terminology correctly, I would call your coil a twin system
as opposed to bi-polar.  You have two separate secondaries with primaries that
share a spark gap and primary cap.  I calculate the secondaries will resonate
at 188 khz with the 4.5 x 21" toroid.  Each primary (as is, without removing
any turns) will provide 13 uh of inductance.  Since these are additive, I now
adjusted the number of primary turns in the spreadsheet so the inductance would
be 26 uh.  The primary capacitance required is .0276 ufd.  If you use one .030
ufd cap, the coils should tune with each primary tapped at turn 6.4.  I would
not remove any turns from the existing primaries.  You have about 1.15"
clearance now which should be fine.  I would adjust the secondary height so the
bottom turn of the secondary is just even with the top of the primary -
providing the primaries are wound flat.  If they are inclined, you will need to
do som! e testing to find the best coupling without getting too much.

I believe these twin coils are normally operated out of phase from each other,
so one of the primaries should be wound opposite from the other - correct?

Good luck, Ed Sonderman