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Model of EMC Conducted Emission Test Reciever - Quasi peak measurements

Discussion in 'Electronic Design' started by Klaus Vestergaard Kragelund, May 24, 2005.

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  1. Hi

    I'm playing with using pseudo random PWM on a motor drive to minimize
    the conducted emission level of the inverter

    For that purpose I'm testing a system using a standard Rhode&Swartz test
    reciever with the following frequency band 150kHz to 30MHz (9kHz
    bandwidth, 5kHz step and both average and quasi peak measurements)

    The PWM converter clock is running at 18kHz and modulated +/-20% at
    100Hz rate (in the beginning triagular shaped mdulation)

    But the measurements take a long time - do anyone know how to model the
    input of the quasi peak detector to mimic the result seen on the test
    reciever? If I get a model I can run some simulations instead.

    As far as I know the quasi-peak detector consists of a rectifying diode
    in series with a RC filter and a load resistor on the output of that
    filer (shorter rise time than fall time to transients)


  2. Mark

    Mark Guest

    Randomizing the frequency does not reduce the emissions, it just
    spreads them out so that you can pass the test. But it still creates
    nearly the same level of interference and to more frequencies. I know
    this has become a popular technique to pass EMI tests but I think it is
    a bad idea and just HIDES the problem.

  3. Paul Burke

    Paul Burke Guest

    The EMC standards are a hoop to jump through, not an objective quality
    standard. They say meet this curve: you meet this curve, you've passed.
    Don't start inventing extra obstacles, there are plenty of stupid,
    unnecessary ones already. RoHS/WEE anyone?

    Paul Burke
  4. Terry Given

    Terry Given Guest

    This is true, *but* passing the test is a necessary requirement. That
    the test is less than useful is a whole 'nother can of worms.

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