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


Unmless you are going to test them to 80% of their maximum voltage
rating or to their full working voltage, I wouldn't describe them as
tested for resale. You'd be better off checking them at say 1KV and
then selling them as untested but belived working with a (short) warrenty.

I wouldn't even want to ship or store them without shorting straps
accross each one.

If you do decide to do the high voltage testing, a TV LOPT commonly
operates at up to about 27KV but the tube has typically 1/100 of the
capacitance. A TV EHT probe or meter is easily capable of measuring
these voltages safely, though personally I'd want to set it up in a
grounded clamp stand so I wasn't hand holding it.

Discharging them safely is going to be a real problem. The obvious
approach is a series chain on high voltage high power resistors in an
insulating tube that is good to at least 30KV. Maybe a chain of bleeder
resistors from microwave ovens? However I'd want specialist advice
myself. Why not ask on sci.electronics.repair. Do you have a drum of
suitably rated EHT cable? If not you cant really make ANY connections
safely to them.

--
Ian Malcolm. London, ENGLAND. (NEWSGROUP REPLY PREFERRED)
ianm[at]the[dash]malcolms[dot]freeserve[dot]co[dot]uk [at]=@, [dash]=- &
[dot]=.
*Warning* SPAM TRAP set in header, Use email address in sig. if you must.

"Ian Malcolm" wrote in message
...

Discharging them safely is going to be a real problem. The obvious
approach is a series chain on high voltage high power resistors in an
insulating tube that is good to at least 30KV. Maybe a chain of bleeder
resistors from microwave ovens? However I'd want specialist advice myself.
Why not ask on sci.electronics.repair. Do you have a drum of suitably
rated EHT cable? If not you cant really make ANY connections safely to
them.

It's really, really fun to drop them in a bucket of water while fully
chargedG.

Actually, it doesn't do much, but you get a nice crack and a cloud of steam
each time.

We did that at the Transitron lab because the engineering department was too
cheap to spring for a high voltage bleeder array. Not that it would've
cost much, but they didn't want to use up "valuable bench space".

Now... dropping a wet paper towel across the terminals -- THAT's fun!

LLoyd

For some reason to do with silly things to do with science this reminded
me of the glass phenomenon called "prince rupert drop"
http://en.wikipedia.org/wiki/Prince_Rupert's_Drop , if you see a glass
blowing demo then ask about it maybe they will show you. If your brave
then have one go of in your hand, numbs it for a minute or so but much
like catching a baseball incorrectly.

Lloyd E. Sponenburgh wrote:

"Ian Malcolm" wrote in message
...

Discharging them safely is going to be a real problem. The obvious
approach is a series chain on high voltage high power resistors in an
insulating tube that is good to at least 30KV. Maybe a chain of bleeder
resistors from microwave ovens? However I'd want specialist advice myself.
Why not ask on sci.electronics.repair. Do you have a drum of suitably
rated EHT cable? If not you cant really make ANY connections safely to
them.


It's really, really fun to drop them in a bucket of water while fully
chargedG.

Actually, it doesn't do much, but you get a nice crack and a cloud of steam
each time.

We did that at the Transitron lab because the engineering department was too
cheap to spring for a high voltage bleeder array. Not that it would've
cost much, but they didn't want to use up "valuable bench space".

Now... dropping a wet paper towel across the terminals -- THAT's fun!

LLoyd