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TMS320F28069: DRV8301-HC-Kit - limited maximum speed

Part Number: TMS320F28069

Hello,

To control our BLDC motor which has a built-in encoder, we are using  DRV8301-HC-Kit and testing using lab 12b. We are not able to reach the maximum speed we need. The motor is rated at 900 rpm but the motor speed does not exceed 490 rpm with lab 12b. We have ensured that all parameters are correct using lab 2a and b. Also, we have verified the required parameters like inertia and friction using lab 12a. Also, increasing the input voltage DOES NOT help to increase the motor speed. With that being said, I have provided the CCS results including all important variables which should help analyze the operation of the motor. Please see the word file attached. We highly appreciate your URGENT response.  If we need to do overmodulation or field weakening, can you provide the source code that works with encoder ? E2e.docx

  • 1. What's pole pair of the motor? And what USER_IQ_FULL_SCALE_FREQ_Hz is set in user.h?
    2. What's USER_MOTOR_MAX_CURRENT set in user.h? Try to increase this value and see what happen.

    Btw, for overmodulation and field weakening, please refer to lab10 (OVM) and lab09 (FW) that include all source codes.

  • 1- 8 pole pairs. USER_IQ_FULL_SCALE_FREQ_Hz= 20 hz
    2- Was set to 10 Amps which gave use max speed of 400 rpm. we increased it to 20A which gave us 480 rpm max. After that, increasing USER_MOTOR_MAX_CURRENT has no effect on speed.

    Any suggestions why we are not getting the max speed?
  • TI Team, Do you guys have any suggestions??
  • 1. Are you setting USER_IQ_FULL_SCALE_FREQ_Hz= 20 hz? Or is it a typo? You should change it to a higher value, like 400Hz if you are using 20Hz at here.
    2. Please check the electrical frequency of the current when the motor is running with 400rpm, make sure the pole pairs is set to a correct value as the motor spec.
    3. What's the rated speed of the motor? And what's the flux? You may increase the dc bus voltage to see if the maximum running speed will increase also, that helps you know if the motor needs field weakening control for high speed.
    4. You may try to use lab05d to run the motor, that will help you to check if the encoder is configured correctly.
  • 1. USER_IQ_FULL_SCALE_FREQ_Hz is actually 1000
    2- motor has 16 poles. Pole pair set to 8.
    3. Rated speed is 800 rpm. increasing DC bus voltage does not help with speed.
    4. We did. The encoder is configured correctly.

    do you have any other suggestions?
  • Did you run lab12a and identify the inertia correctly?

    You might run the lab5c to identify the inertia of the motor, and then run lab5d or lab5e to see if the motor can run up to the target speed/frequency you want. If yes, that means the encoder is not set correctly. If no, that means the motor needs to use field weakening control for high speed.