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Line filter question

  1. Oct 18, 2007 #1
    I am trying to build the Schaffner line filter FN410 out of discrete parts. The datasheet for that part can be seen here:

    http://www.schaffner.com/corporate/...om/components/en/_pdf/Datasheet+FN410+e+6.pdf

    Anyways, they list all the values for the inductors and capacitors that they use in the circuit except for the inductors connected to ground. I believe they help against incoming common-mode noise. Does anybody have an idea what inductance should be use for those inductors?

    Thanks in advance!
     
  2. jcsd
  3. Oct 18, 2007 #2

    berkeman

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    Staff: Mentor

    Welcome to the PF, Kilamir. It's a great place.

    I don't see any inductors to ground in the filter datasheet schematic, and inductors are not usually connected to ground in this type of filter anyway. In general, the topology will be some series high impedances (the inductors) and some parallel low impedances (the X and Y capacitors) to provide the lowpass filtering characteristics (for both common mode and differential mode).

    In the schematic for this filter, there is an X cap for the differential lowpass filter characteristic (in conjunction with the inductors), and two Y caps for the common-mode lowpass filter characteristic. Of course, the Y caps also provide some additional differential LPF contribution as well (Quiz Question -- why?). Does that help?
     
    Last edited: Oct 18, 2007
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