Re: MMC Caps
At 10:15 AM 02/16/2000 -0600, you wrote:
>I've been out of the picture for a while, and I'm sure you get a a lost of
>posts about MMC caps, but my curiosity is up.
We have you been all year!?! :-)))
>I was doing my calculations for making a rolled poly cap, and geting the
>necessary vacuum components together when I got Terry's post about the
>QBasic program and investigated some of the photos on his site. MMC caps
>sound like an order of magnitude easier to make. But tell me:
We have discussed MMCs, that have dominated Tesla capacitors, all this
year. You may have missed a lot!! You could pour over the archives for
days but let me fill you in...
Multi Mini Capacitors are where a bunch of small capacitors are wired in
parallel and series to make one big cap that has a very high voltage and
current rating. We use metalized polypropylene capacitors that have very
low loss. They will actually easily recover from over voltage spikes. We
have found them to be absolutely wonderful for TC use. They can easily
recover from over voltage (to a point) and we can run them at or over their
DC voltage rating without problem. We have pretty well figured out how to
rate them for current too. I, and others, did a lot of destructive testing
and they have proven to be great!! People have tried this in the past but
today's high-tech poly caps were the key to getting them to finally work.
> a). Do they perform as well?
I would bet that they will easily out perform any other cap. There AC loss
is about 60 milliohms more or less. If they were perfect, you would not
notice the difference.
> b). Are they sufficiently durable?
Yes! Many of us push them right over the edge of their specs without any
trouble. You can over design them with ease but you may be wasting money.
There are also EMMC (enhanced) versions where we wildly throw specs to the
wind and push them right to the limit. They "usually" still work and they
can be made with the minimum number of caps which saves money. My program
rates caps as to how "safe" they are in different combinations vs. cost.
> c). Are they actually easier to construct?
You have seen mine. I can put one together in about an hour with only a
soldering iron. If you make a fancy box and stuff it takes longer but the
main guts really are as simple as they look.
> d). How are they contained? (oil bath?)
Nope! I just mount them on perfboard in air. They need a little space
between each for cooling.
> e). Are they too good to be true?
Yes, they really ARE perfect! They do cost a little real money but other
than that, they are trivial to make and work better than any other cap out
there. They can also be made right to the size a coil needs with little
wasted effort or money.
>Should I go out and buy my poly, or build an MMC? Thanks for any info!
A number of people abandoned their poly cap projects to go to MMCs. I
think they were all happy they did. I will have 1000 caps here tomorrow
(like 20 pounds worth ;-)). I sell them at my cost if you need any... I
also have the resistors (free) and perfboard (pricey cause I get the good