Rules and Guidelines
Want to participate in the discussions? Please read our Community Rules and Guidelines. Need some help? Visit Support and Answers.

  • State Not Answered
  • Locked Locked
  • Replies 23 replies
  • Subscribers 32 subscribers
  • Views 2866 views
  • Users 0 members are here
Options
You may also be interested in
This discussion is locked.
You cannot post a reply to this discussion. If you have a question start a new discussion

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

 

 

Parents
  • Former Community Member
    0 Former Community Member
    I think I should clarify that since the voltage waveforms from the generator to the VSD are chopped, the power has been calculated my multiplying the voltage with the current at each instance in time and averaging aver a given number of current waveforms (since they are sinusoidal). While RMS values are calculated they aren't particularly useful. The scope has recorded data at a a frequency of 1e7 samples per second so I am confident with the result. 


    However without repeating the measurement on the meter terminals I can't be sure what the reactive power is and I only have the True Power available to me. The datasheet suggest for our drive the power factor is 0.9. If this is the case there is 10% of the apparent power which isn't being converted into useful True Power which is what I want to maximise. 


    If the 2kW is not being lost as heat (since we can't feel it) then surely there is reactive power at the meter. 


    It does appear that changing the drive to one specifically designed for efficient regenerative operation could resolve this but not before measuring the waveforms on the meter terminals.
Reply
  • Former Community Member
    0 Former Community Member
    I think I should clarify that since the voltage waveforms from the generator to the VSD are chopped, the power has been calculated my multiplying the voltage with the current at each instance in time and averaging aver a given number of current waveforms (since they are sinusoidal). While RMS values are calculated they aren't particularly useful. The scope has recorded data at a a frequency of 1e7 samples per second so I am confident with the result. 


    However without repeating the measurement on the meter terminals I can't be sure what the reactive power is and I only have the True Power available to me. The datasheet suggest for our drive the power factor is 0.9. If this is the case there is 10% of the apparent power which isn't being converted into useful True Power which is what I want to maximise. 


    If the 2kW is not being lost as heat (since we can't feel it) then surely there is reactive power at the meter. 


    It does appear that changing the drive to one specifically designed for efficient regenerative operation could resolve this but not before measuring the waveforms on the meter terminals.
Children
No Data

Join us to get the best from IET EngX.

Joining EngX lets you personalise your experience so you stay up to date on the topics that interest you, plus you’ll be able to make connections who are looking to collaborate, exchange ideas and more.

Join us Not now

Community Rules & Guidelines