RE: Safety Gap Puzzle

["Tesla list" <tesla-at-pupman-dot-com>]

Original poster: "David Dean by way of Terry Fritz <twftesla-at-qwest-dot-net>" <deano-at-corridor-dot-net>

Hi Greg, list,

I have noticed some longer, thicker streamers when the safety gap fires on
my 4" coil, but never thought much of it as my safety gap is a single static
gap made from two "spoons" hammered out of some 20 mil copper sheet and
connected directly across the terminals of the SRSG.
When the safety gap fires, all the energy goes through the primary circuit,
so I would guess that a more powerful streamer would be considered normal. I
also guess that I have some inductive kick going on with the present ballast
configuration, as I have opened the safety gap to 3/4" in order to be able
to get up to 220VAC input to the ballast without firing the safety. I
usually run the coil with a breakout point on the toroid (actually more of a
quasi-toroid, 6 X 24 Styrofoam disk with the edges rounded over and covered
with aluminum tape) but with the breakout point removed and setting the
variac to just sub breakout will result in every isolated metal object in
the building getting a charge. In darkness it is possible to sometimes see
some discharges off of or between these objects. If any of the objects are
touched, a nasty shock will be received.

Several days ago, a friend came by to get a fuel tank from one of his
tractors welded up because it had developed a pinhole leak in the bottom and
was loosing diesel. After repairing the tank, he ask so see some lightening.
I fired up the coil, but could not get up to a normal power level without
firing the safety. This proved to be due to high humidity in combination
with a lot of dust (the state highway out front is under construction) and
the safety was being triggered by a discharge between the bottom of the
secondary and the inner turn of the primary coil. Being the stubborn fool
that I am, I opened the safety up to a full inch. I also wiped the secondary
coil down with a rag with some isopropyl alcohol to remove the dust and
moisture and try to fix the pri to sec flashover. That is when things got
interesting.

I still could not get over about 180V in to the ballast before the safety
would fire. At the firing of the safety, an arc of 18" length, white and
thick, came out of a large metal roller (about 300 pounds of iron) that is
on the top (wooden) shelf at the back of the shop. It terminated at a point
where a piece of romex is poked through the (metal) ceiling to feed an
outlet lower on the shelves. This occurred several times. Upon
investigation, I found that the arc had penetrated the outer sheath of the
romex and was finding the bare copper ground conductor in the cable. I
thought this was rather bizarre, and have thought about it some during the
long sleepless nights, but have not come up with a plausible explanation for
the strange discharge.

later

deano

> -----Original Message-----
> From: Tesla list [mailto:tesla-at-pupman-dot-com]
> Sent: Saturday, June 30, 2001 11:26 PM
> To: tesla-at-pupman-dot-com
> Subject: Safety Gap Puzzle
>
>
> Original poster: "Gregory Hunter by way of Terry Fritz
> <twftesla-at-qwest-dot-net>" <ghunter31014-at-yahoo-dot-com>
>
> Dear List,
>
> I shot a few minutes of video tape of my newly
> refurbished 4" x 24" 1080VA coil last night, and
> grabbed a bunch of the frames as JPG stills.  One of
> the stills revealed an interesting effect.  The shot
> happened to catch the NST supply in the background
> behind the Tesla coil with the safety gaps firing, and
> the toroid streamer is MUCH thicker & more intense.
> Marc Metlicka mentioned a similar observation to me
> some time back, but I needed to see it to appreciate
> how dramatic it is.  What is that about?  I have a
> safety gap going to ground from each HV bushing on the
> NSTs, so for an instant, the tank circuit is
> effectively shorted to ground, and it's increasing the
> streamer current!  Do I need to redesign my main spark
> gap with a grounded center electrode???
>
> I'll attach "sparkz10.jpg" should you wish to have a
> gander.
>
> http://hot-streamer-dot-com/temp/sparkz10.jpg
>
> Greg
> http://hot-streamer-dot-com/greg
>
>
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