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Coil Specs
cc: tesla-at-grendel.objinc-dot-com
Scott Meyers,
Here are the specs on my coil:
Secondary: 6.25" dia, winding 27.6" long, calculate 986 turns, measures 32 mh
Primary: 14 turns 3/8" copper tubing wound at 30 degrees, calculate 86
microhenries at 14 turns, measure 82 microhenries. Calculate 59 microhenries
at 12 turns.
RF bypass caps, homemade: approx 690 pf each.
RF chokes, homemade: approx 675 microhenries each.
Original homemade rolled oil filled tank capacitors: approx .019 mfd each
(2)
With the original 14 " dia x 4" thick toroid and two tank capacitors in
series the coil tuned right at 14 turns. Calculated frequency with two caps
in series is 185 khz. With one capacitor it tuned at about 12 turns and I
measured 187khz when it was operating - I calculated 154khz. There is quite
a bit of difference between the calculated operating frequency and the actual
frequency here, this data is from my notes - must be something off somewhere.
With the 33" dia x 5" toroid and one capacitor the coil tuned at 13.25 turns.
The measured operating frequency here was 138 khz and I calculated 137 khz (
much closer this time). I have to tell you these capacitors will not survive
at 12kv unless they are used in series. When used one at a time they will
break down - I eventually lost them both. I would run them at 9kv max, and
even then not feel too comfortable.
All of the above data is with a cylindrical static gap and neon sign
transformers for power. I have since gone to the 14,400 volt 5kva pole pig,
controlled by a 28 amp powerstat variac with an arc welder in series for
inductive ballast with 6000 watts of oven elements in parallel with the
welder. I am using a rotary gap with a 10" dia lexan disc with 16 electrodes
and I run it in series with a folded static gap. I estimate the rotary speed
at 4000 rpm. I haven't made any frequency measurements since I started using
the 40" toroid. I believe I am getting 72" plus discharges now at about
8kva. I should get some better numbers when I get it set up outside.
Ed Sonderman