Re: More cap tuning

"Ian Iveson" <IanIveson.home@xxxxxxxxxxxxxxxx> wrote in
message news:DAtym.4517$xd4.4046@xxxxxxxxxxxxx
Peter wrote:

50V caps have no place in tube equipment.

I've used them for small valve cathode bypass. Less
reliable than a higher voltage, but adequate, and cheap
and compact. Temperature rating is also important for
longevity, presumably.

What's the difference, in terms of construction, between
electrolytics rated for different voltages?

http://archive.chipcenter.com/eexpert/akruger/akruger006.html

"Dielectric Thickness.

"Several metals, such as tantalum, aluminum, niobium, zirconium and zinc,
can be coated with an oxide film by electrochemical means. For example, by
placing aluminum in appropriate solution and passing a current though the
circuit, a thin layer of aluminum oxide (Al2O3) forms on the aluminum anode.
It is this thin oxide film that is the dielectric in an electrolytic
capacitor, and the electrolytic process used for creating the dielectric
gives the name "electrolytic capacitor". The thickness of the oxide layer
depends on the formation voltage, which is typically 3-4 times higher than
the rated voltage, but it is very thin: less than a micrometer.
"

Note:

"The thickness of the oxide layer depends on the formation voltage, which is
typically 3-4 times higher than the rated voltage, but it is very thin: less
than a micrometer."

Anodizing aluminum for 450 volt electrolytics would appear to be something
that takes a lot of care due to the safety issues.


.

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