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  1. #21
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    Re: Bias current sensor for floating earth

    Please find attached again the LTspice file. I hope now is ok.
    Don't think so. U1 LED is driven with wrong polarity and has negative transistor supply.

    Click image for larger version. 

Name:	bad_imd.PNG 
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ID:	157827

    Many previously mentioned problems are still present, ignoring balanced ground fault, huge circuit power dissipation, about kV voltage drop at current limiting transistors.

    I have to be in compliance with the IEC 61557-8. But I will ask to the standards department to be sure.
    Please check particularly sub clauses 4.1 General requirements and 4.2 Types of IMDs.



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  2. #22
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    Re: Bias current sensor for floating earth

    Quote Originally Posted by FvM View Post
    Don't think so. U1 LED is driven with wrong polarity and has negative transistor supply.

    Click image for larger version. 

Name:	bad_imd.PNG 
Views:	2 
Size:	20.0 KB 
ID:	157827

    Many previously mentioned problems are still present, ignoring balanced ground fault, huge circuit power dissipation, about kV voltage drop at current limiting transistors.


    Please check particularly sub clauses 4.1 General requirements and 4.2 Types of IMDs.
    According to standars department, it is NOT necessary to be in compliance with the IEC 61557-8.

    On the other hand, the last design is not working properly, So I will say that the best idea I have right now in order to solve the earth fault issue is the first one. I mean the next attached simulation schematic.

    ISS.txt

    Of course it has very high current leakages y and other issues. But maybe someone in the forum can help me to improve it. I am open to all the comments.

    Thanks in advance.



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