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CAPACITOR QUESTIONS !?!



Talking about capcitors and dielectrics:

 >The rating depends on the film thickness, cleanliness, and
 >quality of construction. If you are using 60 mil LDPE under oil
 >and everything is spotless you can get a reliable cap that will
 >hold up with 9-10KVAC inputs into a spark excited tank circuit.
 >Thinner films will hold up to proportionally higher voltages
 >(I know this sounds backwards, but it is quite true), but a     
 >tiny flaw, speck, or air bubble will cause failure, and thinner
 >dielectrics are more difficult to work with. Capacitor types,
 >construction, and characteristics are constantly discussed      
 >here: keep you ears open. 

Quoting Chris Cudahy <ccudahy-at-calumet.yorku.ca>:

> That really does sound backwards to how I though dilerectric 
> strength worked - Could you explain this in more detail ?

I have changed the topic of this reply, because it has the
potential to seed a new thread: CAPACITOR QUESTIONS !?!

I am not a materials scientist, but there are others with far
more knowledge on this subject out there that could expound on
this topic. Guys?

> BTW, as long as were talking about LDPE, is there much of a
> difference (for cap use) between LDPE and HDPE ? Are their 
> properties about the same ?

In general Tesla coil applications you will find the LDPE to be
much more versitile and useful than HDPE. A good example: in
capacitor applications where any bend or curve of the dielectric
is required HDPE will "craze" with microfractures if it is
stressed excessively. These stress cracks cause premature failure
of the dielectric = don't use it in rolled caps where the rolled
design gives x2 the value per given plate area.

Richard Quick


... If all else fails... Throw another megavolt across it!
___ Blue Wave/QWK v2.12