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Latest MMC Calculations...
Hi All,
I use MathCad to do most of my MMC calculations. I can easily try
different things and see the results immediately. I have posted my latest
and greatest MathCad file (version 6.0) at:
www.peakpeak-dot-com/~terryf/tesla/misc/MMCcalc.MCD
For those that do not have MathCad, I have also posted the equations at:
www.peakpeak-dot-com/~terryf/tesla/misc/MMCCalc1.jpg
along with the definitions at:
www.peakpeak-dot-com/~terryf/tesla/misc/MMCCalc2.jpg
These equations have the life estimates for corona, temperature, and Dv/Dt.
The temperature and Dv/Dt life estimates are from reading between the
lines of a bunch of data and they contain a lot of arm waving but they
should be somewhat close.
A great file with metalized cap data from Evox-Rifa that has thermal and
Dv/Dt data for the calculations is at:
www.peakpeak-dot-com/~terryf/tesla/misc/phe428.pdf
It would be nice to have some program that would simplify all this like a
(spreadsheet or something) that could calculate a large matrix of cap
combinations and find the best price, lifetime, etc. but I have not figured
out a graceful way to put this all together. Also things are changing
daily but a single program that we all could use would sure be nice...
hint, hint :-))
BTW - Many manufacturers say that when the cap value has decreased 5% from
the original value it is at end of life. Apparently, metalized poly caps
can take up to one million (!) arcs before they are dead. There are a few
hints that a cap will decrease in value initially and then reach a plateau
for a long time before going bad... If you have an MMC without shorting
resistors, be darn sure the cap your are measuring is totally discharged
before connecting your LCR meter to it!
Cheers,
Terry