More results from DRSSTC land

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Original poster: Steve Conner <steve@xxxxxxxxxxxx>

Hi all,

I have had my DRSSTC together and working for a while now, and have made 
some interesting observations.

1) By hooking it to a digital scope I was able to measure the instantaneous 
power output from the H-bridge, and integrate it to get the bang energy.
http://www.scopeboy.com/tesla/drsstc/scope/analysis.gif

It works out to over 5 Joules. Remember this system has a 4x13" toroid and 
5.5x13" secondary coil, therefore it can hold maybe 1 to 1.5J before 
breakout. So this is evidence for the argument I was having with Antonio a 
while back ;)

This actual bang produced a 22" ground strike. It was operating on the 
upper pole at ~220kHz. There are some more detailed screen dumps where you 
can see exactly what the PLL driver is up to-

http://www.scopeboy.com/tesla/drsstc/scope/bangcapture36.jpg
http://www.scopeboy.com/tesla/drsstc/scope/bangcapture36_zoomstart.jpg
http://www.scopeboy.com/tesla/drsstc/scope/bangcapture36_zoom_iddle.jpg
http://www.scopeboy.com/tesla/drsstc/scope/bangcapture36_zoom2.jpg

It was not too good at tracking the sudden shift in frequency due to the 
arc connecting with ground. I later found out that the tuning was set 
wrongly and it was hitting the lower frequency limit. It probably tracks 
better now, but I never got the chance to retest it.

The coil was demonstrated at Derby and managed a 33" arc to ground. I have 
some pictures that were taken by Adam Horden http://www.adamhorden.net/

http://photos.adamhorden.net/SCDRSSTC/DSCF3069
here is the actual 33" arc (partly blotted out by sunlight reflecting off 
the topload of another coil)

http://photos.adamhorden.net/albums/Derby_2005/SC_DRSSTC.wmv
a movie of the coil operating (wmv format, might not play on macs or linux?)

I was surprised that it "only" got 33". I tried several different tunings 
but the upper pole/tight coupling setup gave the best result of all. With 
this tuning it needed only ~180A peak to get that spark length, and 
flashover was what limited it. I tried currents up to 300A with the other 
tunings but couldn't beat that length.

No matter the tuning, the burst length didn't cause any more growth (only 
brightening and thickening) above ~150us and the streamers had reached more 
or less full length by a breakrate of 100Hz. I have some ideas about that 
lack of growth and will post them later.

Steve Conner