LOSS FACTORS??

To: "'Tesla List'" <tesla-at-pupman-dot-com>
Subject: LOSS FACTORS??
From: Tesla List <tesla-at-stic-dot-net>
Date: Mon, 2 Feb 1998 23:02:58 -0600
Approved: tesla-at-stic-dot-net

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From:  Bert Hickman [SMTP:bert.hickman-at-aquila-dot-com]
Sent:  Sunday, February 01, 1998 8:44 PM
To:  Tesla List
Subject:  Re: LOSS FACTORS??

Tesla List wrote:
> 
> ----------
> From:  Zuma [SMTP:mwise-at-ns.sosis-dot-com]
> Sent:  Saturday, January 31, 1998 10:45 PM
> To:  tesla-at-pupman-dot-com
> Subject:  LOSS FACTORS??
> 
> Could someone please tell me where the loss factors for di-electrics
> come from. How are these figures derived? Are they based density, what?
> I would like to know for the specific reason so I can make sense of all
> of this talk of high loss or low loss for different caps!
> 
> Chris

Chris,

The loss factors are determined experimentally, and ultimately are a
property of the molecular/ionic structure and purity of the dielectric
material itself. Tables of dielectric constants and dielectric losses
are often provided for low frequency (50 or 60 Hz) and at higher
frequencies (low frequency RF through microwave). However, there's no
direct way for you to relate appearance, color, density, or any other
macroscopic property to the dielectric loss. And there's no way to make
"sense" out of dielectric constants and losses without delving
significantly deeper into the physics and behavior of dielectrics. 

However, you can use tables of dielectric properties that are found in
books such as the "CRC Handbook of Chemistry and Physics", or
specialized books such as "Dielectric Materials and Applications" by Von
Hippel, or "Engineering Dielectrics Vol IIA" by Bartnikas. The latter
references also cover theory and testing of dielectrics, and are
available from any moderately sized technical library.

However, I can also save you some time and research - For Tesla Coils,
the best performing, reliable, practical, lowest cost, and easiest to
use dielectrics for home-made caps are:
   1. low-density polyethylene OR
   2. polypropylene
Any other commonly available dielectric you're likely to encounter will
cost more, and perform poorer. This includes glass, PMMA (plexiglass),
PC (Lexan polycarbonate), PVC/Vinyl sheeting, and PET (Mylar). While
polystyrene is also a very low loss dielectric, it unfortunately has
lousy solvent characteristics and is brittle. Teflon is low loss, but is
also porous and VERY expensive. Ruby mica can be pretty good, but is
virtually unavailable. Fortunately, polyethylene sheet and film are
readily available, and best of all, they're CHEAP!

Today's commercial pulse caps use specially prepared/processed
polypropylene as the dielectric, combined with kraft paper and
high-dielectric constant oil. The next best thing _you_ can use is
polyethylene and mineral oil! There's virtually no way to avoid running
in oil to suppress corona. But this would be true for virtually ANY
dielectric you choose to use other than a vacuum. 

Safe cappin' to you, Chris!

-- Bert --