FW: Singing them ol' capacitor blues
From: Bert Hickman[SMTP:bert.hickman-at-aquila-dot-com]
Sent: Wednesday, June 18, 1997 9:26 AM
To: Tesla List
Subject: Re: Singing them ol' capacitor blues
Tesla List wrote:
> From: Larry Robertson[SMTP:LWRobertson-at-msn-dot-com]
> Sent: Wednesday, June 18, 1997 1:46 AM
> To: Tesla Builders
> Subject: Singing them ol' capacitor blues
> Hey ... long time no write - been struggling with capacitor manufacture.
> BTW I phoned Condenser Products for a quote on a 0.025/20kV cap.,
> the price went up to $340, so I decided another round would't hurt.
> I've been so careful with this one, and spent so much time bringing
> it up I named it "Baby".
When I was constructing my flat plate caps, I called them lots of
names, none of them close to "baby" tho...
> This time I used 3 sheets of .030 polypropylene as dielectric, 24
> inches wide, and 20 inch AL flashing as the plates. I found an
> arrangement that caused the plates to extrude on the outside
> of the roll separated from the poly, and 90 degrees from each other.
> I used a friction connection with 1 inch strips of the same flashing
> all the way up as the leads, all well taped down. Man, is that
> tough to roll up tight enough to fit in a 6" pipe.
> Measured on a Fluke 87 at .018.
> Then I took my pail of mineral oil and the sealed capacitor to
> work and applied a vacuum pump for about 45 minutes. The top
> plate bowed in by about 1/4 inch, but held. I guess I'll use thicker
> Plexiglas on the next one - this was 1/4 " thick, 6 inches in
> diameter, and the air pressure at 15 PSI atmospheric could have
> been as high as 400 lb..
> The mineral oil foamed furiously when admitted, and continued to boil
> for the next hour. I backfilled four times with dry nitrogen gas.
> Although the outgassing slowed, it was still at a medium boil after
> an hour and a half, so I thought I was either pulling off lighter
> fractions of the oil or sucking air through the PVC container
> so I vented it with N2 and held it gingerly all the way home.
> On a pumped capacitor, I don't understand what breaking it in
> will do, but I did it anyway. In fact Sargeant mentions breaking
> in commercial capacitors, so something must transpire.
> ( And by the way - which one of you toads got that pristine
> copy of "High Power Electronics" from Justin's Books last
> week while I was out of town doing honest work. I phoned the
> store and they said seven people called the same day it was
> offered.Finally went for $112.)
Smile when you say toad!! :^). And it wasn't quite as high as $112...
The original offering price was only $45.00 - this changed quickly when
Julian got all the early-morning calls! This book apparently must have
been stashed away in some nook and cranny in a warehouse, since it
didn't look like it was ever even openned, and doesn't have a mark on
it. It came complete with the original dustjacket as well. I just
happenned to catch the ad at 5:30AM on Bibliofind and was immediatly on
the horn and sending e-mail to Julian. There were three books that I'd
pay anything like this for... now there are two. Better luck next time!
BTW, I also asked Tom Lindsay of Lindsay's Books if he would consider
making a reprint of this book. If enough coilers ask him the same
question, he might be willing to consider it! He was not familiar with
the book. Also, Barry Benson has indicated in a private communication
that the exact text of HPE is also contained in an Air Force training
course on Pulsed Power. This means that it MIGHT be available via the
Government Printing Office...
> Another by the way : pursuant to my last short post, a
> schematic of a solid state pulse generator is on a Russian
> site : www.dux.ru/guest/exci/power.html .
Alas, the site must only be availble during certain hours - when I tried
accessing it, all I got was an hourglass on Netscape! :^(
> So I'm running Baby at about 18" of spark for a day or so. It
> is a very quiet capacitor, even at 10 kV straight across the
> transformer it doesn't make any corona noises at all. The
> spark gap noise is different too. My first cap. had the plate edges
> sticking out and shorted turn for turn on each end and had huge
> 5 Mhz parasitic oscillations as observed on a 'scope nearby.
> Although I find it hard to believe those would be aurally detectable,
> something about the spark seemed snappier. Seems to be
> performing similarly though.
Sounds like you've got a winner, Larry! With 90 mils of triple-poly,
"baby" ought to run forever at 10 KVRMS!
> This time I tried a safety gap across Baby, at least initially.
> When that goes off it is ten times louder than either the main
> gap or the tesla discharge. A ball of green plasma surrounds
> the copper gap, and inspection reveals all oxide blown
> clean off for about 1/4 inch.
"Sounds" like you may want to put some small RFC's in series with the HV
> Ain't coilin' wonderful!
> Not enough power in ...
> Morgan Hill, CA
BTW, I ran into a guy at a Hamfest two weeks ago who was selling rolls
of LDPE film that was originally used for heat shrink/blister-wrapping.
Each roll was 20 inches wide, and the material was 8 mils thick. The
rolls weighed about 68 pounds apiece (works out to be about 1000 linear
feet/roll). These sound like they'd make nice capacitor dielectric -
he's willing to sell these for $15-$20 a roll. It looks like it would
make gangbuster dielectric material for either flat or rolled caps. 8
mil poly is not all that common, and certainly not at this price! Anyone
in the Chicago, IL area interested?
Safe coillin' to you!
-- Bert --