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Forum: Reliability & Maintainability Questions and Answers

Topic: Reliability & Maintainability Questions and Answers

Topic Posted by: Reliability & Maintainability Forum ( )
Organization: System Reliability Center
Date Posted: Mon Aug 31 12:47:36 US/Eastern 1998

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Posted by: Rushabh
Date posted: Mon Mar 5 15:13:43 US/Eastern 2007
Subject: Why failure rate of a capacitor is higher for non-operating vs operating condition
Can you please try to find the failure rate with 10% duty cycle ? I might be that for 0% duty cycle calculation there is some bug in software. Ideally what you pointed out is correct. Operating mode failure rate should be higher than Non Operating.

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Subject: Capacitor Failure Rate
Reply Posted by: John Cloarec
Date Posted: Mon Mar 5 16:44:41 US/Eastern 2007
Ananya, I thimk your problem is based on the fact that you are using negative temperature. If you look to MIL HSBK 217, section 3.4.1, it is stated "Extrapolation of any of the base faihn rate models beyond the tabulated value such as high or subzero temperature, electrical stress values above 1.0, or extrapolation of any associated model modifiers is oompletety invalid". If you look to the table supporting the Lambda/b calculation for capacitors, they all begin to 0C until 5C before the Max Rated Temperature. Your problem is not due to your duty cycle but to temperature. Regards, John.

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