[ARC5] Reforming Electrolytics attached as PDF

[Robert Nickels]

Sometimes it seems that folklore overrides science when it comes to 
certain components, including capacitors in general.  But the more we 
understand about how they are made, the easier it become to properly 
apply, maintain, and diagnose problems with them.

Rubycon, a major electrolytic capacitor manufacturer in Japan, has 
published a good explanation of the major steps in its manufacturing 
process here:

www.rubycon.co.jp/en/products/alumi/pdf/Process.pdf

When one understands the importance of "forming" of the dielectric layer 
and subsequent "reforming" after assembly as  key steps in the 
manufacturing process, it makes sense  why reforming is also required 
after a period of storage to repair damage to the oxide film and 
stabilize the capacitor.     As I mentioned in an ER article on this 
subject, the instructor the wind turbine technology program at the local 
community college told me that manufacturers such as ABB state that 
capacitors used in converters, variable speed drives, and other power 
system devices  must be reformed if the device has been non-operational 
for more than one year.   Those instructions can be found online as 
well, and given the importance of reliability in the power generation 
industry, it's something students are trained on before becoming certified.

The capacitors in our radios are treated much more gently, but they're 
still subject to the same laws of physics and chemistry.

73, Bob W9RAN