Capacitor dielectrics?

Discussion in 'The Projects Forum' started by A mc, Feb 2, 2010.

  1. A mc

    Thread Starter New Member

    Feb 2, 2010
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    I’m trying to get up too speed with the state of the art on capacitor dielectrics. I’m hoping to build a high energy storage variable capacitor. Because I want the plates of the capacitor to move I was thinking a gas or liquid is more suitable. To get the energy density I want I need high permittivity and high dielectric strength

    I’ve done a bit of reading, I’ve found the following

    Oils Er= 2 to 4 @ 100 to 140 kV/cm
    SF6 Er= 2 to 4 @ 600kV/cm Container would need to be pressurised and such high voltages would incur other problems

    alkylene carbonates Er=80 @ 100 to 500KV/cm liquid is quickly contaminated and dielectric strength drops rapidly.

    I’m hoping someone can point me in the direction of new materials with good properties

    thanks
     
  2. beenthere

    Retired Moderator

    Apr 20, 2004
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    Out of curiosity - why a variable capacitor? what will be the application?
     
  3. nsaspook

    AAC Fanatic!

    Aug 27, 2009
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    I would recommend SF6. It's basicly inert and easy to use. Just pump the vessel to vacuum then pressurize to about 14 psi. I use the stuff for rf hi-voltage resonators at work.

    http://www.aibt-inc.com/pdf/IITConference-High_Efficiency.pdf
     
  4. rjenkins

    AAC Fanatic!

    Nov 6, 2005
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    If you charge a variable capacitor whilst it is set to maximum capacitance, then isolate it and decrease it's capacitance, the voltage on it increases.

    It is one method of creating extremely high voltage.
     
  5. A mc

    Thread Starter New Member

    Feb 2, 2010
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    It for use as a power generation device. A sort of charge pump. Converts mechanical energy to electrical
     
  6. A mc

    Thread Starter New Member

    Feb 2, 2010
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    Thank for the info. What is the dielectric strength of SF6 at 14psi?
     
  7. nsaspook

    AAC Fanatic!

    Aug 27, 2009
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