Re: big cap - safety concerns

["Tesla list" <tesla-at-pupman-dot-com>]

Original poster: "Bert Hickman by way of Terry Fritz <twftesla-at-qwest-dot-net>" <bert.hickman-at-aquila-dot-net>

Shaun and all,

All HV Capacitors are NOT created the same. Based on it's previous
application, I would guess that the type you have is not constructed to be
a high current, low inductance pulse capacitor, but more likely is
constructed as a filter cap that's been pressed into service to provide
moderate (ampere level) current for a pulsed x-ray system. If it's got big
ceramic feedthrough insulators, chances are it's not a true low-inductance
pulse cap. Low inductance high energy pulse caps will typically have low
profile, flat, large diameter insulators (to reduce inductance) and very
large studs (typically 1/2" - 3/4") to handle the surge current.

Can crushing and coin crushing typically require pulse current in the 30 -
120 kiloampere range... unless your caps are built to withstand the
resulting ringing (can crushing) and the internal electromagnetic and
hydrodynamic shock created by high energy discharges, plan on them failing
fairly quickly... perhaps violently. A 5000 joule discharge packs the same
amount of energy (~3700 foot pounds) as dropping a 900 pound weight from
over 4 feet. This is NOT a trivial amount of energy - and it's truly
explosive when discharged in 10's of microseconds. 

Shaun, these devices are like small bombs - they will physically remove
pieces from you if given half a chance. Unless you are VERY familiar, and
have significant experience in working with high voltage AND high energy
sources, consider leaving them uncharged. Make sure you have a bleeder
resistor or shorting wire across them at all times. If you decide to try
charging them, be SURE you have a way to safely discharge them (shorting
them with a wire or screwdriver is NOT a safe way!). And plan to contain
the cap so that if (or when) it fails, you'll not have 10 gallons of oil on
your floor when the case ruptures. Been there, done that...  :^(

Best regards,

-- Bert -- 
-- 
Bert Hickman
Stoneridge Engineering
Email:    bert.hickman-at-aquila-dot-net
Web Site: http://www.teslamania-dot-com

Tesla list wrote:
> 
> Original poster: "Shaun Epp by way of Terry Fritz <twftesla-at-qwest-dot-net>"
<scepp-at-mts-dot-net>
> 
> Well I'm not going to critic  math :-))
> 
> But,
> 
> I have also pulled apart an impulse xray machine and inside it is a dual
> (two in one can) 2uF 50Kv DC capacitors and it weighs lots.
> (there was also 10 gallons of smelly transformer oil that I had to drain out
> before I could get to it)
> 
> QUESTION:  What can we do with a big capacitor like these.  4uF -at- 50Kv
> works out to 5000 joules of energy storage capacity.   WOOFF !!!   They were
> series connected for 100 Kv and current limited by two 2Kohm resistors.
> That works out to ..... 25 amps peak current (big deal).
> 
> can these oil filled caps be used in a can crusher or another neat project.
> Any input would be appretiated.
> 
> Thanks for the replies in advance.    :-))