Ld and Lq measurement

tim960622 — Thu, 01 Nov 2018 16:43:36 GMT

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?

Re: Ld and Lq measurement

Daniel_Popa — Mon, 12 Nov 2018 13:25:04 GMT

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

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Ld and Lq measurement

Re: Ld and Lq measurement