Re: HV Capacitors - PTFE (fwd)

[<sroys@xxxxxxxxxxxxxxxxx>]

---------- Forwarded message ----------
Date: Thu, 23 Sep 2004 15:51:29 -0700
From: Ed Phillips <evp@xxxxxxxxxxx>
To: High Voltage list <hvlist@xxxxxxxxxx>
Subject: Re: HV Capacitors - PTFE (fwd)

High Voltage list wrote:
> 
> Original poster: <sroys@xxxxxxxxxxxxxxxxx>
> 
> ---------- Forwarded message ----------
> Date: Thu, 23 Sep 2004 08:47:28 -0500
> From: Carl Litton <Carl_Litton@xxxxxxxxxx>
> To: High Voltage list <hvlist@xxxxxxxxxx>
> Subject: HV Capacitors - PTFE
> 
> Our new local HV group is finding the securing or producing reliable,
> high capacitance capacitors at low cost for working in the 10's of kV
> range a serious challenge.
> 
> Commercial products found so far are completely out of the question in
> cost.  So much negative prose on the net about plate capacitors makes
> them unattractive.
> 
> The obvious use of 20 or 30 free MOT caps in a parallel/series array
> doesn't appear to be used so I'm assuming there is a dielectric
> breakdown problem associated with that.
> 
> In one of my other lives, I own a business that supplies chemical,
> tubes, fuse, etc. to hobbyists who build their own fireworks.
> Consequently, I have a fair amount of 400 micron PTFE (Teflon) powder on
> hand.  Somewhere on the net that I cannot relocate, it seems there
> information on the use this material in some very hot 'bucket' type
> capacitors.
> 
> Any ideas would be appreciated.
> 
> Carl Litton
> 901-374-5747

	You haven't said what capacitance values you're interested in.  The
guys on the various Tesla lists are using series strings of capacitors
in the range of 2500 VDC ratings; they're a dollar or so each.  Same
guys' experience says that many of the ultra-cheap carbon film
resistors  can stand the voltage if used to help divide the voltage in a
string.  Of course, maybe you can't stand the leakage of 10 megs at 2500
volts.

Ed