Re: MMC

To: tesla-at-pupman-dot-com
Subject: Re: MMC
From: Raycroft <k.raycroft-at-worldnet.att-dot-net> (by way of Terry Fritz <twftesla-at-uswest-dot-net>)
Date: Tue, 28 Dec 1999 22:28:57 -0700
Approved: twftesla-at-uswest-dot-net
Delivered-To: fixup-tesla-at-pupman-dot-com-at-fixme



Tesla List wrote:
> 
> Original Poster: Terry Fritz <twftesla-at-uswest-dot-net>
> 
> Hi Jason,

<snip>
> 
> 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.
> 

<snip>


After doing a little research, I have found that these will probably
cost more than 100 dollars, and delivery times vary widely.  I was
wondering if anyone out there knows of a good place to get polypropylene
caps either online or retail (I'm near minneapolis, minnesota). 
Preferably cheap and short order turnaround!

Thank you very much for your time,

Jason Raycroft