Actually I said nothing whatsoever about derating capacitors or any other component. Try reading again what I did say.

and do not work well at a much lower voltage.

What I did not say, and you could very well have done but did not say, was that
some ratings refer to working conditions and some even allow variation,

Some ratings refer to maximum values, where an undesireable effect will occur if exceeded.

And some ratings even refer to minimum values that are offered or must be provided for the device to function correctly or even at all.

Further some of these ratings are set by the rest of the circuitry and some are characteristics of the device, guaranteed by the manufacturer.

Now whole books and umpteen pages of standards have been written about device ratings. It would certainly be inappropropriate to attempt to reproduce here in a forum.

Yet you enter the lists with the slogan

My purpose was to correct incorrect information, and supplement incomplete information you gave.

Why was this not a personal attack?
How can I be expected to supply the complete information about all device ratings?
And how have you supplemented this deficiency? Is your information complete?

Further what incorrect information have you 'corrected'

 

Actually I said nothing whatsoever about derating capacitors or any other component. Try reading again what I did say.

You said "Electrolytic Capacitors are designed to operate at or near their rated voltage, and do not work well at a much lower voltage."

It's true that you didn't use the actual word "derating", but you did use the word "rated". It's clear that you were saying that capacitors don't work well if much "derated" with respect to the voltage for which they are "rated".

My purpose was to correct incorrect information, and supplement incomplete information you gave.

Why was this not a personal attack?
How can I be expected to supply the complete information about all device ratings?

I don't think that anybody who posts on this forum is expected to supply the complete information about all device ratings. But you seem to be suggesting that if somebody does post incomplete information, it constitutes a personal attack for somebody else to post supplementary information. I would hope that someone who may know something more about a topic would be able to post it without fearing that it will be taken as a personal attack.

If somebody posts incorrect information, is everybody else expected to refrain from posting a correction because it may be taken as a personal attack? Is disagreement disallowed? I certainly hope not.

Isn't the point of the forum to share information?

And how have you supplemented this deficiency? Is your information complete?

In post #9 where I said "But, if the environment is liable to subject the diode to occasional overvoltage spikes, there are so-called controlled avalanche diodes specifically designed not to be destroyed by such events:"

And I gave a link:

http://www.bing.com/search?q=contro...s=0&ppfsrcig=520a73a349834dd1b0b8a77c8dded09f

Of course my information may not be complete. I never said it was complete; I said it was supplementary. If somebody has even more information on the subject, then I hope they will post it.

Further what incorrect information have you 'corrected'

The first bit I noticed was when you said "Diodes are rated for RMS current. That is a 1 amp diode is rated to run at 1 amp RMS (or less) for its entire service life." This is incorrect. The manufacturers rate them according to average current, not RMS current. I posted a number of data sheets which illustrate this.

Since in capacitor input power supplies the diode current is typically delivered in relatively narrow pulses, the average value of those pulses is rather different from the RMS value. When selecting a diode the manufacturer's rating method should be used, which is average current.

My purpose in pointing this out was to help the OP avoid using an incorrect rating method for rectifier diodes.

I think you are quibbling now, and I've said all I have to say on these matters.