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Regenerative Drives - Effect of Power Factor

Former Community Member
Former Community Member

I am working on a small 16kW hydro system which is experiencing about 15% loss in the Regenerative VSD. To maximise efficiency the turbine operates at variable speed. The VSD controls a synchronous generator and supplies the grid.

The VSD is a Siemens G120. The datasheet states that the efficiency should be around 96%, whilst also stating that the Power Factor is 0.9. I am looking to replace this drive for an ABB ACS 880-11 which has similar efficiency but a unity power factor.

Firstly can I trust these datasheets since, I assume, they relate to the VSD delivering electrical energy to a motor rather receiving it from a generator? Is there an efficiency penalty for regenerative generation?

Secondly, with all else being equal, will the drive with a unity power factor equate to more electrical energy on the meter than the drive with a 0.9 power factor? 

Thanks

 

 

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  • Former Community Member
    0 Former Community Member

    Hi Adrian

    Thanks for your reply

    We have measured the output from the generator with an Oscilloscope which provides the power into the VSD. The power exported to the grid is measured on a meter installed in the control cabinet, next to the VSD. The difference between the two readings is about 2kW. Sadly we didn't put the scope on the output terminals from the VSD so we only have the meter values, although there is no reason to suggest they are wrong. 

    Separately to this, we have connected the generator up to a resistive load bank to confirm the power measurement; this measurement agrees with the values measured on the scope with the VSD in circuit.

    What is strange is that this 2kW can't be felt as heat in the cabinet, or at least it is not obvious.   

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  • Former Community Member
    0 Former Community Member

    Hi Adrian

    Thanks for your reply

    We have measured the output from the generator with an Oscilloscope which provides the power into the VSD. The power exported to the grid is measured on a meter installed in the control cabinet, next to the VSD. The difference between the two readings is about 2kW. Sadly we didn't put the scope on the output terminals from the VSD so we only have the meter values, although there is no reason to suggest they are wrong. 

    Separately to this, we have connected the generator up to a resistive load bank to confirm the power measurement; this measurement agrees with the values measured on the scope with the VSD in circuit.

    What is strange is that this 2kW can't be felt as heat in the cabinet, or at least it is not obvious.   

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