Capacitor rated values - what is 'current' thinking?
Posted: Sun Jan 29, 2012 5:53 pm
I seem to recall that the recommendations for electrolytic capacitors was to aim to run the voltage pretty high up to [but below] the rated voltage, because the oxide layers in the things build up thicker and 'adapt' to a high applied voltage over time [or conversely lose the ability to tolerate the rated voltage].
Not sure if this is still considered true for modern construction.
Anyhow, my immediate question is just to get the current view on where the optimum point of operating a capacitor is, and whether they can be operated up to the full rated value.
My issue is that I am putting some finishing touches to a high frequency power supply I started a long while back (I've mentioned this one to some of you before, off line). Back then, we were getting an excessive voltage here, over 253 V, which was bad for all sorts of reasons not least of which one of the power supply channels in this thing I'm building ran 25V electrolytics right up to the full 25V. The voltage is better improved these days, hitting a fairly well regulated 235V or so, giving 23V at the caps.
This is running through a regular bridge off a transformer. I added a load resistor to pull ~ 0.1A off the transformer at minimum (to stop the output voltage floating high, as some seem to do with no load at all).
So, I'm not sure I should be that concerned about running these 25V caps at 23V [should I be?] (they feed ~2 to 3A but get only very slightly warm to the touch, less than body heat) but I am concerned about what happens if the darned local voltage floats high.
What's the usual 'professional' recommendation these days on such matters?
Not sure if this is still considered true for modern construction.
Anyhow, my immediate question is just to get the current view on where the optimum point of operating a capacitor is, and whether they can be operated up to the full rated value.
My issue is that I am putting some finishing touches to a high frequency power supply I started a long while back (I've mentioned this one to some of you before, off line). Back then, we were getting an excessive voltage here, over 253 V, which was bad for all sorts of reasons not least of which one of the power supply channels in this thing I'm building ran 25V electrolytics right up to the full 25V. The voltage is better improved these days, hitting a fairly well regulated 235V or so, giving 23V at the caps.
This is running through a regular bridge off a transformer. I added a load resistor to pull ~ 0.1A off the transformer at minimum (to stop the output voltage floating high, as some seem to do with no load at all).
So, I'm not sure I should be that concerned about running these 25V caps at 23V [should I be?] (they feed ~2 to 3A but get only very slightly warm to the touch, less than body heat) but I am concerned about what happens if the darned local voltage floats high.
What's the usual 'professional' recommendation these days on such matters?