[time-nuts] Replacing electrolytics - any disadvantages of high temp ones?

GMail / AnalogAficionado analogaficionado at gmail.com
Fri Jun 24 18:11:34 UTC 2011


Sorry to perpetuate the OT discussion, but there is an excellent series of articles by capacitor design engineer Cyril Bateman called Understanding Capacitors, published in EW&WW magazine in the late '90s.  The article on electrolytics covers almost anything you might want to know about them, and is a very worthwhile read.  I highly recommend the whole series.

Cyril had the articles posted on his own website some time ago, which I can no longer find.  But, they are still available online if you search around.

- Chad.


On Jun 23, 2011, at 9:10, "Dr. David Kirkby" <david.kirkby at onetel.net> wrote:

> On 06/21/11 08:39 PM, Poul-Henning Kamp wrote:
>> In message<4E008A73.50701 at erols.com>, Chuck Harris writes:
>> 
>>> and yet, I find that some electrolytic
>>> capacitors that have been run at lower than normal voltage improve markedly
>>> when "reformed" by applying  rated voltage through a 10K resistor for a
>>> couple of hours.
>> 
>> I noticed in a datasheet at one point, that the capacity only was
>> warranted above a certain percentage of rated voltage.  No explanation
>> was given.
>> 
> 
> Note on the link posted by Robert LaJeunesse:
> 
> 
> http://www.cde.com/catalogs/AEappGUIDE.pdf
> 
> 
> it says voltage derating gives better reliability:
> 
> 
> ======================================
> "Aluminum electrolytic capacitors made with formation voltages
> at least 35% higher than rated voltage and with rated tempera-
> tures of 85 oC or higher, don’t require much voltage derating. In
> applications operating at less than 45 oC no derating is needed,
> and with up to 75 oC, 10% is sufficient. For higher temperatures
> and with high ripple current, 15% or 20% is appropriate. Since
> operating life continues to increase for further derating, military
> and space applications use 50% voltage derating."
> ========================================
> 
> I've herd stories one should not operating caps well below their rated voltage, but that would tend to suggest that is not so.
> 
> -- 
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> Q: Why is top-posting such a bad thing?
> A: Top-posting.
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> 
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