"Fred McKenzie" wrote in message
...
In article . com,
wrote:

this might be a bit off topic, however is there a (easy or not) way to
tell the working voltage of a ceramic disc capacitor? I have tons of
these surplus or saved capacitors but often the working voltage is
marked when equal or higher than 1 kV. When I have to reuse a capacitor
in a high but not so high voltage circuit (let's say 200 Vdc) I never
know how to find the correct size or how to measure the insulation
voltage of the capacitor.

Francesco-

A problem with determining a capacitor's voltage, is that the test can
be destructive. Once the insulation resistance has broken down, the
capacitor is most likely no longer unusable.

For ceramic capacitors, you can take a chance and apply twice the
expected working voltage and verify there is no leakage after the
initial charging has occurred. Some capacitor testers have a capability
to do this test.

Dielectric stress tests should be run for a long period of time, if you
really want to be sure.

If the OP has lots of capacitors and the ability to safely test at high
voltages, then destructive testing is an option. One determines the failure
voltage and then extrapolates the safe working voltage from that (more than
one unit must be failed, to be reasonably sure).

High-capacity ceramics might be safe at 50 dcwv, or so. Moderate capacity
ceramics are probably OK at 100 to 200.