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Capacitor Voltage breakdown calculations

  • Thread starter hadronboy
  • Start date
  • #1
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Homework Statement


This is a general problem i have been having but if you are given the relative dielectric strength of a material, (take air, 1.00058986), i have then been told it can only handle a maximum of 3V/micro meter. i have then been given a question a asking what is the breakdown voltage of tantalum, (27) and a ceramic disk (1,000 - 10,000). im unsure how to work this out


Homework Equations


unsure what to use


The Attempt at a Solution


tried permitivity equations but nothing really worked, i first trying to work out the air example so that i then know the procedure to work out the others

Homework Statement





Homework Equations





The Attempt at a Solution

 

Answers and Replies

  • #2
berkeman
Mentor
57,520
7,539

Homework Statement


This is a general problem i have been having but if you are given the relative dielectric strength of a material, (take air, 1.00058986), i have then been told it can only handle a maximum of 3V/micro meter. i have then been given a question a asking what is the breakdown voltage of tantalum, (27) and a ceramic disk (1,000 - 10,000). im unsure how to work this out


Homework Equations


unsure what to use


The Attempt at a Solution


tried permitivity equations but nothing really worked, i first trying to work out the air example so that i then know the procedure to work out the others

Homework Statement





Homework Equations





The Attempt at a Solution

I'm not understanding the technique that they are asking you to use...

For air, you start with the Paschen curve (breakdown versus pressure for gasses):

http://en.wikipedia.org/wiki/Paschen's_law

You might check on the curve at atmospheric pressure to verify the 3V/um number you were given.

But I don't see how simply ratioing with dielectric constant will give you the insulator breakdowns. That certainly tells you how the E-field ratios, but I'm doubtful that it's just E-field that determines the breakdown. Unless they just want you to use that as a simplification....
 

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