Ld and Lq measurement

[tim960622]

I have read the application note of "PMSM Electrical Parameters Measurement".I'm confused about the equation of inductance measurement at equation 9 and 10.

The total inductance for serial-parallel of the stator winding  L will be 3/2 L-theta(electrical theta)?is L-theta the phase inductance? 

so when the electrical angle of rotor is at 0 degree, Ld will be (2/3)L = (2/3)*(3/2)L-theta = L-theta and so does Lq at the 90 degree?

[dumitru-daniel_]

Hello,

To measure the Ld and Lq you need to measure the L (total inductance) between phase A in serie with Phase B and Phase C

 To do that, you need to measure the current flowing thru phase A in 2 different situations:

- d-axis aligned with phase A (this is easy since the rotor tends to align naturally when the A-phase is magnetized)

- q-axis aligned with phase A (this will be harder since you need to lock the rotor mechanically to maintained the alignment)

Once you measure the current waveform for the both cases you can obtain the L value using the raising time and known phase resistance

Only then, using the eq 9 and 10 you will be able to compute the Ld/Lq

Hope this helps!

Daniel