Capacitor Lifetime Testing

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  • onders
    New Member
    • Oct 2006
    • 6

    #1

    Capacitor Lifetime Testing

    Hi you all.

    I am trying to setup a suitable circuit that applies the desired max ripple current to a capacitor which also has the rated DC voltage accross it so that I could realize the lifetime test.

    May anoybody help me what kind of circuit to use and the necessary formulas?

    Thanks...
  • willawake
    Super Modulator
    • Nov 2003
    • 8457
    • Greece

    #2
    Re: Capacitor Lifetime Testing

    i would be interested in that also.
    capacitor lab yachtmati techmati

    Comment

    • yanz
      Badcaps Veteran
      • Nov 2004
      • 910

      #3
      Re: Capacitor Lifetime Testing

      im waiting for some gurus to arrive here and give some advice..
      days are so short when you actually do something..

      Comment

      • davmax
        Badcaps Veteran
        • Dec 2005
        • 899

        #4
        Re: Capacitor Lifetime Testing

        The request to make this cap setup is not too easy. It depends on the type of caps and their value.

        Example. Some can take 3.2 amps (Samxon 3300u 6.3V). To add this level of current into 9 milliohm requires an rms voltage of only 28mV. This represents quite a small power of 90 milliwatts. So what is required to produce the 100Khz ripple is a signal generator capable of delivering the power then a high frequency transformer to reduce the voltage down to about 30mV @ 3.2 amps.

        The cap on test must be connected to a DC power supply that has an inductor to block 100Khz power from entering the power supply. The 100Khz output from the signal gen via the special transformer must be fed to the cap on test through a capacitor rated to take the high current ripple. The DC voltage is set to the required level. ALL QUITE A CHALLENGE.
        Gigabyte EP45-DS3L Ultra Reliable (Power saver)
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        160Gb WD eSATAII Server grade for backup.
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        Comment

        • PeteS in CA
          Badcaps Legend
          • Aug 2005
          • 3579
          • USA, Unsure of Planet

          #5
          Re: Capacitor Lifetime Testing

          Major cap vendors such as UCC use a sine-wave-oscillator-amplifier instrument that costs a couple of kilobucks in a temperature-controlled environment. A more rudimentary approach, based on dav's comments above would be to use a square wave instead of a sine wave - a square wave is easier to produce - a 50% duty-cycle inverter and a step-down (voltage) transformer of suitable turns ratio. The remaining issue (on which I cannot comment further) is controlling the load current. BTW, when caps get warm or hot, their C increases and their Z decreases, both significantly.
          PeteS in CA

          Power Supplies should be boring: No loud noises, no bright flashes, and no bad smells.
          ****************************
          To kill personal responsibility, initiative or success, punish it by taxing it. To encourage irresponsibility, improvidence, dependence and failure, reward it by subsidizing it.
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          Comment

          • onders
            New Member
            • Oct 2006
            • 6

            #6
            Re: Capacitor Lifetime Testing

            Hi davmax,
            Thank you very much.
            Is it possible for you to send a basic schematic of the test circuit you suggest?
            Will be very happy upon your help.
            Thanks.

            The request to make this cap setup is not too easy. It depends on the type of caps and their value.

            Example. Some can take 3.2 amps (Samxon 3300u 6.3V). To add this level of current into 9 milliohm requires an rms voltage of only 28mV. This represents quite a small power of 90 milliwatts. So what is required to produce the 100Khz ripple is a signal generator capable of delivering the power then a high frequency transformer to reduce the voltage down to about 30mV @ 3.2 amps.

            The cap on test must be connected to a DC power supply that has an inductor to block 100Khz power from entering the power supply. The 100Khz output from the signal gen via the special transformer must be fed to the cap on test through a capacitor rated to take the high current ripple. The DC voltage is set to the required level. ALL QUITE A CHALLENGE.

