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Re: NSTs and Cap Charging.
Malcome, John, Richie, Terry, and All,
Just thougt I'd report on some observations while making adjustments to
my 8" x 34", NST powered coil that might have some relation to this
thread. (Quick specs; 15,000 V / 150 mA NSTs. C=.0267 uF. Spark
gap=static single gap with vacuum airflow quenching (Gary Lau style) ,
Variac input control to NSTs. Transformer voltage and current were
chosen to to resonate at 60 Hz with Maxwell pulse caps on hand.........
After cleaning and adjusting the gap to about .36", I started to
increase the Variac setting, while watching the input Volt and Ammeter,
and the output mA meter. the gap started fireing at about 30 Volts
input, and at about 60 Volts or so, floating streamers start to break
out. At about 90 volts in, the Ammeter is reading erraticaly between 25
and 30 Amps, streamers are multiple and about 3' long, and the noise
from the gap and streamers is very ragged and more like 'white noise'
(many frequencies). But when 96 volts was reached, input current
SUDDENLY droped to about 16 Amps, and the output current droped from 200
mA to 100mA, and became very steady. Streamers shrunk slightly (maybe
10-15%), but most noticeable was the different sound of the gap and
streamers. At between 96 and 98 Volts, the noise became a steady buzz,
like a single note. Probably firing in sync with the line, because
raising the Voltage past 98 Volts would again cause the current to
double and the noise would regain it's raspy sound, and streamers
regained their original length. Past this point, no other 'notch' was
found, although streamers grow to almost 6' at 120Volts input at about
35 Amps. Also, widening the gap to .375" moved this 'notch' up to 100 to
102 Volts. Another thing of intrest is this 'notch' effect only happens
for a few minutes after removing the oxide from the sparkgap (large
copper endcaps w/ 3/8" holes in the center for airflow). After a few
more minutes, the safety gaps start to fire. A light sanding of the gap
restores original performance. I think a sync RSG would eliminate those
problems and improve performance. What do ya'll think? I really haven't
drawn many conclusions to these effects, but thought it might provide
some additional information for this thread. Any comments, suggestions,
or questions would be greatly
appreciated.............................................
T-coiler Howdys from Texas !
Tony Greer