Re: glass instead of pvc

["Tesla list" <tesla@xxxxxxxxxx>]

Original poster: "Dr. John W. Gudenas" <comsciprof@xxxxxxxxxxxxx>

Hi Sean

On Jul 3, 2005, at 11:06 PM, Tesla list wrote:

> Original poster: sean <sean@xxxxxxxxx>
>
> Hi, I had arcovers from the feedback coil to the secondary on my
> vttc to
> the point where I had to take it apart and put it in a box.  Info here
> http://www.firethroat.com/v.php
Experimenting with my dual 833A VTTC the only time the grid coil
would get corona or arc was when the coil
was not properly tuned. Tuning is critical for good VTTC performance.
Tuning can include adjusting almost any component
including tank capacitance, grid leak resistor, primary and grid coil
turns etc.

Good coil geometry is important too. Much like with a disruptive coil
the secondary needs to be placed at the proper height
relative to the primary as well as having everything aligned. This is
"usually"  where solenoidal primary windings are even
with the secondary,  but other geometries are possible too.  Your
coil is working so I suspect that you are close.
VTTC coils are usually close coupled, but with close coupling proper
tuning is imperative to prevent arc-overs. You don't
need to put it in oil.

> Even when it was not arcing over, the pvc it was wrapped over caught
> fire which would not be put out and sucks a considerable amount of
> power
> away from the secondary.  I have had problems with pvc burning in
> sgtcs
> as well.  Would it be possible to use tubular glass instead?  any
> other
> possible suggestions here?  I think pvc is ok, but if it can burn, it
> becomes problematic.  What can I use?  I know everyone always
> laughs at
> this.. but what about putting the whole coil under oil and let the
> toroid actually float in 2 senses?  Then I could get a much better
> coupling without fear of arc-over.

PVC works well. At your power levels you should not generate enough
heat to melt the primary form
unless the coil is not properly tuned. Arc overs indicate a tuning
problem. Again at your power levels it
is not necessary to put the coil in oil.

Do not use glass as a primary coil form.  There are many reasons for
this including safety.
My preference is canvass phenolic but with your coil PVC should work
fine.

Contact me off list if you want to discuss this further, I can also
send some coil pictures.


John W. Gudenas, Ph.D.
Professor of Computer Science
> any ideas?
>
> --
> sean <sean@xxxxxxxxx>