[R-390] Cap Voltage

[Bob Camp]

Hi

AC caps are rated for RMS volts plus surge. DC caps are rated for DC volts plus surge. RMS to DC usually is a 1.414 sort of thing. The surge numbers - that depends, 20% is not uncommon. On some parts (rated by marketing) the number is 0%. (Long ago 450 was the max on electrolytic caps, one company sold 550 volt parts … check the fine print …). 

Current is the bigger issue. AC caps likely are designed for a specific frequency (or range) and an anticipated continuous current. DC caps are rated for a peak discharge current (as in you short the cap). 

Simple answer - they are different beasts.

Bob

On Jul 21, 2014, at 1:02 AM, Roger Ruszkowski <flowertime01 at wmconnect.com> wrote:

> 
> Fellows,
> 
> I forgot what I read.
> There was once thread on AC caps and how much DC voltage could be used on them in a power supply.
> If my cap is marked 400VCA 20UF how much DC can I apply to the cap if I use it as a filter cap in a DC power supply and want it to last?
> 
> Thanks
> 
> Roger AI4NI
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