Measuring ripple current ability, or a more intelligent way of blowing shit up

[Th3_uN1Qu3]

Today i asked myself this question. How do i measure rated ripple current of a capacitor. Well, since ripple measurements are usually performed at 120Hz, wait a second...

I pulled that old HT subwoofer out of the closet, took the speaker out and hooked it to my cap with my Uni-T UT60E in series. Used Sound Forge to generate a 120Hz sinewave, et voila!

So, what do you exactly need.

• Amplfier that can do at least 50W/4ohm
• TrueRMS AC amp meter
• Caps (obviously)

And if you want to do something useful not just blow shit up:

• Thermocouple or IR thermometer

You hook the cap up to the amplifier with the amp meter in series. You then fire up a sound generator and produce a 120Hz sine wave. Then you increase the volume till the cap starts getting hot.

With the thermocouple you measure ambient temp, then stick it onto the top of the cap. Scotch tape works great but if you have an IR thermometer that's even better. You are then able to plot temperature rise vs ripple current, so next time you recap something, you can make it last forever! Oh and if you have a powerful enough amp, try to see what 5A RMS can do to those little 470u/16v caps.

Bonus: Stick a voltmeter or oscilloscope in parallel with the cap and see how much ripple actually gets thru. Have fun!

[Toasty]

Are you in any commercial flight paths...?







I just wanna note that in case I travel in Europe sometime.....

[Th3_uN1Qu3]

Originally Posted by Toasty

Are you in any commercial flight paths...?

Yup.

[stj]

actually you feed the cap with a 50/50 waveform and scope the output.

then when the waveform starts to look poor you know you found the limit.
*then you blow the can apart!
(i recomend an acrylic box to do it in, i'v had caps explode and it's messy)

[Th3_uN1Qu3]

50/50 meaning square? I know ripple has a sawtooth shape. Though they blow equally well with either sine, saw or square.