Re: failed cap

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

Original poster: "Gerry Reynolds" <gerryreynolds-at-earthlink-dot-net> 

Has anyone tried to use two or three layers of thinner PE dialectric between
plates to allow statistics (of having the defects of those multilayer sheets
line up at a common point) to improve the reliability of the home made cap.

Gerry R
Ft Collins, CO

 > Original poster: "Dr. Resonance" <resonance-at-jvlnet-dot-com>
 >
 >
 > Any home brew caps using a relatively thick dielectric (64 mil) is subject
 > to this type of failure.  You had some small voids in the dielectric.
 > Inside these voids the dielectric constant is different from the
surrounding
 > material.  The result is corona inside the small void.  Corona produces
heat
 > and eventual failure occurs.  Some of these voids are so small they almost
 > can not be seen with the human eye.  As the corona forms immediately,
 > breakdown begins.  It's a slow process but eventually the void produces
 > dielectric failure as you have experienced.
 >
 > Professional manufacturers always use 0.5 (1/2) mil thick dielectric
 > material to avoid this problem.  This dielectric material is so thin it
can
 > only be handled by expensive winding machines and can not be touched by
 > human hands.  The entire surface area of this dielectric material is
checked
 > for voids prior to acceptance by the cap mfgr.
 >
 > I toured Maxwell Capacitors years ago and they use a "clean room" for all
 > their special energy discharge cap winding processes.  Some of their other
 > processes such as soldering extended endfoils together were equally
 > interesting.
 >
 > Stick with the MMC caps and a 2.5:1 ratio (DC to AC) and you will have
 > virtually no trouble in the future.
 >
 > Dr. Resonance
 >
 > Resonance Research Corporation
 > E11870 Shadylane Rd.
 > Baraboo   WI   53913
 >  >
 >  > Hi.
 >  >     i built a cap with 1.6 mm or 64 mil thick PE dielectric and put the
 >  > whole thing in canola oil. It worked great for a while but while i had
 > just
 >  > the cap across the nst ,,, with no tesla coil connected.. to test my
new
 >  > mulitgap sparkgap... the PE between 2 of the plates broke down and now
it
 >  > blows bubbles and hisses and only produces a spark in the gap if the
gap
 > is
 >  > 1 mm or 30 mil . Its pretty much had it and must be breaking down at 1
or
 > 2
 >  > thousand volts..IS it more stressfull on a cap with no tesla coil
 > connected
 >  > and is it suprising my cap did not last in my config. The plates are
1.75"
 >  > clearance from each end and 1" along the sides. !6 sheets of makes each
 > layer
 >  >
 >  > Phil
 >
 >