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Re: Calling Bart Anderson
Original poster: Vardan <vardan01@xxxxxxxxxxxxxxxxxxxxxxx>
Hi,
It helps to imagine a "giant" MMC... Lets take a 1000 x 1000 array
to explore the "limits"...
It can store 300kJ!! Better use drain caps on each one - or column
#167 and row 637 might kill you if you go digging around in there
;-)) I always advocate drain resistors, and I always will...
Read and understand the tips about 60% down the page at:
http://hot-streamer.com/TeslaCoils/MMCInfo/mmcinfo.htm
Since you are spending $2,580,000 on leaded or $3,220,000 on unleaded
caps in our fanciful case, you don't want to make any simple known mistakes!!!
Along those lines, consider that a commercial cap rated for the use
might be cheaper... The usual sources of new and used caps should be
considered... MMCs are wonderful for normal coils, but if the cap
quantities get into the hundreds, a commercial cap might end up being
cheaper...
Our funny cap is rated at 150nF, 432,000,000 peak amps and 13,500,000
RMS amps at 2,000,000 volts. You probably will not break it
;-)) Inductance increases with string length, but divides with
parallel strings... A "wash"... But a "serpentine" construction
will cut down on "loop area" that defines such inductances in large
array cases... My SISG PIRANHA coil's firing section is fully serpentine...
In general, I think you really will have to solder on those 1,000,000
resistors... All will argue, but at the end of the day, I know
exactly the remaining voltage on all "my" caps ;-))) The killer is
the DC voltage components due to leakage and such...
You would benefit from really knowing the RMS and PEAK currents
needed to see if you are not just wasting cash on too many
caps... Programs like ScanTesla will tell you those numbers...
http://drsstc.com/~scantesla/scantesla810.zip
So party hardy... I think your biggest concern is the cost of MMC vs
the cost of commercial...
Cheers,
Terry
At 07:06 PM 11/6/2006, you wrote:
Hi Jim,
Wow! That's a BIG MMC! I think that large MMC's are fine from an
electrical view point. I'm not sure that price is however.
Professional pulse caps can be found from time to time for a great
price. New ones are spendy however.
I feel your ok with the voltage standoff rating. As long as you are
at least in the "fair" range, your ok according to the TCML's
experience with MMC's. "Fair" indicates the cap bank is rated
between 1.5 to 2.0 times the transformer peak voltage. That's decent
for MMC's and most MMC's are built in this range. Some have managed
long life with no derating (the cap bank voltage equal to Vp). Note
that Javammc gives a "questionable" rating here. I know the talk
about MMC's current and temp data, but I still feel it's worth the
extra money to at least give some derating to the caps regarding
voltage which is why I give both a voltage and temperature rating in
Javammc. I realize that with a large cap bank, the extra money can
be quite a bit. For the average MMC, it's reasonable.
I don't want the program (Javammc) to error on the side of failure,
but to error on the side of success.
I've been thinking that maybe the derating "values" would be more
helpful than "words" (i.e., "fair", "good", etc.). The reason I kept
the word format is for new experimenters who may not be as familiar
with capacitor derating during protocols.
What do you think, would numbers mean more than words to you? (they do to me).
Take care,
Bart
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