Re: MMC or Maxwell? Which is better?

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

Original poster: Mark Broker <mbroker-at-thegeekgroup-dot-org> 

Actually, caps would have to be added in series as well....

In my MMC and TC designing efforts in the past, I have found that smaller 
NST coils tend to stress MMCs more with respect to instantaneous 
current.  The larger TCs, particularly with higher break rates, tend to 
have a lower peak current per string, but a higher RMS current per 
string.  The official peak current rating of the 942C20P15K is 432A per 
cap, which is fairly easily exceeded by a factor of 2 or 3 on an NST coil 
(single string, low primary inductance).  On the other hand a 5kVA PDT coil 
will require maybe 5 strings, increasing the peak current rating to 2100A - 
considerably higher than the peak current JavaTC gave me the last time I 
"designed" a ~5kVA TC with it.

So I would argue that an MMC offers more than adequate current rating for a 
larger PDT tesla coil and that a commercial pulse capacitor will not offer 
a significant (or any!) improvement over a similarly-rated MMC (or even 
under-rated MMC, as is the "trend").  The disadvantage of an MMC for a 
larger TC then, in my opinion, is the physical size of the MMC and the time 
it takes to construct.

Of course, *opinions* seem to vary at this point, so I would be interested 
to know if anyone has done a direct comparison between a "GeekMMC" and a 
commercial pulse capacitor, particularly on larger TCs.  Several people, 
including the esteemed Dr. R, have cited the "breakeven" figure of 5kVA, 
and I'm curious to know how that number was arrived at.

Best regards,

Mark Broker
Chief Engineer, The Geek Group



On Fri, 27 Feb 2004 07:26:41 -0700, Tesla list <tesla-at-pupman-dot-com> wrote:

>Original poster: "Virtualgod" <mike.marcum-at-zoomtown-dot-com>  >
>With respect to the question at hand: which is better, I must mirror Dan
>M,
>  > Matt D, Terry, and Dr R's comments.  There is no question that an
>  > appropriate commercial pulse cap has higher current ratings than an MMC,
>  > but an MMC will cost significantly less in most circumstances and deliver
>a
>  > similar performance to a commercial cap.
>
>Of course you could just add more strings (~8Arms/430Apk each) to the MMC
>till the current is higher than the pulse cap, though I'm not sure if the
>cost would still be cheaper than a pulse cap.
>