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Re: NSTs and Cap charging tests (Static gap-Sync vs. Chaotic BPS)
to: Tony
Sounds like you put the caps to good use. Also sounds like you have a nice
performing coil setup. I would suggest going to a rotary synchro sparkgap
to eliminate your oxide problem and achieve max performance from your coil.
Regards,
Dr.Resonance-at-next-wave-dot-net
-----Original Message-----
From: Tesla List <tesla-at-pupman-dot-com>
To: tesla-at-pupman-dot-com <tesla-at-pupman-dot-com>
Date: Monday, April 19, 1999 4:08 AM
Subject: Re: NSTs and Cap charging tests (Static gap-Sync vs. Chaotic BPS)
>Original Poster: TeslaTec-at-webtv-dot-net (Tony R Greer)
>
>Hi John, Richie, Malcome, Gary, Terry, Reinhard, Dr. R., and all others
>following this thread.....Although I'm a rank amature at TCs compared to
>you guys, I thought I would share the results from some testing I've
>done over the last three days on 'Reddy Kilovolt' , my 8" x 34" coil
>with 15,000 volt/150 mA NSTs, 26.77 nF tank cap. , and a Gary Lau style
>single static gap with vacuum airflow quenching/cooling. The NSTs and
>caps were selected to resonate at 60 Hz, or thereabouts. During these
>tests, only the gap spacing and input voltage were changed; everything
>else remained as above.....As stated in my last post, with a gap spacing
>of about .375", when input voltage reaches about 100 Volts, the input
>current drops sharply, from 30-35 Amps to 16-18 Amps, and the sound of
>the gap and sparks changed from a raspy noise to a steady, pleasing
>tone. Spark output also decreased slightly. This sounded to me like the
>gap was firing in sync with the line, so I tried the following to
>confirm this. (If anyone sees a flaw in these tests, please say so, as
>I'm here to learn). First, I set up the O-scope (single trace) about 20
>feet from the coil, and attached a short length of wire to the probe. I
>then adjusted the vertical amp and horizontal sweep rate (in the 'free
>run' mode) to display two complete sine waves from the 60 Hz background
>'hum'. When the coil was fired, the initial bang from each discharge
>would show up superimposed on the 60 Hz sine waves as a vertical spike,
>followed by the ringdown envelope. Sure enough, when the NSTs were
>drawing the least current, and the noise of the gap and sparks became a
>steady tone, the gap was firing in perfect syncronization with each 1/2
>cycle of the line. Each bang occured at EXACTLY the same place on the 60
>Hz waveform, just a few degrees before each voltage peak. I was amazed
>to see the gap firing with such regularity, as there was absolutly no
>jitter at the firing point on each 1/2 cycle. ('Scope triggering turned
>off and set to 'free run'). Note: gap is two 1-1/4" copper endcaps with
>3/8" holes in the center for vacuum airflow. Gaps were cleaned before
>tests were done. After running the coil for a few minutes, oxide starts
>to appear, and firing starts to become erratic in the sync (120 BPS)
>mode. Finaly, when enough oxide builds up, this sync mode completly
>stops, and chaotic firing prevails , although this dosen't seem to
>decrease spark length untill oxide gets heavy enough to cause the safety
>gaps to fire. If input voltage is either raised or lowered, chaotic
>firing starts, current draw about doubles, and spark length increases
>slightly. Raising the input voltage past 100 Volts to 120~140 Volts ,
>sparks grow rapidly in length, up to 6 foot, although input current
>rises to 35-40 Amps. As one would expect, decreasing the gap spacing
>lowers the voltage where the 120 BPS line sync occurs to about 60 Volts
>input. At this spacing at 120 Volts, the gap was firing twice during
>each half cycle (240 BPS) once just before and once just after the
>voltage peak, although spark output was WAY down to <1 foot, even with a
>breakout placed on the toroid. Widening the gap increases the spark
>length up to the point where the cap can no longer charge and fire the
>gap at least once per half cycle (about 7/16"). Best performance for
>this coil is about 3/8" or .375"~400" gap
>spacing...................................... Conclusions???
>(Semi-uneducated guesses, really) Single static gaps can fire at
>precisely every half cycle and within a few degrees before the voltage
>peak, at least for my 60 Hz resonate NSTs / Cap combo.....With proper
>gap spacing and charging current, the gap can fire multiple times per
>half cycle.....When not firing at 120 BPS or some multiple, firing
>becomes chaotic.....Chaotic firing=higher current draw=lower power
>factor=lower efficency, but=longer sparks.....Sync firing=lower current
>draw=closer to unity (higher power factor)=higher effiency, but=shorter
>sparks.....Oxide on copper gaps greatly affects the firing voltage and
>sync stability.....Best efficency (highest power factor) occurs at 120
>BPS.................Like I said, these are only observations and
>guesses; All coments welcome, as well as corrections! SAFE
>SPARKIN'...T-coiler Howdys from Texas........... Tony Greer
>
>
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