Re: Paper/Oil Capacitors

[Terry Fritz <twftesla-at-uswest-dot-net>]

Hi Ed,

At 06:12 PM 8/19/00 -0400, you wrote:
>Tesla list wrote:
>> 
>> Original poster: Terry Fritz <twftesla-at-uswest-dot-net>
>> 
>> Hi Greg,
>> 
>>         Two years ago, 1/4 of the posts on this list delt with oil/poly 
>caps.  In
>> only a year, MMCs have virtually obsoleted homemade oil caps (I am waiting
>> for them to obsolete the commercial ones too!).
>> 
>>         Rather than list the problems with paper and oil caps, I'll just 
>say that
>> MMC caps are better, cheaper, faster, more reliabile, adjustable, don't
>> drift, exact value, don't leak, don't explode......  A number of people who
>> were in the middle of making oil caps stopped in the middle of making them
>> and went to MMCs.  They really are that much better.
>> 
>> http://users.better-dot-org/tfritz/site/MMCinfo/MMC.html
>> 
>> Cheers,
>> 
>>         Terry
>
>Hi Terry,
>
>That's a pretty strong statement.
>
>I think you will have a long wait for MMCs to obsolete commercial pulse
>caps, or have you built quite a few small and large coils using both MMC
>and commercial pulse caps? I just wondered what comparisons your
>statement was based on. I don't expect to see Maxwell, PCI, CP, et all
>offering MMCs any time in the near future!
>
>Best Regards,
>
>Ed Wingate RATCB

I don't expect them too either ;-)  Those companies do not have the basic
technologies and mass production capability needed to make large quantities
of high reliability film caps (although they could go out and buy it... but
they could not compete effectively with the already established companies).
 They "should" have the in house testing and engineering but it is not
presently nearly as advanced as other manufacturers.  The sources you list
are more geared toward limited production and highly custom (expensive!)
applications.  They do presently own the multi-kilo-joule discharge markets
which will continue...  

Film polypropylene caps for high voltage/high AC current applications is a
big and fast growing business.  A number of older type caps are being
phased out since their equivalents can be made better and cheaper in poly
film.  Combining smaller mass manufactured poly film cores into larger
single offerings is a very cheap and effective way to come up with reliable
values that a single poly cap cannot presently offer (they have more tricks
however :-)).  One can buy individual caps and make a say 400nF 20kV MMC
for maybe $400.  However, if the equivalent was manufactured from the start
and combined into that value in a single package the cost would be vastly
reduced.  Maybe <$100 at OEM.  So, if the demand shows itself, A number of
manufactures are more than capable of very quickly offering such devices.  

The same reasons we have all flown to MMCs will drive similar commercial
HF/AC applications to arrayed poly film caps too.  Many places now use
large poly film arrays, but as individual components.  The advantage of
having them all in one OEM package is obvious...

One similar change was from vacuum high voltage/frequency capacitors to the
newer power ceramics.  1/10th the cost, 1/100th the size, vastly higher
reliability...  Even the vacuum variables are being phased out now in a
number of applications...

The technologies in capacitors are changing radically these days.  Don't
expect things to stay the same...  Which is really great because the new
stuff is really wonderful and the technologies will spin down to us.  Or...
ours will spin down to them :-))

Of course, the truth will be know as we sit back and watch what unfolds...

Cheers,

	Terry