Damping coefficient and moment of inertia of PMSM

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Damping coefficient and moment of inertia of PMSM

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xgy_upc
Contributor III

In the mechanical motion equation of PMSM.

Jdw/dt=Te-TL-Bw

How is the value of the moment of inertia "J" obtained ?

How is the value of the damping coefficient "B"obtained?

In Freemaster, the moment of inertia "J" is displayed

figure1.JPG

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3 Replies

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joseftkadlec
NXP Employee
NXP Employee

Hi xgy_upc,

Here are my comments:

  1. From the picture that you shared, I think you are using some older version (> 1 year old) of motor control SW. You can download the latest motor control SW as a part of SDK package for your board here: https://mcuxpresso.nxp.com/
  2. In the latest package there is also a Mechanical Identification which can help you with measurement of these parameters.
  3. J and B parameters are used for speed PI controller coefficients (Kp, Ki) calculation. From our experience it is better to tune these parameters manually because the J and B are usually not accurate (see the Speed controller tuning process in 3PPMSMCKVUG.pdf chapter 11.9 Speed PI controller tuning)
  4. MCAT (FreeMASTER plugin depicted on the picture you shared) can calculate the speed controllers' parameters from mechanical properties of the drive. However, friction B is neglected in the calculation.
  5. I recommend to tune the Speed controller manually.

Have a nice day,

Josef

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xgy_upc
Contributor III

I am using LINIX 45ZWN24-40 provided by NXP. Install the flywheel on the motor shaft as shown below.

IMG_20210119_220719.jpg

So is the load torque zero in the equation of mechanical motion(Jdw/dt=Te-TL-Bw)?

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135 Views
MichalH
NXP Employee
NXP Employee

Dear user,

I'm sorry the Motor Control technology is out of scope of the FreeMASTER forum. Even if the Motor Control user interface is hosted in FreeMASTER, your question is beyond of our expertise. I'm going to move your question to Motor Control and Smart Energy forum.

A general comment on your question, FreeMASTER hosts the HTML+JavaScript application - which is a user readable code. You should be able to find the answer in the source code. 

Best regards,
Michal

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