Mixed dielectrics

To: mail11: ;
Subject: Mixed dielectrics
From: pierson-at-msd26.enet.dec-dot-com
Date: Sun, 20 Oct 96 10:50:32 EDT
Cc: pierson-at-msd26.enet.dec-dot-com

>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).
	Yup.  As Richard Hull pointed out (and as was learnt ca 1910 in
	the electric power industry, adding dielectrics (solid or otherwise)
	is not just a matter of adding up the volts/mil (especially of
	mixed stacks (ie: trying to use a physically stong material to
	reenforce an electrically strong one).  Unless the dielectric
	constants (and for ac work, the capacitances) of the layers are
	taken into account, exceeding odd (and destructive) effects can take
	place.

	(Has anyone every reprinted Dielectric Phenomenon in HV Engineering
	by Peek?  He goes into this in detail, ca 1915, for all manner of
	substances (ok.  NO PLASTICS  8)>>), frequencies, humidities
	gap shapes....  Or is their a more current reference?)

	regards
	dwp