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 :)
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.
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
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 (http://prst-ab.aps.org/pdf/PRSTAB/v9/i7/e070401)
Here the specification for the pure water :
http://www.waterfuelconverters.com/SandiaNationalLabsData.html (http://www.waterfuelconverters.com/SandiaNationalLabsData.html)
At the bottom of this page you will find all necessary formulas :
http://www.waterfuelconverters.com/CapacitorCalculations.html (http://www.waterfuelconverters.com/CapacitorCalculations.html)
A simple version here :
http://www.instructables.com/id/DIY-Capacitor/ (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/varelec.htm)
http://home.earthlink.net/~lenyr/borax.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
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
so poor...
Quote from: dankie on March 28, 2009, 06:25:17 PM
so poor...
@dankie,
Well,okay. Could you be more specific?
Before you answer, I assert that I remember this information as being more than merely *cost effective* awhile ago (years) from an Internet site devoted to high voltage experimentation. 20-30 KV capacitors cost a lot and a string of these in series can be built for much less. They need to be carefully built and not exceeded in thier voltage capacity, or arcing and/or foil burn-through will result, obviously. Adequate testing and quality control is required, but if it's done, you will have saved a significant amount of money. The diligent experimenter will need to decide if it's worth the effort.
I didn't invent these, someone else did, and I've only had the wherewithal to study and research literature on high voltage up to the present.
tRULY HIGH VOLTAGE CAPACITERS ARE IN A WORLD OF THERE OWN
i say this because i tryed building some at one time in the past and found that transformer oil from your local power utility works really grreat it is a good stable fluid but even it will break down due to sharp edges on the foil or even a sharp bump on the surface corners are a deffinate no go round is best and open plates in a tank of oil gives good adjustment but the plates will flex under that tension any additional supports should be of equal or better dielectric value or they will conduct as well any air in your fluid can also cause arcing after a certain tention the larger it gets the more dangerous it will become so always leave it shorted when its just sitting around as it can accumulate a charge.
Quote from: nueview on March 29, 2009, 10:25:22 AM
tRULY HIGH VOLTAGE CAPACITERS ARE IN A WORLD OF THERE OWN
"...transformer oil from your local power utility works really grreat it is a good stable fluid"
>>Good, I agree. Awhile ago power companies used sulfur hexafluoride (SF6), since it's nontoxic and unreactive toward many materials. Good dielectric, too. What it did do was form a sub-compound, trifluoro methy sulfur pentflouride (CF3SF5), which was a gas, rather than a liquid originally in the transformer. Today, more stable compounds are being tried.
"but even it will break down due to sharp edges on the foil or even a sharp bump on the surface corners are a deffinate no go"
>>I agree. Sharp edges will cause coronal discharge in such thing as high voltage multipliers like Cockroft-Walton and others.
"...round is best and open plates in a tank of oil"
>>Your statement reminded me that the description in my posting above should have had appended to it: The homemade capacitor should also be immersed in a dielectric liguid, like oil. This will increase the voltage carrying capacity of the capacitor(s). Because styrofoam is made of hydrocarbon Styrene, mineral oil might be okay, as long as the styrofoam doesn't disolve in the dielectric liquid.
"air in your fluid can also cause arcing after a certain tention"
>>Right. I have some professional experience in high voltage R&D, and I agree. Air could easily break down before some higher density liquid dielectric compounds.
"...the larger it gets the more dangerous it will become so always leave it shorted when its just sitting around as it can accumulate a charge."
>>This would have free energy applications, wouldn't it? Place a zener diode or a string of them across the terminals in which the zener(s) have a threshhold lower than the dielectric. This would periodically short the terminals which could have a step down transformer in wired parallel agross the zener(s)/transformer, to a diode and a battery.
Spark gaps in inventions from the early 1900's worked the same way for free energy applications. An automobile spark plug is obviously a more modern adaptation.
Quote from: nueview on March 29, 2009, 10:25:22 AM
tRULY HIGH VOLTAGE CAPACITERS ARE IN A WORLD OF THERE OWN
"...transformer oil from your local power utility works really grreat it is a good stable fluid"
>>Good, I agree. Awhile ago power companies used sulfur hexafluoride (SF6), since it's nontoxic and unreactive toward many materials. Good dielectric, too. What it did do was form a sub-compound, trifluoro methy sulfur pentflouride (CF3SF5), which was a gas, rather than a liquid originally in the transformer. Today, more stable compounds are being tried.
"but even it will break down due to sharp edges on the foil or even a sharp bump on the surface corners are a deffinate no go"
>>I agree. Sharp edges will cause coronal discharge in such thing as high voltage multipliers like Cockroft-Walton and others.
"...round is best and open plates in a tank of oil"
>>Your statement reminded me that the description in my posting above should have had appended to it: The homemade capacitor should also be immersed in a dielectric liguid, like oil. This will increase the voltage carrying capacity of the capacitor(s). Because styrofoam is made of hydrocarbon Styrene, mineral oil might be okay, as long as the styrofoam doesn't disolve in the dielectric liquid.
"air in your fluid can also cause arcing after a certain tention"
>>Right. I have some professional experience in high voltage R&D, and I agree. Air could easily break down before some higher density liquid dielectric compounds.
"...the larger it gets the more dangerous it will become so always leave it shorted when its just sitting around as it can accumulate a charge."
>>This would have free energy applications, wouldn't it? Place a zener diode or a string of them across the terminals in which the zener(s) have a threshhold lower than the dielectric. This would periodically short the terminals which could have a step down transformer in wired parallel agross the zener(s)/transformer, to a diode and a battery.
Spark gaps in inventions from the early 1900's worked the same way for free energy applications. An automobile spark plug is obviously a more modern adaptation.
Actualy the charge build up is from earth tide movement and space celestial tention which is left behind in the capaciter it allows a momentery look at a charge locked from that moment in time of discharge and the dielectric will hold it to some other time and tension will build to the outside it could be quite large normally this will blead off over time but dry air conditions and seperation from ground can cause it to build to quite a residual charge so always short them and ground them when not in use just to be careful.