I am working on a permanent magnet synchronous motor, and try something about vector control. When I try to build the mathematic model for such motor in dq frame, I come across a problem that confuses me. In the motor dq model, I need to find out the values of Lq and Ld, while I can't get from the motor specifics (I have got some formula to calculate Lm and Ld, but it still need some variables that I can't get from the motor specifics). Usually, how to identify such values in dq motor model?

 

I was doing the same thing about a year ago and could not find a way to get the dq inductances from the given manufacturer parameters. I tried modelling the three phase like 3 separate DC motors with some success but started working on implementation before finisheing the model. I am also working on vector control of a pmsm using a TI DSP. In need of some help with getting the current loops stable. email is "[email protected]", mailto:[email protected]

 

The direct-axis and quadrature-axis inductances are (L1+Lm) and (L2+Lm) respectively. Of course, L1 and L2 are derived from the stator and rotor
(referred to stator) reactances, respectively.

Regards,
Phil Corso, PE
(Boca Raton, FL)

 

Re my Fri, Sep 20, 9:32 pm, comment to Tao Yang:

A very big OOPS (the most feared word in an operating room)! I apologize for submitting the wrong data. I supplied data for an induction motor.

For a permanent-magnet synchronous motor, the Ld and Lq inductance values can be derived from their associated Xd and Xq reactances. These
values are available from construction of the terminal voltage phasor equation for a cylindrical-rotor synchronous motor.

Such a construction is shown in the following reference:

Title: Electric Machinery
Authors: A.E. Fitzgerald & C. Kingsley
Publisher: McGraw-Hill
ISBN: 61-10131

If representative or typical data is useful to you, send me your Fax No.

Regards,
Phil Corso, PE
(Boca Raton, FL)

 

Don’t worry about that, Phil,

So far I have some formulas that could deduce the values of Lq and Ld, but it need some parameters that I can’t find in the motor menu.(Lls, L0s, and L2s: the leakage inductance , constant self stator phase inductance and the second order harmonic inductance).

The formula can be found in the book: “Vector Control and Dynamics of AC”. D.W. Novotny.

Thanks,
Tao

 

Tao:
I'm not sure from your reply that you have the
solution or that you still need one. If the former, then, ignore this message. If the latter, then, L1, L2, and L0 represent positive,
negative, and zero sequence inductances, respectively, as determined by the theory of "Symmetrical Components".

The subject is covered in the book "Symmetrical Components" by Wagner and Evens", McGraw-Hill, 1933. It provides calculation formulas as well
as test procedures to determine the three components.

If you need additional info, please contact me.

Regards,
Phil Corso, PE
(Boca Raton, FL)

 

Phil,

just read your comments on the dq reference frame problems that another member had and hoped you might be able to help me. Im working on a Masters project and am having some trouble grasping the concept of the dq reference frame and its use in control of electrical machines. I would greatly appreciate and help you can give or any recommended texts, websites etc.

Please feel free to email me directly at [email protected].

Thankyou and I look forward to hearing from you soon,

David Sutton

 

I am designing a DTC based control system for speed control of induction motor. I need to know the mathematical model used in direct torque control (DTC) as well as the method used to select the switching table of the torque and the stator flux.

 

The Alist

If you would like some documents of induction motor torque control, I will send them to you if you provide your email address.

Regards
George Younkin
gwyounkin [at] charter.net