Terry's DRSSTC - Buss cap damage...

["Tesla list" <tesla@xxxxxxxxxx>]

Original poster: Terry Fritz <teslalist@xxxxxxxxxxxxxxxxxxxxxxx>

Hi All,

> So I cranked it up into a bare primary circuit with about 3 ohms of 
> resistance:
>
> http://drsstc.com/~terrell/pictures/NewBridge-01.gif
>
> Note that the voltage driving square wave is super clean!!  Almost "too" 
> clean...  It started out clean with the last bridge too, but then got 
> noisy...  Hmmmmmmm  ?;-|  I wonder if there was some damage to the old 
> bridge I did not detect...  Gee whiz, I checked and double checked 
> everything...  Think more on that...  But clean is good for now ;-)

So I tore apart the old 4.7uF 600V 940C 6W4P7K CD buss cap I still had, and 
a brand new one......

I first noted the old one had an odor of "fried chicken" ;o)) I only have 
my new Buck 277 hunting knife and my Channellock 349 linesman's plier here 
tonight... But I think I see the end plate connections on the old cap are 
"fried"...  I think, "again", those weenie "metalized film" caps have let 
us Tesla coilers down as we push thousands of amps through them :o)))

I'll see if I can check it out on the fancy scope stuff at work tomorrow, 
but it looks like you really want to bypass those buss caps good with lower 
value high dV/dT caps!!!  Electrolytics probably look "open circuit" and 
metalized poly caps probably fry...  We need to conduct the "crazy 
currents" around them...

These IGBTs, driven hard, have "terrible" dV/dTs and dI/dTs...  We have to 
have darn good caps right there in the buss to take that crap...

Hope we don't have to got to those $16.00 (each!!) ruby/sapphire 
caps...  But my new H-bridge board 
(http://drsstc.com/~terrell/pcbart/H-Bridge-01.gif) has holes drilled and 
ready :o)))))

Bwahahhahahha!!!

Cheers,

        Terry