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DRV10983EVM: No Load Current Issues and Motor Heating

Part Number: DRV10983EVM

We are using Maxon sensorless BLDC motor (Part No. B7B93E3A6E07 - datasheet attachedECXSQ16L.pdf) along with the drive from Texas Instruments (Part No. DRV 10983). It is a low inductance motor of 0.12mH. The no load current in datasheet is mentioned as 139mA. But in our tests its taking 280mA and the motor is getting heated up. What could be the possible reason for this?

  • Hi Felcy,

    Thanks for posting your question in MD forum and thanks for sharing all the details. There could be several reasons for the device to not output the rated no load current. If you can share the device EEPROM config file, I can take a look and see what parameters need to be tweaked to optimize the performance. You can save the device EEPROM settings by clicking the save button in the GUI as shown below and share it to me. 

    Regards,

    Vishnu.

  • working_closedloop_aug_26th.csvDear Vishnu,

    Please find attached the EEPROM config file.

    Thanks and Regards,

    Felcy Varghese

  • Hi Felcy,

    Are you able to spin the motor in closed loop? Is the motor drawing 280 mA in open loop or closed loop? I checked your EEPROM settings. Below are few recommendations:

    1.Program Kt to 52.2 mV/Hz

    2. Reduce open loop current to 0.8A

    3. If you consider Align and go as a startup option, please disable IPD. Align and go is more reliable and requires no tuning compared to IPD.

    4. If you are able to spin in closed loop, keep tweaking lead time till the estimated Kt gets close to 52.2 mV/Hz. Estimated Kt can be read using the GUI in display tab.

    Regards,

    Vishnu.

  • Dear Vishnu,

    Yes we are able to spin the motor in closed loop. Motor is taking 280 mA in closed loop.

    We did the changes as per your recommendation and got the lead time as 200 micro seconds to get the estimated value close to 52.2mV/Hz. Still the motor is getting heated with the same current.

    We talked to motor manufacturer also regarding this problem. They said that as the motor is low inductance one they prefer using additional inductance in the circuitry. What are your comments on this? Kindly suggest accordingly.

    Thanks and Regards,

    Felcy Varghese

  • Dear Vishnu,

    Just following up if you had the time to go through the previous thread. Kindly let me know if any additional information is required.

    Thanks and Regards,

    Felcy Varghese

  • Hi Felcy,

    Thanks for the follow-up. Is 280 mA peak-peak , peak or RMS current? What is the rated voltage of the motor? Are you within the voltage limit? If the applied voltage to the motor is above rated value, motor can draw more current. Can you further tweak lead time to see if you can bring down the phase current? You might see estimated Kt dropping below 52.2 mV/Hz bu that should be fine.

    Regards,

    Vishnu.

  • Dear Vishnu,

    We measured 280 mA in the power supply. We put a inductance in series with each motor phase and the current value has now come down to 170 mA. We are still under testing to check whether there is any degradation in the performance.

    Thanks and Regards,

    Felcy Varghese

     

  • Hi Felcy,

    Is 280 mA the current drawn from the power supply. Didn't you say this is the motor phase current? I don't see the purpose of adding an inductor to reduce the motor phase current. Adding resistor to the phases will make more sense to reduce the motor phase currents. Can you respond to the questions in my previous post?

    Regards,

    Vishnu.

  • Dear Vishnu,

    280 mA is the reading taken from the power supply hence will be the average value the motor is taking. The motor is rated at 18 V but as per the discussion from the motor manufacturer the motor can work upto 28 V. In the current set up we are giving 24 V as supply and limiting the duty ratio to 75% so basically working at 18 V only.

    Also the inductor value was selected as per the application note in the below link

    Kindly suggest accordingly.

    Thanks and Regards,

    Felcy Varghese

  • Hi Felcy,

    I don't recommend reading the current drawn from the power supply and comparing this with the rated motor current in the datasheet. Device has internal loads that will consume some amount of power so I would recommend using a current probe to measure the current drawn by the motor and compare this value with the rated motor current in the datasheet. 

    Regards,

    Vishnu

  • Hi Felcy,

    I will close this for now, since I haven't heard a response back. If you want a follow-up, please feel free to reply to this thread or create a new thread.

    Regards,

    Vishnu