Subject: PMSM Motor Drawing Higher Power at Low RPM – Guidance on Parameter Tuning
Hello Expert,
I have developed a custom board based with STM32F303VET6X, using two IPMs and 0.47 Ω shunt resistors, similar to the STEVAL-IHM045V1 design. The board utilizes the internal op-amps and comparators for current sensing and protection.
With MCSDK 6.41, I have successfully run two PMSM motors using this custom board, equivalent to the setup with STEVAL-IHM045V1 power board and STM32F303E-EVAL control board.
However, I am observing that at lower RPM, the motor exhibits audible noise and higher input power consumption compared to a typical ECM motor operating at similar conditions/ airflow/rpm. In the custom board livewatch target RPM is achieved always, but I am unsure which parameters should be optimized in MCSDK to reduce input power and improve efficiency.
As an random experiment, I thought to play with RSH. I changed the shunt resistor values to see the effect on power consumption:
RPM Rsh (Ω) Input Power (W)
| 1540 | 0.47 (on custom board) | 44 |
| 1540 | 0.33 (changed in software) | 34 |
Reducing Rsh in software appears to decrease the measured input power, but I’m not sure if this improvement reflects true efficiency or if it’s due to changes in current sensing calibration.
Could you please advise which MCSDK parameters (e.g., FOC tuning, current sensing calibration, or control loop settings) I should focus on to optimize performance and minimize power at low speeds?
Best regards,
