Re: Started winding today....
After much research and many questions, I built my rolled poly caps
after Mike Hammers' design.
I have a 15K/60mA NST so I needed .0107 uF cap. More layers of poly are
better, thinner layers give you better capacitance. I decided to roll 3
caps wired in series, each = to .033 uF each. I used 4 layers of .006
mil poly/aluminum foil/4 poly/foil. The poly was inexpensive roll from
Home Depot (a 10' X 25' roll made all three caps).
For the terminals I just used some of the heavy duty aluminum foil. I
cut a 3' piece, folded it in half so it was 18", then folded and folded
lengthwise until it was 18" X 1" (with all those folds it was very
stiff). Then I taped one to each piece of foil with extra length
extending out, when rolled up and held with ties, these straps conduct
Rolled up tightly, nylon ties to hold it, the caps fit perfectly in a 3"
PVC pipe. As mentioned earlier, I didn't have a vacumn pump at the time,
so I used an upside down palm sander and vibrated air out of it. I have
had absolutely no problems or punctures with these caps.
> I have built two rolled poly caps and lost them both due to overvoltage. I
> also used only one layer of .062 poly originally. Two .030 layers would be
> much better and three .020 layers would be even better. In my opinion .062
> poly is only good up to about 9 or 10 kv and will fail at 12 kv. I think
> three layers of .030 for .090 total is good up to 12 kv (talking ac, rms
> and I think you need either four layers of .030 for 15 kv or perhaps six or
> more layers adding up to .090 total.
> What experience have others had in this area?
> Ed Sonderman