Re: help me put my coil on a diet; its capacitor appetite is expensive!

["Tesla list" <tesla@xxxxxxxxxx>]

Original poster: Esondrmn@xxxxxxx 

Nick,

I snipped a lot here.

Do you have a safety gap across the caps or better yet across the 
rotary or main primary spark gap system?  I also have blown up a 
capacitor or two.  After much head scratching and help from another 
coiler, I added a spark gap across the primary caps set to about 5/8" 
using about 1.5" diameter brass spheres.  I was very surprised to 
discover this new safety gap was firing (loud, like a rifle shot) at 
about 60 or 70% of the main variac setting.  I was experiencing a 
primary resonance problem between the current limiting inductance 
(welder) and the primary caps.  The primary tank circuit voltage was 
going WAY too high and overvolting the caps.  I eventually solved 
this problem by changing the current limiting inductor.  A safety gap 
as I described should not be firing with the 15,000 volt pig 
transformer that I was using.

Ed Sonderman

  The In a message dated 8/31/2006 3:55:32 PM Pacific Daylight Time, 
tesla@xxxxxxxxxx writes:
Original poster: Vardan <vardan01@xxxxxxxxxxxxxxxxxxxxxxx>

Hi Nick,

At 11:25 AM 8/31/2006, you wrote:
>I have now toasted one of my two maxwell's, as well as one of my
>four strands of CDE 940C's. In the interest of not blowing up too
>many more capacitors, I am trying to do my research this time before
>ordering their replacements (and not using any of the remaining
>caps, for this coil anyway).

OK...

>
>unfortunately finding a few roadblocks to that end:
>1. I have a possible source of doorknob caps, in the form of another
>pacific northwest coiler who I recently bought a pole pig from, who
>is going to try to acquire some soon. However, I have heard doorknob
>caps might not be as effective, not to mention they are going to be
>HEAVY to get enough of them for a 25KVA pig powered coil, which is
>using a 120BPS synch rotary.

I can't imagine collecting enough high current doorknobs for a 25kVA
pig system...  You are looking at either MMCs or maybe commercial caps...