Re: Dielectric constant table

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

Original poster: "Crow Leader" <tesla-at-lists.symmetric-dot-net> 

----- Original Message -----
From: "Tesla list" <tesla-at-pupman-dot-com>
To: <tesla-at-pupman-dot-com>
Sent: Thursday, September 18, 2003 6:23 PM
Subject: Dielectric constant table


 > Original poster: The MCP <ejkeever-at-comcast-dot-net>
 >
 > I'm wondering how long it's been since the dielectric tables present on
many
 > tesla coil sites have been updated.
 >
 > I'm also wondering about some of the values on them. For example, the
table
 > says that Mylar is good for 7.5Kv *per mil*. However, one of my early

It's not a linear correlation. 2 mils is not twice the strenght of 1 mil.
Also, with plastics, there are different grades. Impurities or holes in film
will botch up the dielectric strenght, and since they're always there, you
may need to compensate with many layers.

 > attempts at a cap using 10 mils of mylar failed at 5000V rms. Something is
 > wrong.

5kVAC across a single layer of dielectric is what's wrong. It doesn't work
in practice. You need either several lower voltage cap sections in series,
or multiple layers of thin dielectric wound together. 5kVAC is very
destructive becasuse of the corona.

If you want EZ to make high voltage DC cap, use the plastic from those page
protectors with the black paper inside, and the holes for a three ring
binder and aluminum foil. The plastic might be polystytene. It will leak
like mad, but a single layer can take 20-30kV and give you a nice spark when
you discharge it. This works way better than saran wrap or acetate overhad
projector sheets.

KEN