Torque Tolerance of a FOC VFD

[Phaneas]

Hello,

we try to optimize the parameter set of a 2.2 MW Drive with field oriented control. We try to get the best result between reference torque of the control and actual torque measured at the motor shaft. We have tolerances depending of motor speed and amplitude of the torque of around +/- 10%.

Has anybody a idee or a document how high are the standard tolerance between Actual Torque and Reference Torque of VFD's?

Thanks in advance

 

[Phaneas]

come on, any comments please!

 

[DickDV]

Phaneas, there are a good number of us on this BBS that are interested in being helpful but you are dealing with 2.2MW and Medium Voltage which cuts down the number of people that are knowledgeable drastically. Or, to say it another way, your question is highly specialized.

Most participants in this forum go way out of their way to avoid providing irresponsible or simply erroneous answers so, if no one has responded, I would conclude that we can't offer you a good solid trustworthy answer.

Sorry.

 

[jraef]

In that realm, the only people qualified to answer that question will be the ones who engineered the VFD you are using / planning to use. There are no "performance standards" to which all MV VFDs are built, the design approaches to how they atain their performance are typically very closely guarded sectrets because they represent massive amounts of R&D expenditure.

Who are you considering? I would be talking to Siemens, ABB, maybe GE if you are in the US, Toshiba if not (same product).


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[ozmosis]

What's a FOC VFD? (Free Of Charge?)

 

[DickDV]

ozmosis, FOC stands for Field Oriented Control. I have yet to get a cogent explanation of the differences between it and sensorless vector. Or, DTC, or Flux Vector, for that matter.

Anybody aware of a reasonably well-written white paper making these comparisons?

 

[Phaneas]

Thanks for the replies, but the developer does not have really an answer at the question, because that's the difference about theoretical calculation and reality. And there is not much experience with that large drives.
I talked to another developer and he had measured a Danfoss VFD. He compared actual Power at the shaft with the active Power value of the Inverter and in the nominal point of the machine it was 5% acurate, but on other points it was up to 20% wrong. That was 35kW Inverter