I would drive them to 1000 volts peak each (realize that I am pretty hard
on caps!! :-)). I have seen 630 volt poly caps take 2000 volts easily. So
that would be a string of 20 to give 50 nF. But the problem is the
current. These cap values are so high that a single string would give a
very high capacitance value such that a single string would have to take
the entire RMS current. Poly caps are good but a single string should only
be pushed to about 3 amps RMS for any poly cap. In most TCs, you need to
run at about 10-20 amps RMS. So you need a smaller value cap and more
strings to handle the current. Forget these caps. Their capacitance is so
high you would not be able to economically use enough strings to handle the
0.1 uF caps at 630 volts would be just like my old MMC. However, it used
160 caps to get 10nF. My latest EMMC uses 20 caps to do the same thing at
a cost savings of $120.
See "old" (November is old now!) 630 volt MMC at:
160 caps to get 10nF. I don't want to look up the price...
New EMMC at:
50 caps to get 28nF. Two strings here would get 10nF using 20 caps. About
Of course, EMMC caps may be real cheap but they rely on caps being
carefully overstressed. Theoretically they should work, but the actual
results are still pending at this time... Mine is only 20 minutes old... :-))
Of course, for even more risk, see my EEMMC (Extra Enhanced Many Multi Cap)
28nF using only 8 caps at $18 dollars. It has put out two foot arcs but I
don't think it would live very long (5000 volts on 1600 volt caps!)...
MMC caps also offer (as John Freau mentioned today) the ability to go to
higher voltages. Since spark length is roughly proportional to primary
voltage, the old limits in cap voltage ratings may no longer be an issue.
MMCs can be configured to any current, voltage, or reliability level with
ease. They can be designed with high accuracy and tests can be easily run
to verify their performance. They are truly taking over the Tesla world in
their few month history!! I think even Nikola would have been amazed at
the MMC caps we now have!
Last year's developments in Tesla coil theory are now paying of in this
year's Tesla coil design technology! I think Nikola would be proud of us!
For me, the biggest advantage of MMCs is that there is no oil. I hate oil!
At 04:39 PM 6/8/99 -0400, you wrote:
>I found a source of MKP1 840, 1uF 630VDC metalized polypropylene caps for
>$1.50, and I was wondering if these would be good for a MMC type cap - and if
>so, how hard can they be overdriven, and in what configuration?