Re: MMC ratings

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

Original poster: "Mark Broker by way of Terry Fritz <twftesla-at-qwest-dot-net>" <mbroker-at-thegeekgroup-dot-org>

 >Geek group caps have been tested to 5700 volts before breakdown and then
 >they self heal and are good to go again.  Panasonics go to 3600 volts.  I
 >really don't feel the voltage is a problem at all with MMC caps.  The real
 >area of concern is current and internal heating.

The only failure I'm aware of, aside from Chris Robert's, was attributed to 
overcurrent.  That
was about 18 months ago, and I can't recall a single detail about it since 
I was on vacation
at the time. :(

In my last email, the third failure was Terry's destructive testing of a 
cap we sent him,
shown in the quoted link below.

 >http://hot-streamer-dot-com/TeslaCoils/MMCInfo/mmcinfo.htm
 >
 >I used to send a printed copy with each MMC cap order in the good o'l
 >days.  I also sent along 10Meg resistors for free that were also trouble
 >free over the years.

I believe the MMC sales page on our site has a copy of that sheet.


 >"I" would run Geek caps to 4000Vpeak in an EEMMC design and I bet they
 >would work just fine ;-))  I also bet I know a few things about poly caps
 >that most of the manufactures don't know :-))  However, Cornell Dubilier
 >has done a few tricks to extend the art even further!

Likewise, for my own coil, I would use 2500 to 3000V, since I'm not as 
daring as Terry. ;)
But for a coil I would build or design for someone else, I would use no 
less than what is on
the MMC Design chart I put together.

I believe there are plans to replace the design chart with a Javascript 
design calculator with
a selectable "ratings" option.  This will also allow the design to be 
scruitinized for current,
which isn't really possible in a static chart.

One of these days I'll tear apart one of these caps to learn firsthand 
these "tricks" CDE
uses. ;)

The GeekMMC Design Chart was created using the "generally accepted" voltage 
ratings for
MMCs and MMC caps.  Since the CDE caps test better than the Panasonics, I 
would
argue that the GeekMMC Design Chart actually has better voltage ratings 
than an
equivalent design using Panasonic caps.

Mark Broker
Chief Engineer, The Geek Group