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DRV8301-69M-KIT: Surge or Boost Current for motor startup

Part Number: DRV8301-69M-KIT
Other Parts Discussed in Thread: MOTORWARE

Hardware :

 Invertor :  DRV8301-69M kit based invertor with proper thermal/ heat sink design

 MCU     : F28069M controller

 Software : Motorware / Torque control

 We have customer requirement to use gearless sine wave motor.  Since there are no gears it requires huge torque/ current at startup. 

 Currently we are limiting the current to 40A max, since as per datasheets (DRV-8301-69M Kit) the max current is 40A.

 When the motor is moved very slightly under load conditions it works properly. But without that movement it fails start on its own.

 As per motor specs the motor needs around 70A surge current at startup (from standstill).

My question is can i supply surge current (more than 40A) for few seconds (say 5secs) during startup. As of now I am programing the timer to 5secs and later removing the surge/ boost current. But limited the current to 40A.

Many Thanks  and Regards


  • 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-FOC and InstaSPIN-MOTION User's Guide 

    1. Enable forced angle
    2. Enable stator Rs recalibration before startup
  • Thanks Yanming,

    I tried using Forced angle, I am following below procedure/ method.

    - while starting the motor, call Fly Start and get the shaft speed.

    - If the Motor speed is less than FS_Min Speed then enable the Forced Angle.

    My questions are,

    While I enable the Forced Angle is it automatically made 'False' or we need the turn the flag 'False'?

    When Forced Angle is  'True' ; Is the torque/ Current applied will be Maximum?

    There is very little theory on Forced Angle in user guide. Could you point to me if any more details on Forced Angle.



  • Force angle is an open loop control for start the motor without using the angle from the FAST estimator.

    Which lab are you using?

  • Project11e is being used for proto model testing. 

    We need some help on Force Angle implementation.  If any sample implementation is available

  • The force angle is not implemented if you are using the Hall sensor related function for startup.

    You can set the gMotorVars.Flag_enableForceAngle to "true" and call the function below if you are not using the hall sensor related function for startup.

            // enable/disable the forced angle

    And change USER_ZEROSPEEDLIMIT and USER_FORCE_ANGLE_FREQ_Hz parameters in user.h for setting the force angle frequency .

  • Many Thanks.

    I am not using hall sensors. I would like to solve the startup issue using sensor less technique. I will try your suggestions. The default setting of USER_FORCE_ANGLE_FREQ_Hz looks high to me, so it fails to take and oscillates back and forth.

    for now I will close this thread.