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