capacitor materials

Sent: 	Wednesday, June 18, 1997 3:40 AM
To: 	tesla-at-pupman-dot-com
Subject: 	Re: capacitor materials

--- Received from ETL.ETLNLHY +44-1483-303666        97-06-18 10:40

  -> IN=tesla(a)pupman-dot-com

In the UK polyethylene sheet can be purchased from Wickes hardware
shops for damp proof coursing.  It even comes in convienient 23cm
wide rolls.  Its looks just under a millimeter thick, and has a
criss-cross pattern on it (could be a problem with air bubbles?).
Costs about 6.50 a roll.

I've made three oil-filled capacitors with this plastic and
Bacofoil.  The're all still working. :-)



From: tesla-at-pupman-dot-com
To: tesla-at-poodle.pupman-dot-com
Mime-version: 1.0
Date: Tue, 17 Jun 1997 19:28:06 -0500

Subject:  Re: capacitor materials
  Date:  17 Jun 97 19:05:26 EDT
  From:  Alan Sharp <100624.504-at-CompuServe.COM>
    To:  "INTERNET:tesla-at-pupman-dot-com" <tesla-at-pupman-dot-com>


My thanks to Viv for putting me onto the possibility
of using 2mm clear polystyrene sheeting for capacitors - this
material is widely available in hardware shops here (UK) -
in B&Q and Do It All.
Cost is L11 -L13 per square meter.

Can anyone confirm that this material has a breakdown
voltage of 20 / 30 kV per mm, so 2mm should be OK
for up to 10kV AC in Tesla use?
Anyone tried it?

Dielectric constant is given as 2.5 which should give
a capacitance of 11nf per square meter.

Are there an snags to using this material ie dissipation
factor or weak spots?

Acrylic sheet is also available is this better or worse?

Polythene sheet .25mm is also available but will require
4-8 layers.

RS components also have plastic materials at inflated prices
ie 3mm polypropylene at L27 per square meter.


Alan Sharp (UK)

NB we use mainly the metric system here but I understand
that our imperial units are still loyally used in the
former colonies :)