Re: 8 kHz Tesla Coil

["Tesla list" <tesla@xxxxxxxxxx>]

Original poster: boris petkovic <petkovic7@xxxxxxxxx>

Hi Bart,
-----
> Multilayer will have breakdown limitations which I
> know you've
> already considered. Did you have some thoughts about
> this as far as a
> specific winding technique? It will still have the
> same RF loss
> issues, regardless.
>
> I think it was Antonio who mentioned a stack of flat
> coils. This
> would be interesting to look at. The distance
> between each flat coil
> would need to be separated enough to prevent coil to
> coil breakdown.
> Winding direction, id to od connection, all would be
> important to
> keep the stacks as compressed as possible to take
> advantage of the
> proximity (that would be the hard part).
-----
I've played a little at my workstation and considered
model of 1500-2000 meters of d=0.7 mm copper wire and
came up with a seemingly promising design.
For instance,with ~ 30 cm x 100 cm helicoidal
structure dimensions (12"x40") and 9 layers of the
wire constituting winding depth 2cm (~ 1"),the losses
at 9 kHz are not all that bad as concerns the
magnetical part.This takes into account practically
everything associating H-field ,longitudal skin and
proximity effects.Can be verified by taking advantage
of the usage of commercially available softwares (like
those of Vector Fields company).
In the same time ,the multilayer helicoidal structure
can provide us with several Henry of inductance while
still being suitable for high tension operation,and
withstanding enough of voltage stress among its
turns,if wound appropriately.

The price must be paid by virtue of the other side of
the coin though.A two-fold negative aspect of E-field
impact:
Firstly,as mentioned,the winding has increased
internal capacitance and more E-field energy stays
trapped among turns.
Secondly,the dieletric losses in the wall of the coil
(over the winding depth) are higher thicker the
wall.And these might be substantial .Moreover hard to
model ,predict,or even guess in right ballpark ( some
cases of a classical single layer coils reflect the
form material issue too ,if you remember Terry's
experiment with sonotube forms coils' low Qs).


Therefore ,there's much to ponder over multilayer
secondary designs let alone  winding techniques.

-----
<SNIP>
>
> It's hard to beat simplicity (single layer helical).
>
> Take care,
> Bart
-----
Fine concluding remarks.
I absolutely agree.IMO,getting down resonant
frequencies below 10 kHz for relatively small air core
coils and taking care of efficiency issues is simply
not worthy of efforts.Don't see points in doing it.

All the best,

Boris