On 30 Jan 2005, at 11:51, Tesla list wrote:
> Original poster: FIFTYGUY@xxxxxxx
>
> In a message dated 1/29/05 11:23:47 PM Eastern Standard Time,
> tesla@xxxxxxxxxx writes:
> P.V.C has a very high dissipation factor, they actually use radio
> frequency to weld P.V.C. (albeit at a very high frequency) I do not
> recall the exact figures but polyethylene and styrene both have rather
> low dissipation factors. (anyone have a C.R.C. handbook handy?)
>
> Could not find dissipation factors in my 83rd ed. of the CRC
> "Handbook
> of Chemistry and Physics."
> My 2nd ed. of the "Polymer Handbook" lists the following
> dissipation
> factors (at 60 Hz!):
>
> Poly(methyl-1-pentene) .00007
> Poly(styrene), general purpose .0001-.0006
> Poly(styrene), high impact .0004-.002
> Poly(styrene), high heat .0005-.003
> Poly(ethylene), {low, med, and hi-density] <.0005
> Poly(propylene) <.0005
> Poly(carbonate) <.0009
> Epoxy cast resins .002-.010
> Poly(vinyl chloride) .007-.020
> Poly(vinyl chloride), chlorinated .021-.019
> Poly(vinylidene chloride) .03-.045
>
> Also lists "Arc Resistance, ASTM-D-495[s]", with Cellulose
> Acetate,
> Poly(ethylene) med density, and Poly(imide) at the top,
> Poly(propylene) high, Nylon 66 and Poly(styrene) middle, Polycarbonate
> and Epoxies lower, and Poly(vinyl chloride) at the bottom.
> From the 1st ed. of the McGraw-Hill "Electronics Engineers'
> Handbook",
> a table from "Standard Handbook for Electrical Engineers", 10th ed.",
> properties of insulating films. Include dissipation factors at various
> frequencies:
>
> Material: dissipation factor @ 10^3/
> @ 10^6 Hz
>
> TFE tetrafluoroethylene .0002/.0002
> Polyethylene .0003/.0003
> Polyimide .0003/.0010
> Polypropylene .0003/.0003
> Polyurethane elastomer .06/---
> Cellulose acetate .10/.10
> Polyamide .010/.016
> Vinylidene chloride .045/.075
> Polyvinyl chloride .16/.14
>
> So it would appear that polystyrene is low dissipation, and PVC
> sucks.
> However, my gut feeling is that this is purely academic, since I've
> read that after breakout the Q plummets to a whopping 6 or so. I'm
> guessing a typical secondary coil form won't dissipate more than a
> percent or two of the total energy of a typical TC. I would also guess
> drying to remove water content would more help prevent losses through
> breakdown than from dissipation.
> I bet the secondary wire has more losses than the coilform,
> although
> again due to low post-breakout Q it can't be that important. If the
> standard model shows a series 220K Ohm resistance in the streamer, I'd
> work to make the air more conductive to cut losses!
> I think the only folks who would have to worry about coilform
> dissipation factors are those running in high-power CW.
>
> > Ideally no core at all would be best, Styrofoam is about as close
> as > your going to get to no core at all.
>
> Or a form-less coil. But I think it would be fragile compared to
> a
> coil that retains its former. One of these days I'll get around to
> making one - I bought the electrical epoxy to do it, and made up the
> former. At the moment, I'm happy with the scrap SDR sewer pipe I've
> been scrounging for free.
>
> -Phil LaBudde
I have a spacewound secondary wound on some thickwall sewer pipe
(no previous sealing or other treatment) which has a Q in excess of
300 at 165kHz. With Q's that high, differences in dielectric
dissipation are a non-issue. The only secondary I wound which came a
cropper was wound on some sonotube-type stuff with the tar paper
removed. It was largish, spacewound and its Q barely clocked in
around 40 with powered results to match. It was varnished but I
didn't bother to dry the stuff prior to coating. My fault of course.
Malcolm