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DRV11873EVM - Motor stops over 9500rpm

Kawai
Guru 19775 points
Other Parts Discussed in Thread: DRV11873EVM, DRV11873

Hi Team,

Our customer is evaluating the device using the DRV11873EVM.

They want to use the device to control the motor at 10000rpm, but the motor always stops at around 9500rpm.

What is the problem ? Is there anything that limits motor speed ? LS pin setting ?

[Customer Condition]
- Motor type : Star wiring motor
- have no changes on the EVM
- They tried changing VCC or PWM frequency, but no change.
- Load current at 9500rpm is 100mA, 150mA(peak), not in current limit.

Best Regards,
Kawai

  • 0
    TI__Mastermind 26065 points

    Hi Kawai

    Could you give the pole pair (PP) numbers of your motor? Based on RPM = 60*FG/PP. We need to know the MAX FG when it at 9500rpm.

    DRV11873 has a fixed MAX speed limit of the internal control logic. The limit is FG < 475Hz@FS=0 and 950Hz@FS=1 .

    Besides calculate the FG, you can directly measure the FG signal from the FG pin (with pull up to VCC or V5). If it is true reached the limit. We can do litte about it other than lower down the speed.

    Thanks,

    Wilson Zuo

    Motor Application Team

  • 0 in reply to Wilson Zuo
    Guru 19775 points

    Hi Wilson-san,

    Thank you very much for your reply.

    The Pole Pair (PP) is "6", calculating FG = RPM * PP / 60 = 1000Hz@10000RPM.

    I understood that this is over the limit of device control logic.

    To achieve 10000RPM, maybe you may need to choose motor witch has lower pole pair numbers.

    Best Regards,
    Kawai

     

  • 0 in reply to Kawai
    TI__Mastermind 26065 points

    Hi Kawai

    Yes. Motor with lower pole pair numbers usually comes with lower FG and higher RPM.

    Thanks.

    Wilson Zuo