RE: Commercial Caps for Tesla Applications

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

Hi All,

	I looked at one of Chip's blown caps.  The interconnection between the
individual "packs" was weak.  There was arcing due to casual contact and
such.  A very easy thing to fix but they did not realize the current needed
or someone made a mistake somewhere...

All custom capacitor places have problems now and then so this manufacturer
is probably no worse or better than any other.  Too bad things turned out
sort of bad in this case :-(

One thing that is rarely mentioned and may be sort of new is that we should
NEVER connect a safety gap directly across a capacitor.  The sudden direct
shorting of a fully charged cap can draw enormous current and damage any
large cap.  A small resistor, air choke, or having the primary in the loop
limits the current to a safe value.  In this case, shorting these already
weak caps may be especially bad for them.

Although we usually don't think of MMCs for really large caps, a large
value MMC made from large snubbers would probably be cost effective and
very robust.  You would not need too many and they can be bolted up nicely
and professionally.  Snubbers caps have the same voltage overload and self
healing as other caps despite their large value and stored energy.  They
would actually be far more immune to shorting too since they can stand full
power shorts better do to the current being distributed over many strings.
They would have all the advantages of no oil, reparable, selectable values,
etc...

Cheers,

	Terry


At 01:43 PM 8/16/00 -0600, you wrote:
>There was actually more to the problem than just that.  Some of the caps
>were defective in the first place and blew up.  Apparently they were willing
>to work with the people who had the problems until one or two people started
>threatening them with legal action and being rather unpleasant.  This was
>probably the genesis of their policy.
>
>Personally, I wasn't too awfully impressed with the quality of the caps.  I
>had two blow up (loud, like 1/2 an M-80).  I wasn't running them too hard I
>thought.  I was running them about 500bps at 14,400 volts.  I was under the
>impression that the TC caps were designed for Tesla Coil service and that
>they were therefore capable of handling the resulting resonant rise, etc.
>If I remember correctly, I even had a safety gap across them.  Oh, the other
>thing is that they were cylindrical and thus resistant to a fair amount of
>pressure.  There was no air space in them, so when they blew, they really
>blew.  The home made rolled cap that I toasted had a bunch of air space at
>the top, and when it went, it was just quiet gurgling.
>
>Chip
>
>-----Original Message-----
>From: Tesla list [mailto:tesla-at-pupman-dot-com]
>Sent: Wednesday, August 16, 2000 1:13 PM
>To: tesla-at-pupman-dot-com
>Subject: Re: Commercial Caps for Tesla Applications
>
>
>Original poster: FutureT-at-aol-dot-com 
>
>In a message dated 8/16/00 11:18:26 AM Pacific Daylight Time, 
>tesla-at-pupman-dot-com writes:
>
>> By the way I live about
>>  10-12 miles from Condensor Products Corp.  Unless your a buisness or can
>>  convince them that you know what you are doing they will not sell Tesla
>>  Caps. to private individuals. I have been reviewing some of the old
>>  Tesla List Archives and from what I have read they did sell to private
>>  individuals at one time. I have been messing around with high voltage
>>  for 13 years Im still here and they told me "NO".
>>  Best Regards Jeff KD4LYH 
>
>Jeff,
>
>Yes, Condenser products sold to individuals until some of the buyers
>of their caps overvolted them (unknowingly), and blew them up and
>then blamed Condenser products.  
>
>Cheers,
>John Freau
>
>