Re: Bipolar primary design

["Tesla list" <tesla@xxxxxxxxxx>]

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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