RE: Di-electric Disaster

To: tesla-at-pupman-dot-com
Subject: RE: Di-electric Disaster
From: "Lau, Gary" <Gary.Lau-at-compaq-dot-com> (by way of Terry Fritz <twftesla-at-uswest-dot-net>)
Date: Mon, 15 May 2000 21:17:36 -0600
Approved: twftesla-at-uswest-dot-net
Delivered-To: fixup-tesla-at-pupman-dot-com-at-fixme

The dielectric dissipation of oil is irrelevant in a plastic dielectric
capacitor.  It's the plastic's dissipation that matters, as that's 99.99% of
the stuff between the plates.

The breakdown voltage of the oil is not really that critical either.  The
oil's main function is just to displace air.  The types of failures in home
made poly/oil caps are typically:
1)	Dielectric punctures due to either too thin poly or localized
heating dor to partial discharge within the poly, or
2)	An arc surface-tracking across the surface of the poly.
In neither case would a super insulating oil have helped.

I don't have the tables here in front of me but I think I recall seeing that
PE has a slightly better dissipation factor than PP.  But there must be a
reason that commercial caps use PP exclusively in HV pulse discharge
applications, perhaps it has a higher melting point.

The perfect loss-less dielectric would be a perfect vacuum, but that's
cumbersome to deal with.

Regards, Gary Lau
Waltham, MA USA

-----Original Message-----
		From:	Tesla List [mailto:tesla-at-pupman-dot-com]
		Sent:	Monday, May 15, 2000 7:36 PM
		To:	tesla-at-pupman-dot-com
		Subject:	Di-electric Disaster

		Original Poster: "Dan Kunkel" <kunk77-at-juno-dot-com> 

		Just curious about di-electrics in capacitors...

		mineral oil vs polyehtylene...which is better in terms of RF
dissipation
		losses? also what is the breakdown voltage of mineral oil?

		polyehtylene vs polypropylene...does polyprop. have less RF
losses?

		Is there a truly "lossless" di-electric?

		Dan