• State
  • Locked Locked
  • Replies 10 replies
  • Subscribers 31 subscribers
  • Views 3629 views
  • Users 0 members are here
Support feedback
Options
Options
Related

This thread has been locked.

If you have a related question, please click the "Ask a related question" button in the top right corner. The newly created question will be automatically linked to this question.

DRV10983 high speed control

Jakub Zych
Prodigy 30 points
Other Parts Discussed in Thread: DRV10983, DRV10983EVM

Hi,

I'm evaluating project where I need to control sensorless BLDC motor. I've recently acquired DRV10983 EVM and encountered few problems while using it.


First of all I'm using sensorless BLDC motor and manufacturer datasheets says that it has 3 phases, 4 magnet poles and with 8V supply it's maximum speed is 15,000 rpm. It's resistance phase to phase is 1.61 ohms and BEMF constant 30mV/Hz.

While using DRV10983EVM GUI I achieved best performance (highest start up success rate) with phase resistance = 1ohm and Kt = 6.42mv/Hz, instead of calculated phase resistance = 0.8ohm (delta design) and Kt = 8mV/Hz.


I achieved almost 100% success rate of start ups and I'm able to control speed up to 10,000 rpm and this is the point where I hit the wall. I can't speed up more. GUI shows that motor is spining with 655 Hz so it's far from driver limit. Also sometimes overcurrent fault appears even when supply shows 0.5A of current consumption and current limit set to 1.2A. Do you have any advices how to solve this problem?

Best regards,

Jakub Zych

  • 0
    TI__Guru** 114905 points
    Hi Jakub,

    Our experts have been notified and should reply soon.
  • 0
    TI__Intellectual 1555 points

    Hi Jakbub,

    Can you share with us screen shot of display tab before you ran into the problem and after?

    Are you referring to lock detection current threshold or over current protection? Over current protection triggers when winding current gets bigger than 3.5A.

    Th lock detection current treshhold is programmable through GUI under advance setting -lock detect section.

    I would recommend you to raise lock detection threshold and see whether it solves the issue.

    thank,

    Seil

    Thanks,

    Seil

  • 0 in reply to Seil Oh
    Prodigy 30 points

    Hi Seil,

    setting Lock Detection Current Threshold to 3.2A  helps with OverCurrent faults, but it haven't help with breaking 10,000rpm speed barrier.

    Below are screens with parameters I'm using and display at maximum speed.

  • 0 in reply to Jakub Zych
    TI__Intellectual 1555 points
    Hi Jakub,

    Two things I can see from "Display" tab is that yous supply voltage is only 9.25V. CAn you check your supply current rating and make sure they are not coming down to 9.25V.

    Your input command is 100% but device is only applying 76.08%. Can you increase the acceleration current limit? It will limit the PWM input.


    Thanks,
    Seil
  • 0 in reply to Seil Oh
    Prodigy 30 points

    Hi Seil,
    I've increased acceleration current limit and it haven't solve speed problem, but it has made start up problematic.

    My motor is designed to run 15k rpm at 8V and as far as i'm concerned that ok with driver datasheet (1000Hz max speed and 8-28 supply voltage). Does driver has any troubles driving motors with supply voltage below 10V?


    I've also found that driver speed up by itself at low speed commands until certain speed is reached. Is this made on purpose?

  • 0 in reply to Jakub Zych
    TI__Expert 3010 points

    Hi Jakub,

    Uncheck 'Enable Inductive AVS' and 'Enable Mechanical AVS' box on Advanced setting page to resolve problem of acceleration at lower speed command value 

    What happens when you increase acceleration current limit?  Can you share phase current plots during fault condition. Are you seeing any fault LED turn ON?

    Startup can be improved by tuning Startup Setting, try reducing 'First Order Accelerate' and 'Second Order Accelerate'. After that try tuning 'Open to Close loop Threshold'

    Let me know how it goes

    Regards,

    Krushal 

  • 0 in reply to Krushal
    Prodigy 185 points

    Hello sir, even i am facing the same issue, why even drv trying to drive motor beyond it own limits i.e.means drv's maximum ratings of current. It should be able to give only 2 amp continuous current only, without any problem to drive motor if user allow so. I dont understand on full speed command 511 my fan gets stop running, restats and its goes on. it shows overcurrent error.

    My motor specification is :

    L = 8.8mH

    r = 2.2ohm

    kt = 550

    Please tell me what kind of fine tuning i will need to do.

  • 0 in reply to Rocky Selva
    TI__Expert 3010 points

    Hi Vijay,

    Can you please provide phase current waveforms and can try changing following couple of setting

    - 'Acceleration current limit' -  can you change it some number instead of disable on basic setting page. DRV10983 doesn't have current loop, it uses parameters like 'Acceleration Current limit', motor resistance, Motor Kt, commanded duty cycle/speed to calculate the applied voltage, so device cannot limit itself in terms of current, it can only control applied voltage.

    - Check box ' Double the output PWM frequency' on Advanced setting page, sometimes higher frequency can provide better control.

    Regards,

    Krushal  

  • 0 in reply to Krushal
    Prodigy 185 points

    Hello sir,

     I have tried with

    1> Acceleration limit setting to 3A-->i got peak performance of motor gets reduced which is not feasible as per application requirement

    2>Double output PWM frequency check-->same overcurrent problem faced and started restarting as before. 

    Here i have shared with you current waveform at the time of overcurrent error:

  • 0 in reply to Rocky Selva
    TI__Expert 3010 points

    Hi Vijay,

    It looks like driver stop driving during the interval highlighted below, did you command zero speed ?

    What is scaling for current waveform ?

    > Acceleration limit setting to 3A-->i got peak performance of motor gets reduced which is not feasible as per application requirement

    Can you set acceleration limit to 3 A and increase value of programmed phase to phase Kt slowly until you achieve maximum speed. What other performance are you not able to meet when you set current limit to 3 A ?

    Regards,

    Krushal