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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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    I think Mike is on the right lines - the regen output from the VSD is likely to be far from sinusoidal. Unless the metering equipment is capable of true rms reading then its unlikely to give the correct answer.

    So are you saying you are comparing the output of the generator (what kind of machine?) with the output of the VSD? Depending on the kind of motor/generator you are using, where is the excitation coming from? If its an AC machine, the VSD still has excite the motor to make it generate. This may be confusing you measurements of the real generator output when connected to the VSD?

    Does the VSD itself tell you the regen output? Some do, others are not so helpful.

    I'm having a similar problem with the design of an engine test dyno. The brief wants to use an AC induction motor as the dyno and dump the energy recovered as the dyno brakes the engine back onto the mains. The doing it is easy, its getting the instrumentation right that's the problem (this is for an educational environment so the numbers need to stack up in an energy balance equation…. fuel+air > mechanical + heat + noise > regen electrical etc)

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  • 0

    I think Mike is on the right lines - the regen output from the VSD is likely to be far from sinusoidal. Unless the metering equipment is capable of true rms reading then its unlikely to give the correct answer.

    So are you saying you are comparing the output of the generator (what kind of machine?) with the output of the VSD? Depending on the kind of motor/generator you are using, where is the excitation coming from? If its an AC machine, the VSD still has excite the motor to make it generate. This may be confusing you measurements of the real generator output when connected to the VSD?

    Does the VSD itself tell you the regen output? Some do, others are not so helpful.

    I'm having a similar problem with the design of an engine test dyno. The brief wants to use an AC induction motor as the dyno and dump the energy recovered as the dyno brakes the engine back onto the mains. The doing it is easy, its getting the instrumentation right that's the problem (this is for an educational environment so the numbers need to stack up in an energy balance equation…. fuel+air > mechanical + heat + noise > regen electrical etc)

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