            Comment

            • davmax
              Badcaps Veteran
              • Dec 2005
              • 899

              #7
              Re: Capacitor Lifetime Testing

              I have put together a sketch diagram of the principle. You would need some test equipment to actually measure the level of ripple in the test capacitor. One method is to insert a low value resistor (50 to 100 milliohm) at the output of the step down transformer and measure the 100Khz voltage across it. But this would change the transformer design and increase the power requirement of the signal generator. The 100Khz signal output must be adjustable from 0 to 5 Vrms.
              Attached Files
              Last edited by davmax; 11-09-2006, 07:28 PM.
              Gigabyte EP45-DS3L Ultra Reliable (Power saver)
              Intel E8400 (3000Mhz) Bios temps. 4096Mb 800Mhz DDR2 Corsair XMS2 4-4-4-12
              160Gb WD SATAII Server grade
              Nvidia 8500GT 256Mb
              160Gb WD eSATAII Server grade for backup.
              Samsung 18x DVD writer
              Pioneer 16x DVD writer + 6x Dual layer
              33 way card reader
              Windows XP Pro SP3
              Thermaltake Matrix case with 430W Silent Power
              17" Benq FP737s LCD monitor
              HP Officejet Pro K5300 with refillable tanks

              Comment

              • davmax
                Badcaps Veteran
                • Dec 2005
                • 899

                #8
                Re: Capacitor Lifetime Testing

                I have put a bit more time into a test rig. Getting it to a workable state. See the attachment. Note the 16 ohm 10W resistor is to ensure the amplifier sees some resistive load, depending on the amplifier it still might not like the capacitive load of C1, capacitive loads can cause oscillation. NOTE the turns ratio of the transformer is incorrect on the diagram it should read 7:1 (The 45:1 represents the impedance ratio i.e the Xc of C1 = 0.33 is seen by the amp as in the region of 45 x 0.33 = 15 ohm.).

                The current through the device under test (DUT) can be measured across C1 at 0.33volts/ amp, this holds only for 100Khz.
                Attached Files
                Gigabyte EP45-DS3L Ultra Reliable (Power saver)
                Intel E8400 (3000Mhz) Bios temps. 4096Mb 800Mhz DDR2 Corsair XMS2 4-4-4-12
                160Gb WD SATAII Server grade
                Nvidia 8500GT 256Mb
                160Gb WD eSATAII Server grade for backup.
                Samsung 18x DVD writer
                Pioneer 16x DVD writer + 6x Dual layer
                33 way card reader
                Windows XP Pro SP3
                Thermaltake Matrix case with 430W Silent Power
                17" Benq FP737s LCD monitor
                HP Officejet Pro K5300 with refillable tanks

                Comment

                • onders
                  New Member
                  • Oct 2006
                  • 6

                  #9
                  Re: Capacitor Lifetime Testing

                  Hi again Davmax,
                  Thanks for the schematics.
                  C1 and the inductor are used to prevent dc and ac voltages to pass accross the sources, is this true?
                  Also, as I see, most of the datasheets give the ripple current at 120Hz, not 100kHz, is this scheme directly convertable to 120Hz version?
                  With this rig is it possible to apply ripple currents in the range from 50mA to 3000mA or so while applying dc voltages from 10VDC to 450VDC?
                  Thank you very much,
                  Regards...

                  Comment

                  • arneson
                    Badcaps Legend
                    • Sep 2005
                    • 1267

                    #10
                    Re: Capacitor Lifetime Testing

                    I posted an old cap analyser that should perform this function in a piece of test equipment.
                    It's in the for sale section, it will quick charge caps at different frequencies and voltages, recondition caps and measure resistance of cap.
                    Jim

                    Comment

                    • onders
                      New Member
                      • Oct 2006
                      • 6

                      #11
                      Re: Capacitor Lifetime Testing

                      Thank you arneson,
                      Here there is a bigger picture of your device.

                      http://imagehost.vendio.com/bin/view...2e4-e19a4&sp=1

                      Also it is said to be 33$ here:
                      http://cgi.ebay.com/Pyramid-CRA-2-El...ayphotohosting

                      And also, looking its properties, it is not suitable for serios lifetime tests I think. It is just to decide for bad caps...

                      Thank you.

                      Comment

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