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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

    The scope measures the true RMS of the voltage and the current and multiplies to get the power. The waveforms between the generator and the VSD are chopped at 4kHz resulting in an irregular waveform so this is the only way to get a meaningful result. 

    On the grid side, where the meter is, the VSD has to deliver power at a voltage that matches the grid, otherwise it'll go bang. The VSD can control the current exported to the grid so I can see how it is conceivable for this waveform to be irregular. With regards to the 64Hz, I am simply quoting off the datasheet. I would assume for regular sine waves this is OK but when you start introducing irregular waveforms this becomes an issue? 

    The VSD is commissioned for a permanent magnet synchronous motor. The generator nameplate data is all correctly entered into the drive. Siemens have looked at the setup of the drive and have not noticed anything wrong. So the concern is the drive is unsuitable for high efficiency regen export.  

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  • Former Community Member
    0 Former Community Member

    The scope measures the true RMS of the voltage and the current and multiplies to get the power. The waveforms between the generator and the VSD are chopped at 4kHz resulting in an irregular waveform so this is the only way to get a meaningful result. 

    On the grid side, where the meter is, the VSD has to deliver power at a voltage that matches the grid, otherwise it'll go bang. The VSD can control the current exported to the grid so I can see how it is conceivable for this waveform to be irregular. With regards to the 64Hz, I am simply quoting off the datasheet. I would assume for regular sine waves this is OK but when you start introducing irregular waveforms this becomes an issue? 

    The VSD is commissioned for a permanent magnet synchronous motor. The generator nameplate data is all correctly entered into the drive. Siemens have looked at the setup of the drive and have not noticed anything wrong. So the concern is the drive is unsuitable for high efficiency regen export.  

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