Re: Capacitor design and Toroids

Dave Huffman wrote:

Has any one used Kapton for the dielectric of a capacitor?
This stuff seems incredible with specs like..
dielectric strength of 7000V/mil
dielectric constant of 3.5
and dissipation factor of 0.003 at 1KHz?

Two things:

The 7000V/mil is almost certainly the strength for thin
films. IF you make the Kapton 60mils thick, then the 
strength will certainly be less. My references show that
Kapton (trade name for polyimide PI) has only 1.5 times the
breakdown strength of polyethylene for equal thicknesses.

Also, a dissipation factor of .003 for PI sounds right. 
One of my tables shows:

DF=.002 at 50Hz and .005 at 1Mhz

Another table for Phelps Dogde  PI(aromatic) coated wire shows:

DF=.0009 at 1kHz, .006 at 100kHz, and .009 at 1Mhz

-Ed Harris