film capacitor life test

[anilresat]

Hi everybody,
I am curious about how to test film capacitor's life. What are the
main parameters that effect a film capacitor's life? Also, are there
any circuit designs that you can recommend me to test these parameters
or generally the life of the film capacitor? Thanks.

 

[John Larkin]

On Mon, 25 May 2009 02:15:55 -0700 (PDT), anilresat
<manilresat@gmail.com> wrote:

Hi everybody,
I am curious about how to test film capacitor's life. What are the
main parameters that effect a film capacitor's life? Also, are there
any circuit designs that you can recommend me to test these parameters
or generally the life of the film capacitor? Thanks.

Commercial film caps have failure rates in the 5 FIT ballpark, where
one FIT is one failure per billion hours. So you'd have to run a
million caps for thousands of hours to get decent failure rate
statistics. The cap manufacturers probably test fewer numbers at high
temperature or whatever and apply stress factors to get their FIT
estimates.

You can stress a small number of caps to failure, voltage and
temperature (and AC current, if it matters) to see what sorts of
margins you have.

Decent film caps essentially don't fail if not abused. They seldom
fail *if* abused.

John

 

[David L. Jones]

anilresat wrote:

Hi everybody,
I am curious about how to test film capacitor's life. What are the
main parameters that effect a film capacitor's life? Also, are there
any circuit designs that you can recommend me to test these parameters
or generally the life of the film capacitor? Thanks.

Temperature and voltage/current are the main parameters, but there are
others.
This stuff comes down to accelerated testing at extremess and involves
statistics and other inferences. It is difficult to understand/implement
this type of testing unless you are the manufacturer.
*why* do you want to do this?

Dave.

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