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RE: [TCML] Capacitor encapsulent
No, I don't know what it is for HDPE. But it's important to understand that when building a reliable cap, it's incorrect to think that choosing a dielectric thickness based on X kv/mil and Y peak voltage required means you need Z thickness. I think there is a non-linear breakdown voltage vs thickness relationship. But more importantly is something called the corona inception voltage, which means that corona will occur if the applied voltage is more than something like 650V, regardless of dielectric thickness. As soon as corona forms with a plastic dielectric, the dielectric degrades rapidly. The CDE caps we use in MMC's are actually constructed as two seriesed caps, with a "floating plate" between the two terminals, to effectively double the corona inception point.
So, unless you build your DIY cap as several seriesed units, you will get corona and a compromised life expectancy, regardless of dielectric thickness.
Regards, Gary Lau
MA, USA
> -----Original Message-----
> From: tesla-bounces@xxxxxxxxxx [mailto:tesla-bounces@xxxxxxxxxx] On
> Behalf Of John Kirby
> Sent: Sunday, May 24, 2009 11:50 PM
> To: Tesla Coil Mailing List
> Subject: RE: [TCML] Capacitor encapsulent
>
>
> Gary,
>
> I think I have seen a table like this before, and the dielectric strength was also
> missing for HDPE. Do you (or anyone) know what it is?
>
> Regards,
> John K.
>
> --- On Sun, 5/24/09, Lau, Gary <Gary.Lau@xxxxxx> wrote:
>
> > From: Lau, Gary <Gary.Lau@xxxxxx>
> > Subject: RE: [TCML] Capacitor encapsulent
> > To: "Tesla Coil Mailing List" <tesla@xxxxxxxxxx>
> > Date: Sunday, May 24, 2009, 9:25 PM
> > Hi James,
> >
> > I've not been able to locate the dissipation factor for
> > common types of bottle and pane glass, but realize that all
> > plastics are not suitable. Here's a list of common
> > plastics with their dielectric constants and dissipation
> > factors. Plexiglas is PMMA, and its dissipation factor
> > is rather poor relative to PE and PP.
> >
> > polymer
> > dielectric
> > dielectric dissipation
> >
> > constant strength
> > factor
> >
> > 50Hz / 1Mhz (Kv/cm)
> > 50Hz / 1Mhz (x10^-3)
> > -------- -----------
> > -----------
> > -----------
> > LDPE 2.29 /
> > 2.28 370
> > .15 / .08
> > HDPE 2.35 /
> > 2.34 --
> > .24 / .20
> > PP 2.27 /
> > 2.25 240
> > .40 / .50
> > PVC-plasticized 4-8 / 4-5
> > 270
> > 80 / 120
> > PS
> > 2.5 / 2.5 200-300
> > .1-.4/.05-.4
> > ABS
> > 2.4-5/2.4-3.8 ~400
> > 3-8 / 2-15
> > PMMA
> > 3.3-3.9/2.2-3.2 140
> > 40-60/4-40
> > POM 3.7
> > / 3.7 400
> > 5 / 5
> > PTFE 2.1 /
> > 2.1 480
> > .2 / .2
> > PCTFE
> > 2.3-2.8/2.3-2.5 550
> > 1 / 20
> > PA-6 3.8 /
> > 3.4 400
> > 10 / 30
> > PA-66 8 /
> > 4 600
> > 140 / 80
> > PC 3.0 /
> > 2.9 380
> > .7 / 10
> > PET 4.0
> > / 4.0 420
> > 2 / 20
> > PI 3.5 /
> > 3.4 560
> > 2 / 5
> > PUR-linear 5.8 / 4.0
> > >300
> > 120 / 70
> > PUR-thermoset 3.6 / 3.4
> > 240
> > 50 / 50
> > PUR-thermoplas 6.6 / 5.6
> > 300
> > 30 / 60
> > CAB 3.7
> > / 3.5 400
> > 6 / 21
> > Silicone 3.6
> > 200
> > 5-13 / 7
> >
> > Regards, Gary Lau
> > MA, USA
> >
> >
> >
> > > -----Original Message-----
> > > From: tesla-bounces@xxxxxxxxxx
> > [mailto:tesla-bounces@xxxxxxxxxx]
> > On
> > > Behalf Of James
> > > Sent: Saturday, May 23, 2009 4:28 PM
> > > To: 'Tesla Coil Mailing List'
> > > Subject: RE: [TCML] Capacitor encapsulent
> > >
> > > Hi Ray, The problem with window glass is the iron in
> > it. The dielectric
> > > factor of window glass is POOR. Used as a Tesla coil
> > capacitor, it will
> > > crack and short your cap out. Use some form of
> > plastic. Polystyrene,
> > > polypropylene, Plexiglas, etc will be much better.
> > Now, you might wonder
> > > how I know this. It's a secret. James
> > >
> > > -----Original Message-----
> > > From: tesla-bounces@xxxxxxxxxx
> > [mailto:tesla-bounces@xxxxxxxxxx]
> > On
> > > Behalf Of Raymond Magdziarz
> > > Sent: Friday, May 22, 2009 6:38 PM
> > > To: tesla@xxxxxxxxxx
> > > Subject: [TCML] Capacitor encapsulent
> > >
> > > I'm building my capacitor using window glass and brass
> > sheets. I plan on
> > > using paraffin instead of transformer oil. I would
> > draw a vacuum on the
> > > container while the paraffin is liquid to get the
> > bubbles out and then
> > > let
> > > it solidify. Will this work, or what problems will I
> > have.
> > >
> > > Ray M.
> >
> > _______________________________________________
> > Tesla mailing list
> > Tesla@xxxxxxxxxxxxxx
> > http://www.pupman.com/mailman/listinfo/tesla
> >
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