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Re: New cap info
In a message dated 96-12-06 01:45:02 EST, D. Gowin writes:
<snip>
<< While stacking your plate capacitor, use an eyedropper to spread
liberal doses of mineral oil between the poly and aluminum sheets. This will
eliminate those dry spots you spoke of (I discovered this after I had burned
a
development cap I built.). >>
An excellent suggestion and one that I used on the final (up to this point)
build of my cap. I didn't include the plate pre-wetting suggestion in my
original post because I wanted to limit the suggestions to what the designer
mentioned to me in our discussions. I would imagine that pre-wetting each
layer of dielectric by hand prior to assembly would not be practical from a
labor/production standpoint but it makes a great deal of sense for an
individual cap builder without access to a vacuum pump.
<snip>
>The above technique can be messy but it works. Oh by the way, what does
>your friend at the cap factory want for his HV capacitors?
>
>For example:
>
> 0.1 uF 100 KVDC $?
> 0.01 uF 100 KVDC $?
> 0.001 uF 100 KVDC $?
>
>Last:
> Always remember and never forget, why coilers build homemade caps in
>the first place. $
<snip>
The caps that Plastic Caps sell for TC and pulse discharge use are rated for
AC not DC as you list in your post so I'm not sure what the equivalent
voltage ratings would be to answer you question. I can tell you that they
unequivocally recommend to *never* use a cap which is rated for DC use (at
*any*) voltage for high frequency AC use as heating and major losses will
almost always result as dielectric materials that are routinely used for DC
purposed invariably have a very high "dissipation factor" at TC frequencies.
This will inevitably result in considerably less output form your TC than if
you use a high frequency rated AC cap. I can also tell you that their .01mf
-at- 15kv AC cap (which is the one they recommend for 12kv or 15kv neon TC use
was $155.00, which compares quite favorably with the cost of the one I built:
$50.00 for the (4) 4x8 sheets .03in polyethylene
$30.00 for the 1/2in plexiglass for the case
$12.00 for the (10) 8in lag bolts, washers, nuts & locknuts for the case
$50.00 for the gallon of silicone oil
$3.00 for the heavy duty aluminum foil
$4.00 for 100 sheets drawing paper for wicking
$8.00 for the (2) 12inx14in butyl rubber gasket for the case
$1.50 for the 1in OD acrylic tube riser
$1.00 for the rubber/plastic pressure relief plug (to fit over the riser)
$15.00 for various drill bits for drilling the plexi
Total: $174.50
It would have been cheaper and much less waste of time and energy for me to
just buy a comercial one in the first place... but I wouldn't have learned as
much about cap theory, design and construction as I did. I would suggest to
any one to build one first for the experience and then buy one for the best
performance!
By the way, when I switched to the commercial cap, performance (output) of my
coil jumped by at least 30% (from 2ft to 3ft streamers). I consider the
purchase *well* worth it.