Re: MMC caps: prices, sources, and types

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

Original poster: pepperman-at-softhome-dot-net 

Thanks for the suggestions to try Richardson Electronics!  I looked on
their web site and found several caps I thought might work, and called to
find out more.  It turned out that they only had one of the ones I was
interested in stock (although I guess they could get the others from the
factory), and it looks like they might work!

The ones they had were Arcotronics 2000 VDC .47 uF, metallized
polypropylene.  They're $2.95 each, with a minimum order of 50.  If
anyone else is interested, the phone number is 1-800-348-5580.  Other
capacitances can also be ordered, but they'd have to be shipped from the
factory (I think that means about a week extra wait time).

They also faxed me a spec sheet, and I wondered if anyone could
comment on the specs for these caps--as far as their suitability for Tesla
coils.  Here are the specs for this size of cap:

dV/dt: 700 v/us
IPKR (does this mean peak rated current?): 329 A
ESR max at 100 kHz: 4.8 milliohms
IRMS (100 kHz) -at- 70 degrees C: 12 A

As a side note, the smaller capacitances seem to have a bit higher dV/dt
ratings (1150 v/us for .10 uF) but smaller IPKR ratings (115 A for .10 uF).
Why the tradeoff, and what do the specs mean in terms of performance?
And as far as the .47 uF caps that I gave the specs for, what kind of
performance would you expect?

Michael Johnson