RE: First high Power session since '99

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

Original poster: "Dave Hartwick by way of Terry Fritz <twftesla-at-qwest-dot-net>" <ddhartwick-at-earthlink-dot-net>

Terry,
I was discussing MMC caps (teeny-weeny) with tongue partially inserted in
cheek. Indeed, I have fired this 4" secondary with  a bank of 30 Panasonic
ecw-h caps (0.0054 ufd total) and 15/60 NST power. They were extremely
impressive on a rather crude, probably overcoupled system. I even commented
to John Freau in a private e-mail that I reason to suspect that they may be
superior to my CP caps.

I did blow about 6 caps, but this was because they were left over from a
VTTC and were not assembled for proper disruptive duty. Interestingly, only
outer caps blew, but I think I read about a non-linear voltage distribution
phenomenon somewhere.

Of course, for large MMCs of relatively high value and voltage, the total
cap mass becomes substantial, so the teeny weeny remark was just a bit of
silly Coiling humor. So....no need to convince me, and I am glad that the
miserable rolled poly caps are now obsolete, as are Salt water caps (unless
one is $$ strapped). Though I did make some HDPE SW caps that performed very
well, as I've recounted here before.

When I make some MMCs, which will have to be soon unless I make a 120 bps
RSRG to save my CP caps--if they're not already fatally compromised--I will
definitely consult your site, which I've been to many times. It was good to
hear that Finn Hammer's failure was due to resistor problems and not the
caps.

Finally, regarding CP caps. I must tell you that I am a bit frosted about
those very expensive toys: 300 clams a pop. It was not until recently that I
learned that they were bps limited by a CP engineer. At the time (1999?),
however, they were the thing to have and I did not know enough to specify
break rate. I was simply tired of blowing SW cap  HDPE dialectrics--deli
buckets.  Of course, higher bps rating probably would have been
prohibitively expensive.

I have heard of those failing catastrophically, to say the least. Oh well,
they are very impressive in appearance.
Dave




Original poster: "Terry Fritz" <twftesla-at-qwest-dot-net>

Hi Dave,

Chip's blowing his CP caps all over his roof in 1998 on Halloween night
started MMC caps...  I think yours are like his.  Poor contact between the
"packs" inside the cap.  They can't take high RMS currents without
literally exploding!  I saw Chip's caps and the plastic cases blew apart,
dramatically!!  I think Chip described it as a big "explosion on his roof".
 He pulled that cap off and put on the other one and then noted 'another'
big explosion on his roof...

RMS current is directly proportional to the BPS rate.  Chip's coil can run
like 1000+BPS...  At the time, the "key" to streamer power was to run very
high BPS rates.  However, that puts a terrible strain on the caps.  Don't
run your CP caps at high BPS rates.  They really will die!!!!!

Chip made an early MMC cap to replace his CP caps that ran the next
Halloween, just fine ;-))

The trick to MMC caps is that we were able to calculate the primary peak
and RMS currents and design the MMC to match the situation.  We knew
exactly what we were dealing with and it simply "had" to work.  MMC caps
are pretty high tech!!  They may look like just big dumb caps, but we are
talking like 2kV, 0.0002 dissipation factor, 1000 amps peak 15 Amps RMS,...
each!!  They even self heal with an over voltage...  Like a million
times!!!  Remember that o'l 90 mil poly... MMC caps hold off the same
voltage at 2 mil...  Of course, the "poly" in MMC caps is water clear and
one of the most pure plastics on the planet...  That's why they cost so
much at like $3.00 each  ;-))

Since MMCs have become mainstream, homemade rolled poly caps have instantly
become extinct.  Commercial caps are still favored buy the pros that can
spend a lot of cash on over designed caps.  But MMCs can bet those easily
IMHO.  I have tested MMCs that were literally on fire that worked just fine
;-))  I can hold an MMC in may hand that can do better than any rolled
cap...

Rest assured that MMCs are a big deal!!  IMHO, they are the 'only' deal
these days...

Cheers,

	Terry



At 10:08 PM 9/5/2002 -0400, you wrote:
>John,
>Did the breakrate sound high? This is a very interesting question. I can't
>say that I've ever listened specifically for this parameter, though I
surely
>will in the future. I listen for general tune, of which breakrate is
>obviously a part---I can't really describe what I listen for. I know it
when
>I hear it.
>
>Reviewing my aural memory banks: I did note that with NST power, the
>breakrate sounded quite low. This changed some with gap width and power
>level. Moving to Piglet power--scanning memory banks--the report from the
>discharge was so incredibly loud that I'm not sure what was going on. I'm
>sure this can be measured with a scope, but I've not endeavored to master
>those scoping techniques.
>
>One thing's for sure: I had forgotten the daunting sense of power exuded by
>coils at higher powers. The scouring, screaming note. I lift the hearing
>protectors on occasion just to increase the intimacy. And the appearance of
>the discharge. One truly gets a feel that extremely high voltages are being
>produced. This is not the case at lower power levels.
>
>The aesthetics of coiling. We really should examine it with greater depth.
>"What Coiling Means to Me"....
>
>Yes, I've been hoping that series operation  of these caps would insert
more
>safety factor. To use them in a system other than that whose gap is a 120
>BPS SRSG is Probably foolish, though it's hard to see how those teeny weeny
>(relatively) little MMC caps are able to withstand the punishment, though
>they obviously do.
>Dave
>