On 2/25/19 5:48 AM, Bob kb8tq wrote:
Hi
Indeed there is both a minimum and a maximum working voltage for a properly
derated electrolytic
capacitor. We found that out in the middle of a design review when the
customer’s team brought it
up … (much to our surprise).
Bob
The Cornell Dubilier app guide doesn't seem to mention it.
http://www.cde.com/resources/catalogs/AEappGUIDE.pdf
NAVSEA derating guidelines make no mention of it:
https://www.navsea.navy.mil/Portals/103/Documents/NSWC_Crane/SD-18/PDFs/Products/Capacitors/CapacitorsDeratingRevB.pdf
They're both appear to be focused on essentially setting a lower voltage
as a thermal consideration, and not on a "giving you more margin to
failure voltage".
https://www.illinoiscapacitor.com/pdf/Papers/reliability_of_capacitors_general.pdf
says you only get a max of twice rated life by derating. Maybe that's
because of the "reforming of the dielectric to a thinner layer"..
This is a compendium from 1981 of all sorts of capacitor information but
doesn't seem to address derating.
https://ntrs.nasa.gov/archive/nasa/casi.ntrs.nasa.gov/19810017835.pdf
https://ntrs.nasa.gov/archive/nasa/casi.ntrs.nasa.gov/20160003309.pdf
has a lot of info on wet slug tantalums..
On Feb 25, 2019, at 1:48 AM, Poul-Henning Kamp <p...@phk.freebsd.dk> wrote:
--------
In message
<CADHrwpcdmyeguXoM69D2byW=DfKwMfi7_t-P=qYst7T7OO=e...@mail.gmail.com>, Dana
Whitlow writes:
This would seem to imply that purposely overrating a 'lyt is pretty pointless.
Any comments on this notion?
I've always wondered that myself, and found very little documentation or
wisdom available.
As I understand it, even very brief voltage spikes must be kept under the
rated voltage, so overrating would buy some transient durability, but
other than that...
--
Poul-Henning Kamp | UNIX since Zilog Zeus 3.20
p...@freebsd.org | TCP/IP since RFC 956
FreeBSD committer | BSD since 4.3-tahoe
Never attribute to malice what can adequately be explained by incompetence.
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