Capacitor ESR Measurements

[XgamerGt03]

So I got around to taking some caps in to work today to look at during lunch. We have a cap meter there that is used to measure leakage current and is pretty good for reforming caps so I use it quite a lot.

I currently have two Sprague Atom 40uF 450V caps and three Sprague Atom 8uF 450V caps. I'm planning on getting a number of others to test in this same set up. While some of the results are a bit different than what the manufacturer may use to spec the parts I should be able to get a good idea of how they compare with each other.

So here are my results for the five caps I have.

Cap 1: Name Plate Rating: 40 uF Actual: 48.6 uF Lekage Current: 120uA
ESR: 1.637 ohms Reactance: - 3.716ohms Inductance: .59 mH Impedance: 4.07 ohms
Phase Angle: -66.02 degrees DF: .44


Cap 2: Name Plate Rating: 40 uF Actual: 49 uF Lekage Current: 10uA
ESR: 1.779 ohms Reactance: - 3.668ohms Inductance: .58 mH Impedance: 3.99 ohms
Phase Angle: -66.77 degrees DF: .48


Cap 3: Name Plate Rating: 8 uF Actual: 7.62 uF Lekage Current: 0uA
ESR: 5.37 ohms Reactance: - 22.43 ohms Inductance: 3.55 mH
Impedance: 23.12 ohms Phase Angle: -76.21 degrees DF: .23

Cap 4: Name Plate Rating: 8 uF Actual: 7.66 uF Lekage Current: 0uA
ESR: 5.68 ohms Reactance: - 22.38 ohms Inductance: 3.47 mH
Impedance: 23.06 ohms Phase Angle: -75.96 degrees DF: .25

Cap 5: Name Plate Rating: 8 uF Actual: 7.72 uF Lekage Current: 0uA
ESR: 5.45 ohms Reactance: - 22.03 ohms Inductance: 3.50 mH
Impedance: 22.69 ohms Phase Angle: -76.17 degrees DF: .24

Where the Leakage current shows 0 I wasn't able to get any reading with the meter. All caps were put on the tester for 8 hours each, and were all new.

Capacitance and Leakage current was measured with a Sorensen LCR meter. All others were measured using an Agilent 4338B milliohm meter. Test frequency for the 4338B is 1kHz and a 10mA peak AC signal.

So what we do find out is that the critical frequency of all of these is right about 1Khz. Above that the cap will act more like an inductor than a capacitor.

[selloutrr]

If your tests are correct based on the leakage test results caps 1 and 2 are bad. I would question using them in a build.

[XgamerGt03]

If your tests are correct based on the leakage test results caps 1 and 2 are bad. I would question using them in a build.

Cap 1 is most likely bad. I'm planning on taking it back in and letting it sit on the test again for another 8 hours tomorrow to see if it is any better.

Cap 2 is in an allowable range. About 40uA max is what i would allow for that cap. The 10uA could also be in the range of 5-10uA. It doesn't work that well between 0-10uA for readings.... but for what I want it usually works.

I usually go with something like (.002 * V * C) for maximum allowable leakage current. It is usually better than what the manufacturers specify.

[diagrammatiks]

hey when's the next time you are going in to test some stuff.

you want more stuffs?

[XgamerGt03]

hey when's the next time you are going in to test some stuff.

you want more stuffs?

When I have stuff to test I'll test more. I can use the meters anytime at work since they sit at my work desk.

I'm looking at getting some of the film caps like Solens versus a few of the other brands out there to get some ideas about the differences. F&T, Nichicon, JJ, and a few others. The film caps are likely to have ESR's even lower than what I read here.

[diagrammatiks]

hey when's the next time you are going in to test some stuff.

you want more stuffs?

When I have stuff to test I'll test more. I can use the meters anytime at work since they sit at my work desk.

I'm looking at getting some of the film caps like Solens versus a few of the other brands out there to get some ideas about the differences. F&T, Nichicon, JJ, and a few others. The film caps are likely to have ESR's even lower than what I read here.

I doubt the film caps will hit double digit milliohms.

Anyhow I've got some stuffs. you know how to reach me.

I've got solens, f & t, nichicon, rifa, epcos, philips, panasonic, should have some aerovox bhc coming in soon.

Wanna test some of my motor runs for me?