Re: toroid capacitace(bi-polar coil)

["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 8/12/02 6:53:58 PM Pacific Daylight Time, tesla-at-pupman-dot-com
writes:


>
> Hello all,
>
>     This is Nolan I have been working on a new bi-polar tesla coil.  I use
> Ed Sonermans tesla coil spread sheet to calculate where to tune the primary
> coil.  I read before to tune a bipolar telsa coil to cut the inductance of
> the secondary coil in 1/2 to maintain tune with the same tank capacitor and
> that will give you the correct place to tap the primary coil. Would the
> capacitance change since there will be one on each coil or will it still be
> the same, I need to know what parameters to put in the spread sheet to
> figure where to tap the primary coil. Ok I have 2 new toroids each measures
> 21" outer diameter and 4.5" in the cross section for total capacitance of
> 22.75pf.  When the tesla coil is set up will the toroids be in series
> together cutting the capacitance in half to 11.375pf?  Or Will the toroids
> be in parallel doubling the capacitance to 25.5pf?  Or will it stay the
> same? Do you have any other tips on using Ed Sonderman telsa coil spread
> sheet to calculate for a bi-polar telsa coil. Thanks a bunch help is greatly
> appreciated!
>
> Sincerely,
> Nolan Moore



Nolan,

If you are building a coil that is mounted horizontaly, with a toroid on each
end and the primary in the center, then we have one primary coil and one
primary capacitor - correct?  You would enter the dimensions for one half of
the secondary along with the capacitance for just one toroid.  The spreadsheet
is easy to find different component values once you get used to it.  I input
the secondary coil and toroid capacitance info.  Then the primary information
(using all turns of the primary i.e. 14 for a 14 turn primary), and check what
the required primary capacitance would be.  It might come out to .0169 ufd for
instance.  You know that you need a capacitor at least this large, with the
primary tapped out at the last turn, allowing no room for tuning.  Then you go
back to the primary input information and change it to say a 10 turn primary. 
Now it will show that a larger capacitor is required, say .0192 ufd.  So you
would select ! a capacitor that falls in that range.

Ed Sonderman