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Re: LDPE and HDPE/0.08uF cap hints
From: David Huffman[SMTP:huffman-at-FNAL.GOV]
Sent: Thursday, July 17, 1997 11:23 AM
To: Tesla List
Subject: Re: LDPE and HDPE/0.08uF cap hints
I need a large cap for my H&R transformers also. I recently purchased
65lbs. of 8 mil poly, a 20" wide roll for $15. A great deal, thank
you Bert H. for the tip. I will make a flat unit and would like to
know how many layer of 8 mil poly would be safe for the 10KV max the
H&R might put out. I know the voltage rating per mil increases as the
thickness decreases as Richard states below. How can this be
interpreted for say a single 8 mil layer? The more I think about this
the more confusing it seems to be. I may not what to use a single
layer since a defect would mean cap failure, however increasing the
number of layers makes poor use of the voltage rating. I also doubt a
visual inspection of the plastic would find defects the voltage might
push through. I'm sort of settling in on 2 layers of poly in each
section and then 4 sections in series.
Still looking for containers to put the cap and transformer in too.
Dave Huffman
----------
> From: Tesla List <tesla-at-pupman-dot-com>
> To: 'Tesla List' <tesla-at-poodle.pupman-dot-com>
> Subject: Re: LDPE and HDPE
> Date: Thursday, July 17, 1997 10:12 AM
>
>
> From: richard hull[SMTP:rhull-at-richmond.infi-dot-net]
> Sent: Wednesday, July 16, 1997 7:53 PM
> To: Tesla List
> Subject: Re: LDPE and HDPE
>
> At 07:19 AM 7/16/97 -0500, you wrote:
> >
> >From: Jason Judd[SMTP:jason.judd-at-anu.edu.au]
> >Sent: Wednesday, July 16, 1997 1:25 AM
> >To: Tesla List
> >Subject: LDPE and HDPE
> >
> >Hi folks,
> >
> >recently I decided to have a go at making a new capacitor. I
choose to do a
> >rolled cap . When looking for the polyehylene sheeting I could
only find
> >high density and ulta high density sheets. Since then I have heard
> >reference to low density or LDPE. Can someone explain to me what
this means
> >in terms of dielecric strength and K value.
> >
> >
> >Thanks
> >
> >Jason
> >
> >
> >
> >Jason,
>
> No real diff so far as caps are concerned. The high density stuff
has an
> edge in heat handling and a slight edge in voltage. Don't pay more
for the
> higher density grades. LDPE is just fine for all uses in Tesla
caps.
> Strength on LDPE is rated real high 3000-5000v/mil in .5mil
thicknesses
> (DC). In thick slabs >50 mil it drops drastically to 200v/mil (AC
shock
> excited). K is around 2.3-2.5
>
> Richard Hull, TCBOR
>
>
>