Re: Awesome Quarter Shrinking Capacitors on EBAY

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

Original poster: "Jim Lux" <jimlux-at-earthlink-dot-net> 

 >  > Surplus capacitors like this, of uncertain provenance, from catalog
dealers
 >  > (e.g. C&H sales) run a few hundred dollars at most.  For instance,
 >  > Alltronics (up in the Bay Area) has some Aerovox PX15QD58 caps 7.14
uF-at-50kV
 >  > for $295 each.  That's 9kJ. The picture looks like it's a bit ratty
(like
 >  > it's been sitting on a wooden pallet or wrapped in plastic. A Sangamo
14 uF
 >
 > Interesting. I apparently have two of these Aerovox caps, though not from
 > this dealer. They were $75 each from ebay as I recall. They are made in
 > 1980 and 1981, all paper construction, the high voltage terminals are
 > crumbly but seem to have survived a few dozen shots. Mine arrived with no
 > grey lacquer left at all (rusty), but it's no big deal. I have no way to
 > know if they are used, or old stock.
 >
 > Modern equivalents are about half the size/weight from what I gather.

Actually, much better... The standard squarish can (12x12x29) was 6kJ using
kraft paper/oil.... These days, you can get 100 kJ in the can..

This raises a significant problem.. 6kJ is an energy that can be contained
by the steel box forming the cap...so, if an internal fault develops, the
explosion won't be that spectacular...
However, 100 kJ is not something you can hold in, so internal failures are
MUCH more spectacular. I've heard stories (but not actually seen) about
tests with caps exploding... at these energies, the fuses are to protect the
cap from the other caps in the bank, rather than to protect the single cap.
Imagine 50 of those puppies in parallel.... (Project Sherwood...)

These days, I think they use Compulsators for Megajoule energies.... Except
perhaps in multimarx setups like the Z-machine.