How to confirm AC power capacitor 100% OK?
For an example a 200uF 250Vac power capacitor,
I have came across by using multimeter to check its uF,resistance eventhough is ok,but when putting it to the unit,it didn't work.
Any other methods can confirm it is 100% ok?

 

Hi Wkyong,

Interesting.
That sounds like a serious capacitor.
Maybe for some motor ?

Simple checks first to see it doesn't leak,
and on high impedance ohm-meter check, i would expect to see some rise-time, just to
be sure its a capacitor.

Then i would probably give it DC checks by charging it to the supply voltage via a diode
and series resistor, with a meter across it to see that it gets up to a little over 250 volts,
maybe 280 v would be acceptable, I would expect it to hold at 300. Depending on wether or not it
has an internal bleed fitted.

I would see that it was satisfactory in both directions on DC,
then maybe put it back into service.

Or if it was desired to see that it acts as an AC capacitor, maybe put it in series with some
load across the AC supply.
Maybe a filament lamp, but thats not going to give it much of a 'ripple test'
Maybe a one bar electric fire element, or even an electric kettle in series might be a more
realistic load.
If it behaved as expected with a 3Kw kettle in series,
i would be inclined to put it back into service.

Best of luck with it, John

(since writing this, i see you have modified your post)

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Test it with ESR Meter