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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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    Ah sorry, should have used the mechanical one - the reactive energy is like the energy stored in the flywheel, built up over many cycles and topping up on each explosion and running down a bit in between. In a well running system you do not intend to get all of the energy out of the flywheel at once- if you did it  would come to a dead stop, indeed once running smoothly the level of energy stored in the flywheel is cyclostationary - If you prefer not to use the mathematical shorthand, that means at the same point in the next cycle, it will be back to exactly the same state- so there is no overall gain or loss to the flywheel over a whole cycle, just short term borrowing and paying back at different phases in the cycle. This is not energy you can use without stopping it working.

    Mike.

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  • 0

    Ah sorry, should have used the mechanical one - the reactive energy is like the energy stored in the flywheel, built up over many cycles and topping up on each explosion and running down a bit in between. In a well running system you do not intend to get all of the energy out of the flywheel at once- if you did it  would come to a dead stop, indeed once running smoothly the level of energy stored in the flywheel is cyclostationary - If you prefer not to use the mathematical shorthand, that means at the same point in the next cycle, it will be back to exactly the same state- so there is no overall gain or loss to the flywheel over a whole cycle, just short term borrowing and paying back at different phases in the cycle. This is not energy you can use without stopping it working.

    Mike.

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