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DRV11873: Question of PWM resolution and motor contorl

na na78
Guru 16770 points
Part Number: DRV11873

Hi

I have question of DRV11873.

1.
What is the relationship between PWMinput and PWMoutput?
(PWMin duty : PWMout duty =1:1?)

2.
Can we know what resolution of PWMin and PWMout is?

3.
In the customer's system, the motor may spin slowly in reverse when FG is in 10Hz to 20Hz.
What do you think the condition under which motor spins in this way?

BestRegards

  • 0
    Guru 16770 points
    Hi

    I would appreciate it if you could reply.

    And please let me know if you have questions.

    BestRegards
  • 0
    TI__Intellectual 770 points

    1. Yes. it is 1:1.

    2. 1% resolution. It took 1 sec to reach 95% speed command and another 1 sec from 95% to 100% speed command. Total is 2 sec.

    3. Adjust current limit. Would please you share with us phase current / voltage waveforms? 

    Thank you,

    Janet   

  • 0 in reply to Janet Yi
    Guru 16770 points
    Hi Janet

    Thank you for your reply.

    >2. 1% resolution. It took 1 sec to reach 95% speed command and another 1 sec from 95% to 100% speed command. Total is 2 sec.
    Is it possible to explain by bit? (like "xx bits resolution")

    >3. Adjust current limit. Would please you share with us phase current / voltage waveforms?
    I'm asking it to the customer. (All phase waveforms, possibly)

    By the way, Rcs is set as 3.3Kohm.
    Should its value be changed?

    BestRegards
  • 0 in reply to na na78
    Guru 16770 points

    Hi

    I'd like to add waveform info.

    BestRegards

  • 0 in reply to na na78
    TI__Intellectual 770 points
    Would please you share with us the motor resistor information (phase to phase or phase to CT) ?

    Thank you,
    Janet
  • 0 in reply to Janet Yi
    Guru 16770 points
    Thank you for your reply.

    Sorry, what is motor resistor information?

    Do you mean 3-phase waveform?
    What is phase to CT?


    BestRegards
  • 0 in reply to na na78
    TI__Expert 3010 points
    Hello,

    Measure resistance using multi-meter or something between 2 phase cables U-V, U-W or V-W.

    Regards,
    Krushal
  • 0 in reply to Krushal
    Guru 16770 points
    Hi Krushal

    Thank you for your reply.

    >Measure resistance using multi-meter or something between 2 phase cables U-V, U-W or V-W.
    The resistance between two phase is 0.8ohm.

    As the other information of motor (VCC=12V),
    Startup torque : 50mNm
    Startup current : 5.5A
    RotationSpeed (no load) : 11700rpm

    In addition, we found motor start up fails with the higher voltage.

    (VCC OK/NG)
    8V 10/0
    9V 1/9
    10V 8/2
    11V 4/6
    12V 3/7
    13V 2/8
    14V 0/10
    15V 0/10

    What do you think the cause of it?

    BestRegards
  • 0 in reply to na na78
    Guru 16770 points

    Hi Krushal



    Our customer wants to use DRV11873 properly.

    And there is following request.

    >2. 1% resolution. It took 1 sec to reach 95% speed command and another 1 sec from 95% to 100% speed command. Total is 2 sec.
    Is it possible to explain by bit? (like "xx bits resolution")

    Is it 6 bit resolution? I guess.

    I hope it would be clear.
    Could you please tell us your view?



    BestRegards

  • 0 in reply to na na78
    Guru 16770 points
    I will check the drv11873 operation again.
    So I close this thread this time.
    Thank you for your cooperation.

    BestRegards