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DRV11873 DataSheet Qustions

cafain
Mastermind 6365 points
Other Parts Discussed in Thread: DRV11873

Hi

DRV11873 4 Questions.

1) It's written on Figure1 and 3 of page7 of data seat (SLWS237A) with "100% Duty".     

    Can PWM input be input to Duty 100% ?

2) It's revolving to 20000rpm by Duty 100% in Figure7 of page8 of data seat.     

    How many volts is  VCC ? (2.7V? or 3.3V? or others)

3) Page8 of Figure8 is revolving to 25000rpm by VCC=16V.     

    How many percent is  Duty? (50%? or 100% or others)

4) It's revolving even at most 25000rpm by a chart of Figure8.   

    Please tell the condition to make them revolve to 25000rpm.   

   (The specifications of the motor and loads, etc.)

Best regards

  • 0
    TI__Expert 8885 points

    cafain,

     1. Can PWM input be input to Duty 100% ? Yes, as per my understanding duty cycle is 100% for this test.

    2. It's revolving to 20000rpm by Duty 100% in Figure7 of page8 of data seat.     How many volts is  VCC ? (2.7V? or 3.3V? or others)-  at nominal 12Volt

    3. Page8 of Figure8 is revolving to 25000rpm by VCC=16V.    How many percent is  Duty? (50%? or 100% or others) - It must be 100% duty.

    4.  It's revolving even at most 25000rpm by a chart of Figure8. Please tell the condition to make them revolve to 25000rpm.

       (The specifications of the motor and loads, etc.)

    All the data-sheet characterization are taken with two motors and back-emf constant of motors is major differentiation. The high speed motor has back-emf constant value such that it reaches 25000rpm at 16Volt, and low speed motor has back-emf constant such that it reaches 1600rpm at 16Volt. Both are driven at constant duty cycle of close to 100%.

    I hope this clarifies your doubt.

    Best Regards

    Milan-Motor Application Team

     

  • 0 in reply to Milan Rajne
    Mastermind 6365 points

    Hi Tram

    I would like to thank detailed answers.
    I understand the contents.

    Best regards

  • 0 in reply to Milan Rajne
    Mastermind 8375 points
    Hi Milan

    I am the same team as cafain.
    When showing the specification of our customers motor, can you answer how many revolution we can turn a motor by this driver?

    Regards,
    PAN-M
  • 0 in reply to PAN-M
    TI__Expert 8885 points

    Hi PAN

    Actual mechanical revolution depends upon number of poles. In electric Hz, DRV11873 can deliver ~950Hz at FS=1 and ~470Hz at FS=0. 

    Best Regards

    Milan

  • 0 in reply to Milan Rajne
    Mastermind 8375 points
    Thank you for support.
    PAN-M
  • 0 in reply to PAN-M
    Mastermind 8375 points
    One more question.
    In case of 25,000 revolution, is a two pole motor needed?
    Regards,
    PAN-M
  • 0 in reply to PAN-M
    TI__Expert 8885 points

    PAN,

    The eq is : mechanical rpm = 120* f/P , f is electric Hz and P - number of poles

    That means with 400 Hz two pole can reach = 120 *400/2=24000 rpm

    So based on DRV11873 freqeuncy range you can figure out number of motor poles.

     

    Best Regards

    Milan-Motor Applicaiton Team

  • 0 in reply to Milan Rajne
    Mastermind 8375 points

    Milan

    Our customer have added questions.
    Is "electric Hz"  "FG output"?
      When the FS=1 mode, would FG output be able to correspond to max. 950Hz?
    As for mechanical rpm = 120* f/P, where can 120 be calculated?
      It's written on page 10 of a data seat with "RPM = (FG*60)/pole pairs".
      Are these meaning different?
    When a pole is two and a frequency is more than 400Hz, would it be able to revolve beyond 24000 rpm?
     Or, a spin is restricted by 24000 rpm, and can't any more revolution be done?

    Regards,
    PAN-M

  • 0 in reply to PAN-M
    TI__Expert 8885 points

    PAN

    Yes FG is electric Hz.

    Both RPM eqs are same, P is number of poles and Pole-pair=P/2.

    For two pole motor, freqeuncy higher than 400Hz will increase the mechaical rpm too based on above equations.  There could be two limiting factors:

    1. Motor  mechanical desgin should done properly to operate at higher rpms, without causing any shaft vibration.

    2. Motor back-emf constant should be such value that at 12V, it allows motor to reach beyond 400Hz.

    Best Regards

    Milan-Motor Application Team