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Brudh Discharge [Cap W/ Electret]
Original poster: "davep by way of Terry Fritz <twftesla-at-uswest-dot-net>" <davep-at-quik-dot-com>
Tesla list wrote:
> Original poster: "by way of Terry Fritz <twftesla-at-uswest-dot-net>"
> Point well taken. A pre-stressed dielectric would only be stronger if
> reversed biased.
> The purpose of an electret cap is two fold. While an electret does
> not provide free energy, it does act as a battery and can provide the
> illusion of free energy.
One suspects that applying AC to an electret would:
waste energy as the applied AC shakes up the
'frozen in' field.
Tend to 'scrub' the frozen in field.
> (An electret should be shorted to maintain its charge, somewhat analogous
> to a keeper on a magnet.) I also have been curious, if a brush discharge
> were biased, would there be an observable difference?
There are certainly documented differences in the appearance
of positive & negative brushes, with DC excitation. What the
effect with AC superimposed on DC is hard to say...
> Would a static build-up effect the discharge?
Presumably depends on the relative magnitude of each.
Also, the commonly reported 'shock form the depowered
secondary (form?) effect is commonly attributed to an
electret effect in the dielectric of the coil form.
There is an effect called (roughly) glow discharge rectification
that can leave a low amplitude (say 10-15kV DC as a Tesla secondary
is powered down... Of course the usual cap is in the primary...
> -mike day
> > -----Original Message-----
> > From: tesla-at-pupman-dot-com [SMTP:tesla-at-pupman-dot-com]
> > Sent: Monday, May 07, 2001 2:58 PM
> > To: tesla-at-pupman-dot-com
> > Subject: RE: Cap W/ Electret
> > Original poster: "Lau, Gary by way of Terry Fritz <twftesla-at-uswest-dot-net>"
> > <Gary.Lau-at-compaq-dot-com>
> > I see a couple of problems.
> > First, polycarbonate and acrylic are fairly lossy dielectrics compared
> > to polyethylene or polypropylene.
> > More importantly, by "freezing" a static charge into the dielectric, it
> > would then have a DC bias. If an unmodified sheet of the material had a
> > nominal static breakdown voltage rating of 10kV and you imparted a 5kV
> > bias into it, then it could only withstand a 5kV AC oscillation, whereas
> > an unmodified sheet could withstand 10kV..
> > I'm not sure what the goal of the electret is in this application.
> > You're not going to be getting any "free energy".
> > Gary Lau
> > MA, USA