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DRV8308EVM: motor rotates with noise and gets hot after a while

Hong Sun
Intellectual 300 points
Part Number: DRV8308EVM
Other Parts Discussed in Thread: DRV8308,

I am evaluating DRV8308 chip for my motor using DRV8308EVM.  it is known that hall sensor is 0 degree aligned (from vendor with integrated motor/hall sensor).  I started motor using the open loop: pwm mode and 120 deg commutation.  motor can rotate but with noise and bumpy visible bumpy rotation and motor can get really hot after a few minutes.   Hall sensor's output shows the uneven speed too.   I adjust ADVANCE value and speed will be impacted but the noise, uneven speed and motor getting hot remains.   I tied to change to 180 commutation (sine) and it won't help.   Lockn signal come and go.    Any tips what should I do to improve the smoothness of rotation and reducing the heat generated by motor?

The motor's specification: 12V with no load speed 63400 rpm, nominal speed 46800rpm  (the motor is integrated with a 15:1 gearhead and with a simulated load).  phase resistance = 12ohm, inductance 0.118 mH.  I have run the motor with the motor mfg's controller which can run quietly and won't get hot at all.

thanks,

Hong

  • 0
    TI__Genius 14487 points
    Hello Hong,

    Do you have the Hall sensors and the motor phases connected to the correct terminals? Sometimes if the order of the Hall sensors and motor phases do not correspond, you can have issues like this.

    Also are the Hall sensors single-ended or differential?
  • 0 in reply to James Lockridge19
    Intellectual 300 points
    Hello James,

    The hall sensors are single-ended. For the connection, I did wire one pair of hall sensor wrong. After fixing that problem, motor runs much smoothly and motor get warm but not super hot anymore. However the rotation noise get quieter but it is still louder than the controller from the motor vendor, where both hall sensor and encoder are used to perform the motor commutation. What do you think, will that be the limitation of using hall sensors only for motor commutation?

    thanks,

    Hong
  • 0 in reply to Hong Sun
    TI__Genius 14487 points
    Hong,

    It may be a limitation of the driving method as you suggest, but we might be able to improve it.

    Do you know what kind of driving method the motor vendor's controller uses? Can you share with me a datasheet or some information on this controller?

    How does the noise performance compare between the 120 trapezoidal and 180 sinusoidal commutation methods for the DRV8308?
  • 0 in reply to James Lockridge19
    Intellectual 300 points

    Hello James,

    The vendor's controller is :maxon EPOS4 compact 24/1.5 CAN  (https://www.maxonmotor.com/maxon/view/product/control/Positionierung/546714).  I don't know what kind of driving method it uses.  But it UI requires using encoder (can NOT choose hall sensor only) and I just assume sinusoidal commutation.    BTW the  motor is Maxton EC 6 455419.

    I did compare the 120 and 180 commutation method and I can't tell the difference of its noise performance.  I tried to adjust ADVANCE and no noticeable difference there neither.   If I let the system auto-adaptive and it gets worse.  I tried to have the PWMF to 100Khz and no noticeable different neither so I set it at 50Khz for the tests.   Simply using oscilloscope to monitor Hall sensor U+, the waveform looks stable but I don't have instrument to see how its speed/frequency looks like.   BTW, is there a test point of current (R22-- current sense resistor, hard to get a good contact by probing the leg of the resistor). 

    thanks,

    Hong

  • 0 in reply to James Lockridge19
    Intellectual 300 points

    Hello James,

    My college think the noise performance between DRV8308 and vendor's controller is similar.  Since I have no instrument to measure it, I will take the noise performance is not an issue with DRV8308 then.   Please let me know if you find out anything interesting. 

    thanks,

    Hong