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Re: safety gaps on capacitors



Original poster: "Bert Hickman by way of Terry Fritz <twftesla-at-qwest-dot-net>" <bert.hickman-at-aquila-dot-net>

Ralph and all,

Commercial oil capacitors always use use a composite dielectric system
consisting of either metal-oil-dielectric (multiple layer)-oil-metal or
metal-oil-paper-polymer film (multiple layer)-paper-oil-metal. The main
dielectric in older oil (or PCB) filter caps was often specially produced
kraft paper with few impurities or pinhole defects. Newer oil caps use
Mylar as the primary dielectric Some even newer caps that are intended to
see AC or high ripple current may use polypropylene as the main dielectric. 

When used in their intended design application (typically as DC filter
caps), they are very reliable. However, older oil caps pressed into Tesla
Coil tank service have been known to explode, often with no prior warning.

-- Bert --
-- 
Bert Hickman
Stoneridge Engineering
Email:    bert.hickman-at-aquila-dot-net
Web Site: http://www.teslamania-dot-com

Tesla list wrote:
> 
> Original poster: "by way of Terry Fritz <twftesla-at-qwest-dot-net>"
<Parpp807-at-aol-dot-com>
> 
> Gary and John,
> Obviously, since the case of an oil filled cap can be connected to the
> chassis, ground usually, there must be some sort of internal case such as a
> vitreous substance.
> I though that the plates were submerged in the oil bath (pcb back in the good
> days)
> with each set of plates suspended from a hanger arrangement forming one
> external terminal. So construction must vary from one manufacturer to
annuder.
> Also, what would be a variation in the quality? I have nothing but CD or
> Sprague
> oil filled caps  working in my amplifiers and have never known one to fail. I
> would guess that unless they are frequently over-volted to arc internally and
> leave a lot of carbon in the oil, they are largely indestructable.
> 
> Happy day,
> Ralph Zekelman