Homemade Capacitor Formulas (Voltage and uF)?

[Magnethos]

I want to make a homemade capacitor, but I need to know how to configure (distances, etc...) the plates and the dielectric.

I want to make a 4000 Volt 30 uF Capacitor. What I need to calculate to obtain that real capacitor? What kind of dielectric I have to use... what space between plates...

Are information will be helpful

[nueview]

I'm with you on this one
but guess we're here all alone so want to share some information sure there is allot to learn i am looking for about 400 volts at 300UF so size and power will be different but once you know how the sky is the limit or maybe not .
bruce perrault has done allot of work on super capaciters and the like so may look him up .
i built some in the past and know you have to have good sized conducters to move the amp load it was my past problem let me do somemore research and i'll get back to you.
tension and dielectric strenght are going to be your big problems as i see it now plate area sprobably won't be.

[Magnethos]

Thanks nueview for your information,

I have some new information:
The basic theory: use 2 plates and a dielectric.

How to Calculate
C = A * eo * er / d

Where
A = plates surface
eo = dielectric permeability of the vacuum
er = relative dielectric permeability of the dielectric used
d = plate separation

[Kator01]

Hi Magnetos,

For high-voltage and high-power switching water-capacitors are used. Pure destilled water ( not the one you by in USA as destilled water in your supermarket - this is reversed-osmosis-water ) with very high inner resistance ( 2 MegOhm at least, better 10 Megohm ) is used.
I can not find the link anymore but I had found a company who uses water-caps for high-voltage-power-impuls in the Kilovolt range. Very pure water will have its dielectrical breakdown at 180 Kilovolt.

This one is very sientific, but shows you that this is used in multiterawatt pulsedpower
accelerators :

http://prst-ab.aps.org/pdf/PRSTAB/v9/i7/e070401

Here the specification for the pure water :
http://www.waterfuelconverters.com/SandiaNationalLabsData.html

At the bottom of this page you will find all necessary formulas :

http://www.waterfuelconverters.com/CapacitorCalculations.html

A simple version here :

http://www.instructables.com/id/DIY-Capacitor/

Another one here, more advanced, voltage must be checked -> glow-discharge :

http://home.earthlink.net/~lenyr/varelec.htm

http://home.earthlink.net/~lenyr/borax.htm


Hope this helps you to get the idea.

Please bear in mind that if you use ultrapure water you need an eloxadized surface ( insulating oxide-layer ) for
safety-reasons because any contamination will lead to a short if the plates are too close to each other.
You also can use a teflon-coating on the plateside exposed to the water but it is not easy to find a company which can do this. This is the reason why I put in the link "http://home.earthlink.net/~lenyr/varelec.htm" above because an oxide insulating layer is formed using baking-soda. Once you have the oxide-layer you then replace the salt-solution with ultrapure water after good chemical cleaning of the plates.

Regards

Kator01

[the_big_m_in_ok]

Hi Magnethos,

[/quote]
"The basic theory: use 2 plates and a dielectric."
[/quote]

Do you have time to experiment with aluminum foil and styrofoam cups?

Line the inside of a cup with aluminum foil and then do the same thing with the outside surface.  Experiment with the voltage tolerance and capacitance with a meter built for that purpose, if you have one.

The dielectric constant(s) for diffrerent grades of stryofoam certainly differ between manufacturers, but they're inexpensive and 'homemade' as you had asked for.

"Half Baked Idea" and suggestion.

--Lee
the_big_m_in_ok