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Original question:

TMS320F28069M: Regarding Fastest Motor Startup with Full Load with Motor Alignment Considerations

TMS320F28069M: Suppress inrush current at startup

Sh.Sasaki
Guru 13625 points

Part Number: TMS320F28069M

Hi experts,

My customer is using the lab10 project for the original board.
RS calibration cannot be used because the customer's application requires a fast system startup. This may cause a sudden increase in speed due to the position of the rotor at startup. When the speed rises rapidly, the current also rises rapidly to USER_MOTOR_MAX_CURRENT.Is it possible to set this current rise lower than USER_MOTOR_MAX_CURRENT?
The customer wants to suppress the inrush current at startup.

Best regards,
Sasaki

  • 0
    TI__Guru** 116850 points

    You might adjust the Kp and Ki of the speed PI regulator to control the torque current increasing rate. 

    Or set a specific maximum current for startup by calling the below functions.

    TRAJ_setMaxValue(ctrlHandle->trajHandle_spdMax, maximumCurrent);
    TRAJ_setMinValue(ctrlHandle->trajHandle_spdMax, -maximumCurrent);

  • 0 in reply to Yanming Luo
    Guru 13625 points

    Hi Luo-san,

    Thank you for the information.

    Yanming Luo said:
    You might adjust the Kp and Ki of the speed PI regulator to control the torque current increasing rate. 

    The customer is using lab10b, which is InstaSPIN-MOTION.
    Therefore, the speed Kp and Ki cannot be adjusted.

    Yanming Luo said:

    Or set a specific maximum current for startup by calling the below functions.

    TRAJ_setMaxValue(ctrlHandle->trajHandle_spdMax, maximumCurrent);
    TRAJ_setMinValue(ctrlHandle->trajHandle_spdMax, -maximumCurrent);

    The value is 0 because these functions default to:

      // set the default maximum speed trajectory module parameters
      TRAJ_setIntValue(obj->trajHandle_spdMax,_IQ(0.0));
      TRAJ_setTargetValue(obj->trajHandle_spdMax,_IQ(0.0));
      TRAJ_setMinValue(obj->trajHandle_spdMax,_IQ(0.0)); // not used
      TRAJ_setMaxValue(obj->trajHandle_spdMax,_IQ(0.0)); // not used 
      TRAJ_setMaxDelta(obj->trajHandle_spdMax,_IQ(0.0)); // not used

    Therefore, a mximum current cannot be reduced any more.

    Is there any other way?

    Best regards,
    Sasaki

  • +1 in reply to Sh.Sasaki
    TI__Guru** 116850 points

    You might tune the control bandwidth and acceleration if you are using instaspin-motion. And also, having an incorrect Rs value (especially a value higher than the actual Rs) will make the start-up behave poorly. You might refer to chapter 14 "Managing Full Load at Startup, Low-Speed and Speed Reversal" in InstaSPIN-FOCTm and InstaSPIN-MOTIONTm User's Guide,  http://www.ti.com/lit/ug/spruhj1h/spruhj1h.pdf 

    1. Enable forced angle
    2. Enable stator Rs recalibration before startup
  • 0 in reply to Yanming Luo
    Guru 13625 points

    Hi Luo-san,

    Thank you for the information.

    RS calibration cannot be used because the customer's application requires a fast system startup.

    The customer also made adjustments by referring to Chapter 14 "Managing Full Load at Startup, Low-Speed and Speed Reversal" in the MOTION User Guide, but the problem was not resolved.

    After all, is there any way they can solve the boot problem other than doing Rs recalibration?
    If Rs recalibration is mandatory, we tell our customers that they have to do this.

    Best regards,
    Sasaki

  • +1 in reply to Sh.Sasaki
    TI__Guru** 116850 points

    Enable force angle and Rs recalibration are key factors to improve the startup performance if the user want to start the motor at different conditions with full load, especially, the temperature of the motor stator windings changes significantly.

  • 0 in reply to Yanming Luo
    Guru 13625 points

    Luo-san,

    Thank you for the information.

    I got it.

    Best regards,
    Sasaki