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Measuring the rectifier output voltage

Discussion in 'Electronic Design' started by [email protected], Nov 3, 2008.

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  1. Guest

    I my plant we have a rectifier for electrolytic cleaning. 7500A and
    30V(Max). We give the reference for current. The problem is when we
    measure the current through out PLC analog channel we find it
    fluctuating. The current waveform exactly follows the voltage
    waveform. The configuration is 2 half wave 3-phase rectifiers working
    in paralle through the interphase transformer. Should I add something
    to get an steady feedback. I suspect the fluctuation has to do with
    the scanning of the AI channel of the PLC. we should send the coltage
    as DC without harmonics rather than the way it is now.
  2. legg

    legg Guest

    Filter the measurement or synchronize it to the phase period.

  3. Mark

    Mark Guest

    Does the "rectifier" have any filtering?

    If not, what you are seeing is correct.

    The current waveform will follow the voltage waveform.

    But for your application, it probably doesn't matter, what counts is
    the AVERAGE current. So you can read the average current with a meter
    or matematically figure the average current value of your waveform.

  4. What is the output of your current sensor? If it's something like
    0-10V you may be able to add a simple low-pass filter to give you
    average current, and, if necessary, fiddle the value a bit to get it
    to agree with the instrumentation on your baths. If it's a 5A CT you
    may have to add signal conditioning ahead of the PLC analog inputs.

    Best regards,
    Spehro Pefhany
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