capacitor voltage rating

[akis]

can i use a 35V capacitor with 38V DC? is that within its tolerance or will it leak/explode over time?

[Frank Berry]

You should use a 50V cap.

[Enzo]

Caps usually come with a "working voltage" rating. That means they are designed to work at or near the voltage printed on them. Or at lower voltages, of course.

Caps also have a surge voltage rating. Usually found in the data sheet. When I was learning my basic electronics in the 1950s, it was common for large aluminum can caps to have both working voltage and surge voltage printed on them.

A 500wv - 500 working volts - cap would work fine at 500v all day long. It might have a surge rating of 550v or even 600v. That meant that the cap would handle BRIEF exposure to those elevated voltages without failing. This was to handle situations like initial power up, when voltages could swing way high before circuit currents brought them back down to normal.

But running a 500WV cap at 540v all day would lead to its shortened life and early failure.

Frank's 50v cap would be the better choice for you, and really, the cost difference is a few pennies. When it is that inexpensive to do it right, why do it wrong?

[nigelwright7557]

I had a class d amp that was bus pumping and it pushed up the supply voltage over the cap rating and the capacitors started to get warm.