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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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    A note to Adrian.

    Using an induction motor will generate power, but you need to consider the rotor cage loss and therefore the efficiency. Your equations will need a significant level of “calibration values” to correctly read the true dyno power, and you might find it easier to measure the speed and torque directly, and just use the motor as a brake. You can measure the torque with no moving parts by mounting the motor on load cells and measuring the difference between the two sides under load. Rotation speed is easy!

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  • 0

    A note to Adrian.

    Using an induction motor will generate power, but you need to consider the rotor cage loss and therefore the efficiency. Your equations will need a significant level of “calibration values” to correctly read the true dyno power, and you might find it easier to measure the speed and torque directly, and just use the motor as a brake. You can measure the torque with no moving parts by mounting the motor on load cells and measuring the difference between the two sides under load. Rotation speed is easy!

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