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Re: Safety Gap/Resonant Rise/Chokes
From: Thomas McGahee[SMTP:tom_mcgahee-at-sigmais-dot-com]
Sent: Thursday, November 20, 1997 4:31 PM
To: Tesla List
Cc: V.C.Watts-at-btinternet-dot-com
Subject: Safety Gap/Resonant Rise/Chokes
>
> From: Vivian [SMTP:V.C.Watts-at-btinternet-dot-com]
> Sent: Thursday, November 13, 1997 1:05 PM
> To: Tesla List
> Subject: Safety Gap
>
> Hi All,
> Having read various comments in the list I feel I should have a
> safety gap to protect my neon especially as I want to open up my spark gap.
> I currently have two 3mH inductors one in each leg of the neon transformers
> secondary. The connections goes transformer, inductor, capacitor, primary
> coil, inductor, transformer. The spark gap is across the two inductors
> which closes the capacitor - coil circuit. Their is clearly no point
> putting another gap across the spark gap so the logical place would be
> directly across the neon. However I cannot see how this helps, as any
> energy to get into the neon has to come through the inductors which already
> have the gap between them, limiting the potential.
>
> Can anyone explain.
>
> Viv Watts UK.
Vivian,
The transformer and capacitor can form ANOTHER resonant circuit in your
Tesla Coil. I have measured rises up to 50KV from a 12KV neon. These voltages
can kill the neon very quickly.
The safety spark gap at the neon is actually TWO safety gaps, each connected
between the center tap ground (case) and one leg of the HV side of
the transformer.
Just this past week one person posted a note on bottle caps and how they
found that when they had a certain amount of capacitance on their neon, it
experienced sparks that snaked the entire length of the porcelain
insulators. THAT is resonant rise! I use resonant rise on my H&R trannies
to get the voltage up to 10KV from about 5KV. Resonant rise is very real
and can be very useful, but also very dangerous to your neons. The
safety gaps are the only sure way to protect them from this particular
problem.
I know that you think that because you have a big spark gap on one side of
the chokes that that should also protect your transformer. 'Taint
necessarily so. When the main spark gap fires the chokes can ring up
quite a bit, and the HV they produce in the form of nasty spikes is
delivered in this case directly to the poor transformer. Don't go looking
for hash on the far side of the chokes as the culprit here. The very
chokes that are there to protect the transformer can actually act up in
such a way as to sometimes produce some pretty nasty sparks of their
own. That is why you want to do anything in your power to squash the Q
of the chokes. As an experiment I had a choke that consisted of
a bunch of turns around a 2" PVC pipe connected "hanging" off the main
spark gap. In other words, just ONE wire connected, and that to the
main spark gap. I could get that coil to produce clearly visible corona
from its free end.
There are some truly strange things that occur within the Tesla coil
circuitry. Sometimes our protection circuits can actually help bring
our trannies down if we are not careful.
Bottom line: Do not leave out the safety gaps!!! There is more going
on in your circuit than you think!
Hope this helps.
Fr. Tom McGahee