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  1. #1
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    Def-Stan 59-411 proble with MOVs don't dissipate energy

    Hi All,

    Anyone has experience with this clause of the Def-Stan 59-411 part 3.

    We have tried to pass a couple of times. We have place a couple of MOV in the input stage and they don't dissipate the energy completely and there is always some damage. Is there any other method that we could applied?

    This is the close of the standard and a link to consult:

    DCS12 – Sea. Low freq. transient

    B.13 DCS12.B Imported Low Frequency Transient Susceptibility Power Lines (Sea
    Services)

    http://emc.jaguarlandrover.com.edges...0Equipment.pdf


    thanks a lot,
    Winsu

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    Re: Def-Stan 59-411 proble with MOVs don't dissipate energy

    We have place a couple of MOV in the input stage and they don't dissipate the energy completely and there is always some damage.
    I wonder if the used MOV are actually rated for the applied DCS12 test signals, which are considerably different from industry standard surge test signals.

    But if the MOV survives, the problem is most likely about too high hope in the capability of MOV voltage clamping. Did you read the datasheet thoroughly and calculate the expectable clamping voltage in your test? For a closer view at the problem, you should surely show a schematic of the input circuit under test and report where the damage occurs.



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  3. #3
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    Re: Def-Stan 59-411 proble with MOVs don't dissipate energy

    Unfortunately the test were done before my time, I don't know what components were damaged. I do know that the MOVs survived. The MOVs are located right after a line filter. Something like this:


    Click image for larger version. 

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    I' am know thinking to put two gas arrester between L-Earth and N-earth to improve energy absorption. I have read that gas arrester are slower than MOVs but they can manage more energy than MOVs. The idea is to put the MOVs after the filter ( as they are know), then when the MOVs clamp there will be some voltage dropping in the differential coils to allow that the gas arresters clamp and **** most of the energy. I got the idea from this PDF:

    https://m.littelfuse.com/~/media/ele...ubes/ec640.pdf



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