"John Bachman" wrote in message
...
On 29 Mar 2005 02:51:37 -0800, "Glynn R."
wrote:

Hey-- I've kinda wondered this too! In a circuit, I might choose a 16v
in a circuit I expect to have 5 volts running through. I have been told
I could put a 63v there and it works just the same. BUT, would it last
better? Would the extra expense do anything at all for reliability?

Reliability is generally improved by "derating" but only up to a
limit. Derating means operating the capacitor at a voltage less than
its rating, ie, a 25 volt capacitor operated at 15 volts is derated
15/25 = 60%. In other words, it is being operated at 60% of its rated
voltage.

Capacitor voltage ratings can be derated 25% - 100% depending on the
type but going beyond that is a waste of money and space except in the
most demanding applications.

John

Are there any other considerations; for electrolytic caps?
What I'm getting at is that an electrolytic capacitor rated at say 16
microfarads at say 450 volts DC, if operated at a very low voltage, lets
assume, say 25 volts for sake of argument, may not have the stated capacity
of 16 mfd. because of the manner of the electrochemical action of the
capacitor.
Or am I off track with this idea? Note this ? is only in reference to
electrolytic caps.

I have operated 2 mfd. 'paper' caps rated for 50v DC at 350v DC (with
ripple) knowing that they were tested to 2000v static DC when manufactured!
Also have operated similar 0.5 mfd. cap at 115v RMS (60 HZ.) in a fan
circuit with only one failure in 30+ years.

TIA