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Re: glass instead of pvc



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>