Re: Cap Pulse Ratings
From: Edward J. Wingate[SMTP:ewing7-at-frontiernet-dot-net]
Reply To: ewing7-at-frontiernet-dot-net
Sent: Monday, September 08, 1997 11:09 PM
To: Tesla List
Subject: Re: Cap Pulse Ratings
Tesla List wrote:
> From: Malcolm Watts[SMTP:MALCOLM-at-directorate.wnp.ac.nz]
> Sent: Sunday, September 07, 1997 3:38 PM
> To: tesla-at-pupman-dot-com
> Subject: Cap Pulse Ratings
> Hi all,
> This one's directed to anybody _other_ than those who were in
> the group purchase of Condenser Products capacitors (e.g. Ed
> Wingate). I am curious to know - what is the PPS rating on your caps?
> The ones we scored in the group purchase were rated at 120PPS
> (American mains, resonant charge, static gap).
The last 2 caps I ordered from Condenser Products were custom designed
for my needs and were rated .15 mfd -at- 22900 VACRMS, 60 HZ, 120 pps,
100khz-500khz ringing freq. These caps (TC154-38-250) were $950.00 each
and are 8 5/8" in diameter and 26 1/2 " long. I use these in series on
my twin coil for a total tank capacitance of .075 mfd. I use a
synchronous rotary gap on this system with a break rate of 120 bps, 3600
rpm and two 1/2" tungsten studs on the rotor. With a total series
voltage rating of 45,800 VAC (with only a max of 22,900 VAC input) ,a
120 bps break rate and a resonant frequency of approximately 70 khz
these caps should last longer than I will. ;^)
I have dealt with Condenser Products for years and I am convinced that
the engineer at CP designed these caps more robustly that the nameplate
ratings imply. For comparison, I also have a few CP TC104-25-225 .1 mfd
-at- 15,000 VACRMS, 60 hz, 120 pps, 100 khz-500 khz ringing freq. The .15's
have almost 3 1/2 times the volume of the smaller .1's which seems
disproportionate in light of the ratings of each.
I have been using two of the CP .1's in the Tesla equidrive
configuration on my magnifier for over two years at a break rate of
between 700 and 800 bps and an input voltage of 14.4 kv -at- approx. 750
ma. These caps are both over 5 years old and were used in previous
systems and now have a total of over 15 hours of continuous run time on
the magnifier alone and they just keep hummin' along.
High energy pulse caps WILL fail sooner or later, period. Which one it
is depends on how close to the ratings they are run. The engineer at CP
told me that they rate their caps in number of shots until failure,
figured from voltage ratings, frequency, pps, etc. If you raise the
voltage rating while maintaining the same input voltage, freq. and pps
the shot life increases. If the input voltage, pps or the freq. goes up
the shot life decreases. The ratings are all interdependant on each
other. I have, in the past, even ordered caps from CP with extra
sections added to increase the voltage rating, which also increases the
shot life. Of course, a spike or overvoltage condition across a cap with
no safety gap can take it out in a heartbeat.
I know this is probably way more information than you wanted, but I am
just trying to make the point that I have had good luck with CP caps.
Always in favor of lasting components.