Re: Air insulation

To: tesla-at-pupman-dot-com
Subject: Re: Air insulation
From: Richard Hull <hullr-at-whitlock-dot-com>
Date: Fri, 18 Oct 1996 10:57:07 -0700
Tesla List wrote:
> 
> > Subject: Air insulation
> > Subject: Air insulation
> 
> >From huffman-at-fnal.govThu Oct 17 21:55:35 1996
> Date: Thu, 17 Oct 1996 09:54:10 -0500
> From: huffman <huffman-at-fnal.gov>
> To: tesla-at-pupman-dot-com
> Subject: Re: Air insulation
> 
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> 
> Hi Richard and All,
> With the discussions about insulators (oil fill and such) I was going to
> mention that adding a dielectric does not always reduce the arcing when
> high voltage is present. I had an overcoupled coil that I tried to
> 'insulate' the primary from the secondary with a roll of polypropylene. It
> seemed to make the situation worse. I did this back before joining this
> discussion and know little about the nature of what was going on. It
> appears that the electric field will concentrate in materials with higher
> dielectric constants (K). Like adding magnetic materials to increase
> magnetic coupling, dielectrics add to electric coupling or concentration.
>
> Dave
> ----------Richard Hull wrote:

> > The really neat thing about air is it has a dielectric constant of about
> > 1 (unity) or virually equivalent to the vacuum lof outerspace!!  This is
> > nice and is airs one great saving grace as an insulator.
> >
> > In the study of dielectrics, high voltage, and the like, it is quickly
> > realized that some of the best solid insulators have rather higher
> > dielectric constants than air. (k= 2-6).  It is also quickly learned that
> 
> > with a given field voltage, the field intensity grows to horrendous
> > levels at the interfaces of dielectrics of varying dielectric constant.
> > Have you ever seen sparks crawl along a sheet of mylar in air?  I have!
> > the contact of two dielectrics of differing values is a collection point
> > for intense fields!
> >
> > The lower the dielectic constant the less the field gradient becomes for
> > a given voltage.  Thus, avoid close quartered high differential
> > dielectric constant materials and you won't see sparks seeming to prefer
> > to zip along this corridor, rather than leap out into air.  Why should
> > they?!  They are happy staying where the fields are intense.  Therefore,
> > the best way to use air insulation is to allow for large radius of
> > curavature metallic charged surfaces to contact air directly without
> > other insulation.
> >
> > Richard Hull, TCBOR

Dave,

I thought that what I was saying above!!  the application of solid 
dielectrics for insulation often worsens a bad situation!

Richard Hull, TCBOR