Ignoramus27088 wrote:
Got myself some capacitors for $10 apiece.

http://cgi.ebay.com/ws/eBayISAPI.dll...tem=7603382621

The specs are 22 kV, 1 uF, discharge capacitor. See

http://igor.chudov.com/tmp/cap.jpg

The seller was wrong in describing them as 22 VOLT capacitors. They
are 22 KILO volt capacitors. (the seller is Fermilab).

They are similar to this one:

http://cgi.ebay.com/ws/eBayISAPI.dll...tem=7598631638

but have twice more capacitance.

Anyway, here is my question. I have a 9 kV DC power supply. (a
Franceformer). How can I safely test these caps before selling
them. At 22 kV, they can store about as much energy as a .22 bullet,
according to my calculations.

It would be less at 9 kV, but still, obviously, very deadly.

So. What is a safe way to charge them, verify that they hold the
charge, and then DIScharge them at 9 kV.

i



Why hasn't anyone mentioned yet that if you DO get a HV probe for your
meter it will serve as a resistor to discharge those caps.

It will take a while, but you can observe the progress on the meter it's
hooked up to and when the voltage gets down to something that won't jump
out and grab you, an easier to obtain lower voltage rated resistor can
be used to pull them the rest of the way down quickly.


MAKE SURE you watch out for "dielectric adsorption" which is the
property of some capacitors to "recharge themselves" when left open
circuited after you've discharged them. Needless to say, that effect can
make for some nasty suprises. To play it safe, I'd leave a shorting link
or low value resistor connected across them after they're discharged.

Know anyone with a small Van DeGraf generator you could borrow? One of
those could probably charge up those caps slowly enough for you to watch
the voltage rise on the meter, and you could turn it off when you got to
20 KV.

Just my .02,

Jeff

--
Jeffry Wisnia

(W1BSV + Brass Rat '57 EE)

"Truth exists; only falsehood has to be invented."