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  1. #1
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    What is output voltage of 3 phase vfd

    Hello

    I have question regarding VFD. What is output voltage of 3 phase vfd (input 400v).
    And what is out voltage for single phase 220v to single phase vfd for PSC motor.

    In 3 phase vfd phase angle difference between each phase is 120 degree and in case of single phase vfd for Psc Is 90drgree from each phase.
    Thanks

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    Re: What is output voltage of 3 phase vfd

    Maximum output voltage of regular 3-phase inverter is equal to input voltage.

    I'm not aware of any industrial inverter designed for PSC motor operation. If you design it however, you have to consider the possible different voltage range of capacitor winding. For 90 degree phase and symmetrical output, the available voltage is only 155 volt with 220 volt input.



    •   Alt17th May 2018, 21:36

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  3. #3
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    Re: What is output voltage of 3 phase vfd

    I am working on it for running 3ph induction motor input voltage 220v
    For 1ph to 3ph my maximum output voltage is 187vac phase to phase i.e 325/√3 my i was expecting 220v.

    For psc Motor where phase difference is 90degree my out put voltage U (0degree) V(180degree) W(90degree)
    Voltage between U-V=200v
    V-W=145v
    U-W=145v

    Is it right any suggestion
    How phase difference casue of voltage difference



    •   Alt19th May 2018, 05:08

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    Re: What is output voltage of 3 phase vfd

    For 1ph to 3ph my maximum output voltage is 187vac phase to phase i.e 325/√3 my i was expecting 220v.
    Wrong modulation method. This happens if you output only a three phase sine voltage. You need to superimpose a zero sequence (common mode) component to get maximal output voltage with the available DC bus voltage. It's done in any industrial VFD.


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    •   Alt19th May 2018, 08:36

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    Re: What is output voltage of 3 phase vfd

    thats good to read. but i do not know about that modulation technique.
    can you support me how i can implement it. so that i can utilize maximum dc bus



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    Re: What is output voltage of 3 phase vfd

    Code C - [expand]
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    int uvw[3];
    int a_uvw[3];
    int sym;
     
    for (i=0;i<3;i++)
      a_uvw[i] = abs(uvw[i]);
    if (a_uvw[1] > a_uvw[2])
      if (a_uvw[2] > a_uvw[3])
        symm = uvw[3];
      else
        symm = uvw[2];
    else if (a_uvw[1] > a_uvw[3])
        symm = uvw[3];
    else
        symm = uvw[1];
    symm = symm/2;
    for (i=0;i<3;i++)
      uvw[i] += symm;


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    Re: What is output voltage of 3 phase vfd

    i understand little about code but still unable to implement. can you elaborate more



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    Re: What is output voltage of 3 phase vfd

    On input, uvw is the three phase sine voltage vector. It's modified by a zero sequence which is half of the smallest instantaneous value to get a centered sine space vector.

    Click image for larger version. 

Name:	centered.PNG 
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ID:	146734


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    •   Alt19th May 2018, 14:07

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  9. #9
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    Re: What is output voltage of 3 phase vfd

    I think this modulation technique is space vector right.
    I am following v/f spwm technique.
    What will be output voltage for 220vac.



  10. #10
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    Re: What is output voltage of 3 phase vfd

    That makes no difference.



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