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Mains filtering

Discussion in 'General Electronics Discussion' started by stew, Feb 3, 2015.

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  1. stew


    Feb 3, 2015
    Hi Guys, my aim is to build my own mains filter, i know the basics like X type caps for live - neutral,
    and Y type for live / neutral to earth.

    what I would like to know is about the coils round the ferrite rings, obviously the gauge of the wire needs to suit the current being drawn, and if the live is wound clockwise then neutral is wound counterclockwise.

    main question - is there a recommended number of. turns for the coil?
  2. Harald Kapp

    Harald Kapp Moderator Moderator

    Nov 17, 2011
    Welcome to electronicspoint.

    No, there isn't. The coil parameter that is used for dimensioning the mains filter is the inductance. Depending on the form of the core and the type of materila used for the core, different numbers of turns are required to achieve a given inductance. For coils in a mains application you also have to take into account mechanical considerations like creepage and air gap between the two phases or phase and neutral. These are defined by international standards and depend mainly on the working voltage where the coil is being used and the so called overvoltage category, a measure of how much transient voltage above the nominal mains voltage you can expect. You also have to ensure that the wires stay safely in place and do not slip from mechanical stress. You also want to have them wound rather tightly to avoid mains hum from the coil.

    While it is entirely possible to wind your own coil, for this kind of application I recommend using an off the shelf coil from a renowned manfacturer which fullfills the required safety standards. It's good for your health.
    hevans1944 and Arouse1973 like this.
  3. Bluejets


    Oct 5, 2014
    Like this maybe......

    Attached Files:

    Harald Kapp likes this.
  4. Harald Kapp

    Harald Kapp Moderator Moderator

    Nov 17, 2011
    This is perfect.
    Bluejets likes this.
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