Re: huge "quarter shrinker" caps on ebay for $50 each!

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

Original poster: "Bert Hickman" <bert.hickman-at-aquila-dot-net> 

Tesla list wrote:

>Original poster: DRIEBEN-at-midsouth.rr-dot-com
>Hi all,
>I had to pass this one on to the list. This would be one heckuva
>deal for anyone in southern California. Go to ebay item# 3848857633
>to see the 17.5 kV, 72 uFD GE caps for $49.99 each. Gosh, sometimes
>I wished I lived in CA as it seems that about 90% of the good deals
>on big stuff like this are located there. Being in TN, the freight/
>shipping charges would kill me ;^(((
>David Rieben
>
>.

Hi David,

Interesting caps. They would be great for many lower energy pulse 
applications. However, judging from their appearance, these caps are 
probably NOT going to be suitable for very high current applications such 
as coin shrinking. One giveaway is the long "Frankenstein" insulator. This 
style of insulator is not used on ultra-low inductance, high current energy 
discharge caps. Ultra-low inductance caps will use a large diameter flat 
insulator instead of the longer style to minimize inductance. For example:
http://205.243.100.155/frames/gallery/capbank3.jpg

BTW, I originally used a batch of 54 uF 15 kV GE polypropylene "pulse" caps 
that had similar style insulators in the first quarter shrinker. 
Unfortunately, these caps began failing after relatively few shots. One 
capacitor failed catastrophically. An autopsy of the failing unit revealed 
a major design flaw: one of the internal copper strap bus bars had a 
hairpin loop. Under high current pulses during coin shrinking, magnetic 
forces would try to open up this loop. Under repeated stressing, the bus 
bar actually began to rip away from the capacitor rolls. After about 50 
shots major damage had occurred, and finally the hydrodynamic shock from 
one of the internal arcs ripped open the steel case. And the resulting 
hemorrhage of stinky, yucky arc-blackened oil all over the floor was a real 
hit with the wife... :^/.

Best regards,

-- Bert --
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