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

 

Out of curiosity - why a variable capacitor? what will be the application?

 

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

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

 

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.

 

Out of curiosity - why a variable capacitor? what will be the application?

It for use as a power generation device. A sort of charge pump. Converts mechanical energy to electrical

 

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

Thank for the info. What is the dielectric strength of SF6 at 14psi?

 

Thank for the info. What is the dielectric strength of SF6 at 14psi?

Here is some data from MV HV breaker research. 14psi is about 1 bar of pressure.

http://www.cahiers-techniques.schne...s-switchgear/high-voltage-plus-1kv/ect171.pdf

General HV text.

http://www.scribd.com/doc/21112291/High-Voltage-Engineering