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Re: PET ( or MYLAR )
Date: Wed, 26 Aug 1998 18:48:19 -0700
From: Jim Lux <James.P.Lux-at-jpl.nasa.gov>
Tesla List wrote:
>
> Well, if 6u PET holds 600v then 9 mil PET should hold 900 kV, no?
No... thin layers have higher dielectric strength (per unit thickness)
than thick layers. A phenomenon that has surprised many. Ruby mica has
such a high dielectric strength partly because it is composed of many
very uniform very thin layers stuck together.
I should
> be able to get a pop bottle to stand up to a 15 kV Tesla coil, even with 15
> kV of LF riding ont he 15 kV of 60 Hz. I notice the CRC handbook lists the
> dielectric constant of PET the same value for all three frequencies in their
> table. Thats gotta be a good sign for low dissipation. I dont have a
> microwave oven for dielectric loss testing right now.
A microwave oven is 2450 MHz, many, many decades above the 100 kHz or so
for a TC. Loss at microwave frequencies may not be all that well
correlated with loss at low frequencies. And, the change (or lack of
change) in epsilon (the dielectric constant) doesn't have much to do
with the change in loss factor. There are a number of substances with
dielectric constants that are relatively constant over frequency (around
2.5) that have remarkably high losses at some frequencies.