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Re: MMC

Hi Jason,

	Some door knob caps can be used and some can't.  Most are made for DC
filtering and don't like RF.  There are true high power doorknob caps out
there but there price is super high (like $100 each).  All Tesla coil caps
we talk of are full AC rated caps.

MMCs do not use door knob caps but use fairly common polypropylene caps.
By stringing them together in series you can get high voltages and by
paralleling them you can get high current ratings.  Most people use a 1/2
watt 10Meg ohm resistor across each cap for safety (drains it quickly) and
it keeps the voltages balanced across the long strings.

MMCs do not have to be over rated.  Your 15kV transformer will peak at
around 21kV and that is all you need to rate MMCs for.  We have run MMCs
well beyond the safe point with great results, so they are not nearly as
fragile as older caps.  In fact, if a cap in an MMC shorts it will self
heal and still be as good as new (a wonderful trick the cap manufacturers
came up with).  Poly caps actually fail at about 2.5 times their voltage
rating.

Since MMCs have many strings, it is easy to select as many as needed to get
different capacitance values.

Here are a few pages that detail their construction.  There are many more
but these are the ones I had handy:

http://www.peakpeak-dot-com/~terryf/tesla/misc/MMCPower4.html

http://www.peakpeak-dot-com/~terryf/tesla/misc/ltr/

http://people.ne.mediaone-dot-net/lau/tesla/mmc_cap.htm

http://www.peakpeak-dot-com/~terryf/tesla/misc/phe428.pdf

http://users.better-dot-org/roverstreet/components/cap.html

http://tesla.better-dot-org/mmc_form.cfm

Cheers,

	Terry

At 11:46 PM 12/26/1999 -0600, you wrote:
>I'm a relatively new coiler (1 year of research, finished first coil
>last month, 4x16x22awg sec, sw cap and 15/30 nst), and after seeing lots
>of blue glow from my sw's, I would like to try an MMC.  I was just
>wondering where one can get "doorknob" caps.  Are they for AC, or do I
>need to rectify nst output?  How big should resistors be?  Basically,
>just what is the average MMC and what design considerations should I
>make?  For easy configuration, I would like to build several .001uF caps
>rated at about 30kv.  This way I could use as many in parallel as I
>need.
>
>Thanks for your time,
>Jason Raycroft
>