Re: MMC cap questions

[Esondrmn-at-xxxxxxx (by way of Terry Fritz <twftesla-at-xxxxxxxxxx>)]

In a message dated 11/9/00 3:15:24 PM Pacific Standard Time, tesla-at-pupman-dot-com 
writes: 


>
> Hi all, 
>
> My NST farm is dwindling, and I'm looking at pig-power.  I feel confident in 
> my knowlege to move up to the multiple kva niche and start experimenting. 
> Though I want to choke the system down to only ~2 kva to start with, then 
> move again as I learn more.  8" coils are much more expensive to wind than 
> 2" coils ;)  Mostly, I want a more robust power supply, but having more 
> power is always welcome.  Something externally ballasted will give me the 
> ability to run 2kva or 20kva. 
>
>    Now, I currently have an 80nf tank cap (16 strings of 11) MMC.  If the 
> panasonic caps go nuclear at ~3A RMS, I think I can push 32A rms without too 
> much trouble.  Think this will stand up to a pig's abuse?  Voltage-wise, I 
> know it's under-rated, but I can always use a small step-down tranny on the 
> 240v side to lower the pig's output to 12kv.  Only have to reduce the line 
> voltage to 200v (maybe a heater element in series to burn off some voltage). 
>
>  What concerns me is the RMS current.  The caps take over-volotage in 
> stride, but over-current is murder on 'em. And I'd hate to burn up $230 
> worth of caps by not knowing... 
>                                            Sundog 
>
>



Sundog, 

Not sure about the current capabilities of your caps.  Terry can probably 
help with that.  You can always control the maximum voltage by not turning 
the variac all the way up - and you definitely need to use a variac with a 
pole transformer powered system.  I would reccomend using some resistive 
ballast in the range of .5 to 1.5 ohms in series with some inductive ballast 
- either another variac, welder or home made ballast which could be many 
turns of #8 or #10 wire wound on a suitable iron core.  This could have 
several taps to allow changing the primary current. 

Ed Sonderman