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MCRSP_ACIM_V1.2.0: changing M1_PWM_FREQ ?

Question asked by Vickus Boshoff on May 31, 2018
Latest reply on Jun 7, 2018 by Pavel Sustek

Hi I'm developing a drive for large #ACIM & #PMSM.

We've successfully developed a tiny PMSM drive using #KV31 and KMS.

For this project were in the process for laying out a custom #KV58 CPU with all the bells and whistles.


In order to accelerate the development I've set up a mini version of the system using the aforementioned tiny KV31 drive using #MCRSP_ACIM_V1.2.0 since KV58 is not KMS enabled.

After modifying for my custom hardware everything runs perfectly until I try to change M1_PWM_FREQ. See below captured with M1_PWM_FREQ = 10kHz (default).



I first tried to reduce the frequency too 1kHz (the final application will require this) all control and identified parameters unchanged. 

* Clock & PWM definition
#define M1_PWM_FREQ (1000) /* PWM frequency - 10kHz */
#define M1_FOC_FREQ_VS_PWM_FREQ (1) /* FOC calculation is called every n-th PWM reload */
#define M1_SLOW_LOOP_FREQ (1000) /* Slow loop frequency */


The ID current seems too become inverted. It measures negative while the setpoint is positive and this quickly results in an overcurrent trip. See screen capture below.



Next I tried too re-measure the parameters. This calculates a negative resistance and fails to spin the motor due to overcurrent trip.


M1_PWM_FREQ  -> 7.5kHz actually runs the motor, however Current FOC fails to spin the motor.

Identification at 7.5kHz runs through, but returns very different measurements (Rs(10kHz) = 0.93Ω vs Rs(7.5kHz) = 0.8Ω vs Rs(5kHz) = negative!).#


I thought the issue might be the PDB, however manually confirming initialisation values seem fine.


Can someone perhaps point me in a direction? 

Any help will be greatly appreciated.