New primary test
From: Barton B. Anderson [SMTP:mopar-at-uswest-dot-net]
Sent: Saturday, May 30, 1998 11:19 AM
To: Tesla List
Subject: Re: New primary test
Tesla List wrote:
> From: Esondrmn-at-aol-dot-com [SMTP:Esondrmn-at-aol-dot-com]
> Sent: Friday, May 29, 1998 11:43 AM
> To: tesla-at-pupman-dot-com
> Subject: New primary test
> Well, it finally quite raining here for a day and I got to do some testing
> last night. The first objective was to compare the new flat primary
> performance with the old 30 degree saucer shaped configuration. The bottom of
> the new primary (3/8" tubing) is setting just even with the first turn on the
> secondary. I had calculated that it should tune at turn 11.5 and the best
> tune turned out to be 11 3/8 turns. The gap started firing at about 125 volts
> on the primary at about 12 amps. The best performance was 56" sparks compared
> to 52" for the old primary. This was with the old 3.3 ohm resistor stack
> (oven elements) in series with the 5000 watt variac used as inductive ballast.
> Primary voltage into the pole transformer was 190 volts at 25 amps.
> Now I ran the same set up only using the new 2.4 ohm resistor bank in series
> with the inductive ballast. Runs good, no cap safety gap firing (set at
Congrats on the end of your cap firing situation!! Good job with the new flat
primary also. My primary is parallel with the first secondary winding also. Sounds
like performance of the flat primary compared to the 30 degree config is near the
same regarding performance, but if you do double your capacitance, you will also
double the joules and will at that time need the extra room you obtained with the
> Let some smoke out of the new 5000 watt variac at 35 amps. This thing
> is rated at 41 amps (new brushes too) and I was surprised to see smoke. It
> did make a hard spot where it was sitting which I will need to sand down. I
> moved the setting a little to make sure the brushes were sitting on a single
> wire and not bridging two. Never happened again and did not seem to be
> getting overly warm. Best performance was 59" sparks at 35 amps with 210
> volts into the primary. I have the ability to drop the series resistance
> still further but I think 35 amps is about max for my current set up. I may
> try the higher voltage tap on the main Powerstat variac some day.
> Basically, I am happy with the performance and am looking forward to adding
> the other .025 mfd cap (thanks to Chip's generosity) in parallel with the
> first one for a total of .05 mfd. Thanks to the suggestions of Bill Wysock, I
> have at least got rid of the firing of the cap safety gap and seem to have the
> primary circuit under control. This seems to be about all I am going to push
> out of this 6" coil.
I would think that if you once obtained 80" discharges, you should be able to do
near that again. I know you have changed quite a few parts now, but wasn't it the
replacement of a failed cap where performance dropped?
> It does make me think that I did have a primary charging resonance condition
> with the old set up. At the same power level that I used last night,
> producing 56" sparks, I used to get 80" sparks. The sparks are hot now
> especially when they hit something but not the same as the thick white bolts
> that I used to get. I guess what you want is resonant charging and expensive
> very high voltage caps that can stand up to it.
> My toroid is 5" x 40". I probably need a larger radius toroid like maybe 10"
> - larger ROC. Would this provide more hold off and thus higher voltage and
> longer sparks?
> Ed Sonderman
Would also like to hear others comments on the toroid. Is this always trial and
error regarding e-field shaping or is there a calculation to predict such a field?