Hi.
I'm driving a PMSM with FOC (Workbench file attached for reference) with MCSDK 6.3.0 in torque mode.
Main parameters:
- 1400 Hz electrical frequency max -- therefore 16 kHz PWM
- 100 Hz mechanical frequency max
- ~0.03 mH line-to-line inductance
- ~9 V/Hz Kv
- 0.1 Ohm winding resistance
- up to 20 A torque sustained
- around 48 V input
With the default settings of OCP -- 45 Apk and 47.06 ns filter -- OCP is reliably triggered when Iq reference goes above about 7.5 A. To get to 20 A I have to seriously increase both the filter duration and the threshold, which feels a bit unsafe...
Measured Iq and Id plots have very noticable first-order oscillations, but everything everything seems reasonably normal and torque response (and the speed control as well) is good:
The magnitude of Iq and Id's oscillations can be somewhat reduced by a more agressive PID tune (essentially increasing the cut-off frequency of the current loop) but this eventually causes to loop to become unstable (as expected).
I have two questions:
- Is the OCP triggering at this level something expected (short current peaks of this type are normal?) or is it indicative of a fault somewhere?
- Is this type of Iq/Id oscillations normal as well?
