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DRV10983EVM: Motor running but not at full speed with DRV10983EVM

Part Number: DRV10983EVM
Other Parts Discussed in Thread: DRV10983, DRV10974

Hello,

We are running a 1.8" HDD motor (low voltage, low back EMF BLDC motor) with the DRV10983EVM but are experiencing the following issues:

  • motor does not start at low speed inputs (does not run when input is approx. < 300)
  • motor does not run at expected max speed (when speed input = 511, max speed measured by tachometer = 3500 RPM, max speed expected > 10,000 RPM)
  • motor current draw is higher than expected (measured = 0.2 A, expected = 0.1 A)
  • configuring motor to run is very sensitive to the control coefficient (only runs when control coeff. = 0.25)

We have followed most of the tuning guide provided for the DRV10983 but are still experiencing these issues. Below are screenshots of the DRV109XX GUI settings that run the motor best so far:

  • Hello Abhay,

    What is the inductance, resistance, and back-EMF constant of the HDD motor you are using? Take a look at [FAQ] DRV10x Selection Guide to see if it is in the range of acceptable use for DRV10983.

    I cannot guarantee DRV10983 will be able to properly spin the HDD motor, since it was not designed with the HDD application in mind.

    Your screenshots were not attached to the post, please use the "Insert File" button (paper clip image).

    Thanks,

    Matt

  • Hi Matt,

    Thank you for the quick response. I've reattached the GUI settings screenshots as files - please let me know if they do not show. Our motor specifications are as follows:

    • Inductance: 448.1 uH
    • Resistance: 4.5 Ohms (phase to phase, wye-connected)
    • Back-EMF Constant: 2.3 mV/Hz

    Thank you for your help!

    Best,

    Abhay

  • Hi Matt,

    Thank you for the quick response. I've reattached the GUI settings screenshots as files - please let me know if they do not show. Our motor specifications are as follows:

    • Inductance: 448.1 uH
    • Resistance: 4.5 Ohms (phase to phase, wye-connected)
    • Back-EMF Constant: 2.3 mV/Hz

    Thank you for your help!

    Best,

    Abhay

  • Hi Abhay,

    Thanks for sharing the details. Can you please answer below questions to help us understand the issue better?

    1. How many pole pairs does this motor have?

    2. Why is BEMF constant programmed to 7.33 mV/Hz while the actual value is 2.3 mV/Hz?

    3. Do you see any fault getting triggered at low speeds?

    4. Since you mentioned phase current as 0.1A, I'm guessing this to be a low power motor. What is the supply voltage Vcc? If Vcc is below 12V, then I would recommend using DRV10974. DRV10983 is designed for high power applications (up to 3.2A and 28V). 

    Regards,

    Vishnu 

  • Hi Abhay,

    Just wanted to follow-up with you to see if you have any updates.

    Regards,

    Vishnu