Re: NST's shorting out.

["Tesla list" <tesla@xxxxxxxxxx>]

Original poster: Vardan <vardan01@xxxxxxxxxxxxxxxxxxxxxxx>

Hi Martin,

At 06:56 PM 3/20/2006, you wrote:
> ......
>
> "Get MMCs like everyone else ;-))  You might be
> able to just get a smaller value to add to your
> 30nF cap and save some money.  It all sort of
> depends on how you can mix and match it all together."
>
>
> Last question (hopefully!).  Exactly what are MMC's and where can I 
> get them?.  I have heard the term but am not familiar with 
> them.  Are they what are known as "self-healing capacitors?"

MMC stands for Multi Mini Capacitor.  A pretty new type of Tesla coil 
capacitor thought up around 2000.  We take a bunch of small 
2000V,  0.150uF, polypropylene, self healing, 432 peak amps, 13.5 RMS 
amps (70C 100kHz) and put them in series and parallel to make our 
caps:  Series to get to the peak voltage we need an parallel to get 
more current.  MMC love to be run over voltage, but never over current.

http://users2.ev1.net/~nmyreality/tesla/capacitor/mmc.htm

http://www.google.com/search?hl=en&q=%22MMC+capacitor%22&btnG=Google+Search

We all really like the CD 942 types especially the 942C20P15K (we 
worry a little about other types we are not sure of in this super 
hard core application 
http://hot-streamer.com/TeslaCoils/MMCInfo/good-bad.txt ) :

http://cde.com/misc/h942.htm

http://cde.com/film/9422000.htm

http://www.hot-streamer.com/TeslaCoils/MMCInfo/mmcinfo.htm

http://www.hot-streamer.com/TeslaCoils/MMCInfo/GeekCaps/GeekCaps.htm

Dr. Resonance here on the list sells them and they can be bought 
commercially from a number of places too:

http://catalog.rell.com/rellecom/scripts/SkuPage.asp?SKU=162589&PNO=&PNM=

http://catalog.rell.com/rellecom/scripts/SkuPage.asp?SKU=798629&PNO=&PNM=

They cost $2.58 here, but they are going to lead free now and the 
price for those is $3.22 :-((  I am not sure they make the lead 
version anymore...

Here is a chart that says how many to put in series or parallel for 
various NST and gap configurations:

http://hot-streamer.com/temp/MMCcapSales.gif

This chart also uses the 0.100uF caps of the same type.  You can also 
ask around since many of us have extras...

The MMC basically made the old oil rolled caps "extinct" in about 6 
months.  They are very hardy caps and difficult to break.  I think 
like 90% of the new coils use them now.

They can recover from an overvoltage like 100000 times.  We use them 
deliberately at 2000V even though that is sort of rough on 
them.  They make only last 75 hours like that:

http://hot-streamer.com/temp/CD942C20P15K-MMC-Capacitor-Lifetest.pdf

but that is long enough for most of us ;-))

> Again, thanks Terry for your help and patience with all my questions.

That is why we are all here ;-))

Cheers,

        Terry


> Martin