Re: Hot spot

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

Original poster: "Sean Taylor by way of Terry Fritz <teslalist-at-qwest-dot-net>" <taylorss-at-rose-hulman.edu>

An easier way to get rid of bubbles from drying epoxy is by using a heat gun
. . . the air expands and the bubbles pop.  Just don't stay in one place too
long with the heat gun, and hopefully you're already turning the drying form
slowly, while it's horizontal.

Sean Taylor


 > Original poster: "Resonance Research Corp. by way of Terry Fritz
<teslalist-at-qwest-dot-net>" <resonance-at-jvlnet-dot-com>
 >
 > A common problem in epoxy HV transformer design and construction.  There
 > probably was an air bubble in the drying epoxy.  The air bubble has a
 > different dielectric constant than the surrounding dielectric material.
As
 > the unit runs small sparks occur on the interior surface of the bubble.
 > This causes intense local heating which eventually can lead to hot spots
or
 > final dielectric breakdown.
 >
 > Commercial xmfr mfgrs overcome this by using vacuum epoxification
 > techniques.  The windings are shorted out and heated with a primary
current
 > while the epoxy cures which drives out the air bubbles and the vacuum
sucks
 > them away.