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Forum: Reliability & Maintainability Questions and Answers

Topic: Reliability & Maintainability Questions and Answers

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

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Original Message:

Posted by: Kevin Silke
Date posted: Wed Jun 20 12:48:40 US/Eastern 2001
Subject: Power Inductor Derating
Message:
Derating criteria for inductors seems to vary depending on who's doing the derating and their reference guidelines, except that they all seem to include temperature as a criterion. So my question is if you have multiple derating criteria (say current and temperature) and you don't satisfy the first criterion but you do satisfy the temperature criterion, are you adequately derated?


Reply:

Subject: Derating Inductors
Reply Posted by: Bruce Dudley (bdudley@alionscience.com )
Organization: Reliability Analysis Center
Date Posted: Thu Jun 21 13:47:16 US/Eastern 2001
Message:
Derating parameter listed in reference documents are not fixed in stone values that cannot be deviated from. The idea of derating components is to reduce the stress levels so that improved reliability can be attained. The derating parameters in most handbooks are based on engineering experience conditions, hence a value exceeding these rates is not a reason to panic, in fact it might be reasonable when other conditions are integrated. The condition that you have noted, temperature and current for inductors, is a common occurrence as temperature and current loads are interrelated. The RAC derating guide, “Electronic Derating for Optimum Performance” indicates that temperature should be the most important parameter affecting the device reliability. In effect, derating temperature should cause a derating of current as the current load impacts the overall “hot spot” temperature. A combination derating should derate the temperature first and the current second.


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