[Prev][Next][Index][Thread]

Capacitor construction?


Greetings!
  
I recently obtained a 12kv 30ma NST to use for my TC.
Before I started putting things together I wanted to post
the specs I am currently planning on using, to see if anyone
notices any obvious problems or miscalculations.
  
Here are the details:
  
Transformer:       12kV 30mA NST (no power factor correction)
  
Primary:           1/4 copper tubing, 21" od, 6.75" id, 8 turns
  
Secondary:         4" x 10.75"  ~54 TPI  ~0.014" wire (75% spacing?)
  Calc. Freq:      660kHz (currently no top capacitance)
  Planned Toriod   4" id, 8"od, ~3pF (drops frequency to about 530kHz)
  
Tank Cap:          (Until I have a toroid)
                   90 mil poly (20 layers 4.5 mil stock)
                   105 in^2, 6 plates, ~0.0029uF  13kV rating
  
Tank Cap:          (After I get the toroid)
                   90 mil poly(20 layers 4.5 mil stock)
                   105 in^2, 9 plates ~0.0046uf   13kv rating
  
Spark gap:         1/2"x4"(x2) steel ground rod, ends ground flat
                   spacing unknown
  
Safty gap:         dunno yet
  
  
Questions:
  
On the primary I only have 8 turns, I have enough tubing for a few more,
shall I go ahead and inish off the coil with the remaining tubing?  (just
have to buy some new wood to mount it on).
  
For the tank cap I only have some 4.5 mil black construciton type plastic
(but I have LOTS of it).  I figured a voltage rating of 450v/mil, with 20
layers
to get to 90 mils (and help to protect defects), and a voltage rating safty
factor of 3 would give me a cap that could handle about 13kV total.
Six plates should give me about 0.0029uF, and later, after I get the
toroid I can add three more plates to get to 0.0046uF.
Anybody see any problems with this?
When I have some money I may buy some clear plastic, but for now
I'm stuck with this stuff.
  
There is a web page out there somewhere that offers smooth copper
spheres up to several inches in diameter for pretty reasonable prices.
I can make a toroid up to about 8 inches in diameter, but its surface
won't be as smooth as the copper sphere.  Which would be a better
option for this size coil?
  
What should I set the spark gap to initally?
  
What should I set the safty gap to?
  
Thanks!
  
David Knaack