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Re: overquenched spark gap?

Original poster: "Chuck Hobson" <g0mdk@xxxxxxxxxxxxx>

Hi David,

I've always wondered about using asynch rotory spark gaps. Misfires occur when it the rotor gap moves in and out of sync with the ac voltage. With a syncronous spark gap properly set and appropriate firing occurs, nearly all the energy derived from the ac power input is used up in the form of sparks, noise, light, etc. As such the ac power factor would be very near unity. During misfires the primary capacitor behaves as reactively and returns the energy back to the ac source. Thus, the ac power factor becomes less than unity. Thus, the VA would be accordingly larger than the true input power. I would think you can still get massively long sparks during a proper firing and no sparks during improper firing. The bottom line is that you are probably getting a jittering power factor: unity to nearly zero. What your safety gap is doing is problematic. I would think that spark gaps such as you mentioned would glow red at least with the power you are using if they were the only items contributing to inefficiency. I hope this is helpful.

Chuck

----- Original Message ----- From: "Tesla list" <tesla@xxxxxxxxxx>
To: <tesla@xxxxxxxxxx>
Sent: Friday, September 30, 2005 8:35 PM
Subject: overquenched spark gap?


Original poster: DRIEBEN@xxxxxxxxxxxxxxx
Hi all,

Here recently I got some good sparks and spark image
photos of my Green Monster (GM) Tesla coils system.
I have a few more even better spark shots that I
haven't loaded to the webpage yet but hopefully can
within the upcoming week. I was wondering though if I
could be possibly overquenching the spark gap. The
reason for this question is that I am getting 11 ft
power arcs now from GM and that certainly looks im-
pressive, but I am also drawing about 60 amps at
250 to 270 volts from my control panel to get this
output and that seems a bit inefficient to me. Of
course I've almost exclusively kept my runtimes to
< 15 seconds since I'm firing it on my driveway in
plain view of the entire suburban cove on which I
reside. My spark gap system is a standard asynch
rotory seriesed with a 4-electrode, 3-gap RQ type
air-cooled stationary gap. The 4 "electrodes" are
each a 2" dia x 5" long piece of copper pipe and they
are spaced appr 1/16" to 1/8" apart. The main rotory
gap can be pretty plainly seen on my webpage at:

dawntreader.net/hvgroup/david/gm

I think there is also an image of the RQ stationary gap
but it's not as easy to see. Originally, I only had the
main asynch rotory gap but found that the SG electrode
components were getting VERY hot with just 20 to 30 sec-
onds of run time. This was also before I finished fine
tuning the system and tightening the primary/secondary
coupling. I added the RQ seriesed gap to share the thermal
burden with the rotory gap. With the RQ gap in place,
I was originally getting 7 ft to 8 ft sparks before
adjusting the coupling but once the coupling was tightened
up, the output increased to the 10 ft to 12 ft range.
However, I was hoping to be able to get sparks in the 14
ft range with the available power that I have and I know
that the SG is the most critical point of a standard SG
driven Tesla system for losses. I'm thinking of bypassing
the RQ stationary gap next time I fire it off and while
monitoring the rotory SG electrodes for excessive heating, to
see if the output increases even more. I am also thinking
that when the pri/sec coupling was too loose,then more of
the osciallations were remaining and recirculating in the
primary circuit components and thus the excessive SG elec-
trode heating. I also noticed my "hause" .1 uFd, 50 kV pulse
cap getting noticable external warmth when firing it with
the "loose" coupling but that seems to have improved with
the tightened coupling.


All of the pertinent specs are on the webpage and any
suggestions would be greatly appreciated ;^)


David Rieben