Bi-Polar Design

["Tesla list" <tesla@xxxxxxxxxx>]

Original poster: "Ralph Zekelman" <gridleak@xxxxxxxxxxxxxx>

Hi Patrick and Dr. Nicholson,

I will be interested in hearing about the developing bi-polar. There are
several photos of my bi-polar coils at 
http://hot-streamer.com/temp/RalphsCoil/
The coils shown have all been capable of a spark equal to the length of the
secondary except for the giant 48-inch coil which had serious problems of
not being able to support the weight of the "rabbit ear" arms.

I experimented with various arrangements to bring the arms up at
a right angle to the long axis of the secondary. This is probably the
usual method. I also tried various mechanical arrangements to bring
the arms out some distance parallel to the long axis of the secondary before
curving them towards the center. I could never overcome the weight problem.

How are you planning to design the arms? Where will you mount
the 3 x 14 toroids?

Finally, I have what may be the winning entry in the stupid question contest:
As the voltage across the ends of the secondary must increase as the arm
spacing increases, is it ever possible to get a spark longer than the length
of the secondary? Is this just a matter of insulation design or will the spark
always arc the shorter distance directly across the secondary (probably
arcing to the nearest primary turn.)

Ralph




-----Original Message-----
From: Tesla list [mailto:tesla@xxxxxxxxxx]
Sent: Wednesday, May 24, 2006 11:31 AM
To: tesla@xxxxxxxxxx
Subject: Re: Bipolar primary design

Original poster: Paul Nicholson <paul@xxxxxxxxxxxxxxxxxxx>

Hi Patrick,

 > The secondary winding length is 3.25" x 32", wound with
 > #28 wire, capped with a 3" x 14" toroid on either end.

 > My understanding is that to analyse the properties of such a
 > bipolar coil, I just need to "cut it in half" and analyse it
 > as per a regular coil. In that case, I have a 3.25" x 16"
 > secondary with a single toroid.

Yes, that's it.   The plane through the center of the secondary
is (if everything is nicely balanced) at zero potential, so each
half of the secondary behaves as if it's a regular quarter wave
coil working against a groundplane.

Put your half-coil secondary dimensions into JavaTC to cross-
check that Fres prediction.  There'll be some error because the
coil is horizontal, and the actual Fres is likely to be a little
lower than these programs predict, so make some allowance for
that in the primary design.  If you want to get a feel for how
much allowance to make, put a wall distance into JavaTC equal to
the height of your secondary/toroid axis above ground.  That ought
to return a lower limit to the possible Fres.

 > one simple question....since I've cut everything "in half", does
 > that include this primary? Do I need to double my primary, ie,
 > use 24 turns for my REAL coil?

No, no need to halve or double anything here.   Calculate primary
Fres using the actual coil and cap that you plan to use.

The above is the 'stock' advice, but bipolar coils are not so well
studied or understood, so keep that in mind - and good luck!
--
Paul Nicholson
Manchester, UK.
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