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TMDS2MTRPFCKIT motor speed control software

Ozan Perincek
Prodigy 110 points

Hi,

I have a question regarding the software provided by TMDS2MTRPFCKIT, specifically the closed speed loop mode for Field Oriented Control of PMSM.

I am using this software to run an off the shelf motor. With a 15V input to the motors, I achieve the required speed from the motor (i.e SpeedRef=0.4 and EstimatedSpeed=0.4). At 10V, the motor does not reach the required speed (i.e. SpeedRef=0.4 and EstimatedSpeed=0.3). I am trying to figure out if I have reached a physical limitation or there is something I am not setting in the algorithm variables. It appears there is still some room in the PWM duty cycle dynamic range to further increase speed (i.e the pwm high period is approximately 80% of the maximum allowable PWM period).

If I run the motors on a conroller board provided by the manufacturer, it reaches the specified speed at 10V, however it is using a trapezoidal control system where the PWM frequency is the speed of the motor . With the TMDS2MTRPFCKIT software it reaches half that speed at 10V.

Do you have any suggestions?

Cheers,

Oz

  • 0
    Genius 5170 points

    I am not familiar with the latest TI code so my comments are based on my general understanding of these drives - the most likely reason you are not achieving same RPM at 10V as you did at 15V is lower current. The sine PWM implementation is not able to provide enough current at 10V required to generate the torque needed to obtain your RPM. Note it has nothing to do with TI code , most likely any sine implementation will give you similar result. On the other hand, with trapezoidal implementation the current peak is higher and the drive gets enough current at 10V to achieve the required RPM.  One quick test would be to check the currents in both implementations at 10V.

  • 0 in reply to Arefeen
    Prodigy 110 points

    Thank you.

    Current measurements confirm your answer.