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Output Voltage vs. Firing Rate (fwd)





---------- Forwarded message ----------
Date: Wed, 5 Aug 1998 14:05:23 EDT
From: Rscopper-at-aol-dot-com
To: tesla-at-pupman-dot-com
Subject: Output Voltage vs. Firing Rate

Terry,

I have been doing some experiments along the same line with my 8X6 system RSG
(scope traces will be avail. soon on http://members.aol-dot-com/rscopper/index.htm
- as soon as I get the GPIB card working again after installing WIN98).

I am using a Tek P6015 high voltage probe to look at different spark gap
configurations and have found the following to be true:

1) A series spark gap fires mainly at 120Hz.
2) Secondary firings within this 120Hz can occur if the primary resonates with
the driver transformer.
3) My sync 1800rpm RSG set at 120Hz operates erraticly at best with most of
the firing at the positive peaks.
4) My sync 1800rpm RSC set at 480HZ operates much more consistantly with
better sparks.

I conclude that you can get several sparks during the peak voltage time and
get better sparks this way.  Setting the gaps such that they fire at slightly
less voltage than if they were series gaps is required however.

I would think that the maximum fire rate would be the 1st notch quenching
ringdown time or maximum primary capacitor charge time.

My small tabletop coil with a series gap fires at 6KHz within the 120Hz with
secondary frequency of 850KHz.

P.S. If you think you want to install WIN98...DON'T DO IT. I had problems with
CD, GPIB, Sound, Colors, and just about everything else.

Scott
 
>Terry Wrote:

>Hi All,
>	We were having a little Colorado Tesla meeting on Sunday.  I noticed that
>my gap seemed to give better sparks when the gap was set to a lower voltage
>than maximum.  In other words, The streamers were longer with lower gap
>voltage settings.  Modeling shows that this is probably due to the fact that
>the firing rate probably increased by a factor of three from 120 Hz to 360
Hz.
>	I have always tried to design coils to create a very high output voltage.
>However, Sunday's experiments would suggest that we need a higher firing
>rate ( >120 Hz ) also.  In fact, one may need to sacrifice substantial
>output voltage to increase the firing rate to get the best streamers.  My
>latest gap design will be able to explore this realm in far greater detail.
>I suspect that once the output voltage is high enough to cause breakout, we
>need to use firing rate the push the streamers out rather than pure voltage.
>High voltages tend to cause many short streamers while high firing rates at
>lower voltage tend to create a single but much longer streamer.  Obviously,
>this subject is very important to our endeavors.  
>	My next gap design will allow easily adjustable voltage, high power, and
>very good quenching that should allow for very optimal adjustments of these
>parameters that seem important.  If anyone has any input to such issues
>please let me know.  
>	I was very impressed with Dave Burman's vacuum gap.  I never have used much
>airflow before but there seems to be a substantial advantage to having a lot
>of high-speed air flowing through the gaps.   Not only does air improve
>quenching but it also aids cooling.  With a little larger pipe and much more
>airflow, my present gap design can be greatly improved.  Hopefully, a static
>gap could handle very high power levels and still give excellent quenching.
>I suspect that the firing voltage can be carefully adjusted to give the best
>output potential and firing rate in order to produce the longest streamers.
>There is probably a "sweet spot" between these two factors.

>	Terry Fritz