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Liquid Dielectrics

Quoting Tim Chandler <tchand-at-slip-dot-net>:

> I have been messing around with liquid-dielectric plate 
> capacitors...

> Anyone else ever used or dealt with a plate capacitor 
> configuration using a liquid as a dielectric.  

I have built a couple of large oil dielectric capacitors.

> I have been messing with using deionized NH4, deionized 
> (distilled) H20, and glycerine.  Anybody have any better ideas
> for the liquid dielectric?

Oil, or even better, greasy wax.

> A liquid-dielectric capacitor would be quite configurable.  The
> temperature of the liquid dielectric effects the dielectric 
> constant, plates are easily added , corona and flashover should
> not be to much a problem seeing as the entire assembly 
> (conductor plate wise) is totally immersed in the dielectric 
> (no need to mess with transformer/mineral oil on top).  
> Dielectric breakdown due to inconsistancies in molecular
> structure (such as with polyethylene) is not as  big as concern
> as with film capacitors.  Just some thoughts... 

The big drawback in Tesla coil operation is plate vibration. The
plates have to be heavy (and copper this thick is not cost
effective) in order to resist flexing and the resulting breakdown
due to mechanical failures. Batting can be used as packing
between plates, but material choices here are limited due to the
high RF dissipation factors common to many dense fibrous
materials. Re-enforcing with solid dielectrics (acrylic,
polycarbonate, and old standby polyethylene) can be used as
packing between the plates, but you end up with so much packing
(required to supress vibration) that you might as well plan on a
solid dielectric capacitor to start. After trying many fixes, I
ended discarding this design for homemade capacitor
constructions.

> Also has anyone ever tried using a better conducting 
> electrolyte in salt water capacitors, does it improve 
> performance any?  

In liquid plate capacitors the conducting abilities of the plate
are not so important (because of the relatively huge volume and
large conducting surface area) as are the reduction of corona and
dissipation losses. This is where real gains can be made:
reducing the volume of the plates, effective corona supression,
and the use of plastic dielectrics.

Richard Quick


... If all else fails... Throw another megavolt across it!
___ Blue Wave/QWK v2.12