New DRSSTC Benchmark

["Tesla list" <tesla@xxxxxxxxxx>]

Original poster: Steve Ward <steve.ward@xxxxxxxxx>

Hi everyone,

Last night i pulled out my large DRSSTC:

<http://www.stevehv.4hv.org/DRSSTC2.htm>http://www.stevehv.4hv.org/DRSSTC2.htm

(there are no updates from last night, though).

I increased my tank capacitor to 569nF (measured) using 15 parallel 
strings of 4 caps in series (our favorite CDE 942C's).  The results 
were just awesome with this larger capacitor (previously the tank cap 
was 360nF).  My longest spark was 12 feet to an intentional target 
(so this mark was hit several times to be sure!).  Soon after 
achieving 12 feet, the breaker pops.  I am still running on a 20A 
breaker (240V line).  My power factor was probably around .65 or so 
(still using a voltage doubler at the moment for the 700VDC).  So 
given the amount of time in which the breaker tripped (about 1 minute 
or so), that should put me at roughly 9600VA or about 
6240W.  Hopefully i will later verify this ~6300W figure later with 
my active PFC supply (which makes it easy to read the DC V and 
I).  If the power input was in fact 6240W, than my "Freau number" 
would be about 1.822... not amazingly more efficient than a spark gap 
coil, but im not complaining :-).

Some various operating parameters:

Primary Fo: tuned to about 37khz (just a bit lower than resonance).

ON time: about 190uS or 7 RF cycles (for 12').

Peak inverter current: 1200A for streamers, 1400A for ground arcs.

When operating with the grounded target at a mere 116" straight line 
distance, i was hitting the target perhaps as often as twice a 
second, whereas before 116" would perhaps occur every few 
seconds.  So the increase in performance is apparent, and im VERY 
happy with it!

How much more spark can this coil generate?  I'd say not much.  At 
one point there was a surface flashover from the very top of the 
secondary to the bottom, and actually shorting out 2 primary turns 
with a loud BANG! inverter survives!  I believe trying to push much 
further may destroy the secondary winding (being made from 
sonotube).  But again, i cant ask for too much more as the sparks are 
currently ~3.2X the winding length.

Steve Ward