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DRV10987: Motor gets shut down while running

Jilna Jayan
Prodigy 100 points
Part Number: DRV10987

Hi Sir,

We are using DRV10987 driver IC for driving  a 24V BLDC motor.

I have tuned the driver for 1600 rpm. These are the motor parameters which we have set and the tuned values.

I was getting maximum rpm when I am entering speed command value as 300.

Now with another motor, at 270 speed command value itself motor is getting shutdown and it is showing current limit error. 

Could you help me to resolve this issue.

Regards,

Jilna Jayan

  • 0
    TI__Mastermind 21805 points

    Hello Jilna,

    Thanks for your question.

    Can you share the motor parameters (operation voltage, maximum speed, maximum current, resistance, Kt, pole count), and your DRV10987 settings (for example a screenshot of our DRV10987 GUI)?

    I would like to also check if you were following our DRV10987 Tuning Guide, and if you are using our DRV10987EVM or your own board?

    Thanks,

    Matt

  • 0 in reply to Matt Hein
    Prodigy 100 points

    Hello Sir,

    We are using our own board and we have followed the DRV10987 Tuning Guide.

    The Motor parameters & screen shot of DRV10987 GUI are given below:

    Operating Voltage - 24VDC

    Maximum Speed - 1700rpm

    Maximum Current - 1.5A

    Phase to phase resistance - 1.3ohm

    Kt - 117

    Pole Count - Stator:12 pole & Rotor - 8 pole

    We are not able to increase the motor speed above 52% duty cycle. If we incraese above motor is getting shut down.

    Please help us to resolve this issue and let us know how to achieve 1700 RPM.

    Regards,

    Jilna Jayan

  • 0 in reply to Jilna Jayan
    TI__Mastermind 24415 points

    Hi Jilna,

    Thanks for sharing the motor parameters. The GUI screenshot image is broken. Can you re-upload the image? How much is the phase current (peak) that you are seeing at 52% duty cycle? If the peak is 3A or above, then we will have to tune the lead time. Can you try changing the lead time till the estimated Kt matches the programmed Kt ? Refer to this app note on tuning lead time.

    Regards,

    Vishnu.

  • 0 in reply to Vishnu Balaraj
    Prodigy 100 points

    Dear Sir,

    Attached the GUI screenshot image.

    Thanks for the information.

    Let me tune the lead time and check the issue is resolved or not.

    Regards,

    Jilna Jayan

  • 0 in reply to Jilna Jayan
    TI__Mastermind 21805 points

    Hi Jilna,

    You need to click the Insert/Edit Media button to insert the image in the post. I couldn't see the image in your last post.

    Thanks,

    Matt

  • 0 in reply to Matt Hein
    Prodigy 100 points

    Dear Sir,

    Attached the GUI screenshot.

  • 0 in reply to Jilna Jayan
    TI__Mastermind 24415 points

    Hi Jilna,

    Thanks for sharing the GUI screenshot. Since your motor is rated for 1.5A (rms), I recommend reducing the IPD current threshold to 2A (peak). Since Rm (ph-CT) is 0.65 ohms, can you program Rm to 620.8m (closest available value to 650m)? Can you measure Kt to make sure 117 mV/Hz is accurate? Here is a video on how to measure Kt using oscilloscope. Can you try changing the lead time till the estimated Kt matches the programmed Kt ?

    Regards,

    Vishnu

  • 0 in reply to Vishnu Balaraj
    Prodigy 100 points

    Hi Sir,

    As suggested, I reduced the IPD current to 2A and Rm is set to 620.8m.

    Also I once again measured the Kt, which was coming in between 100 - 110mV/Hz. Now the lead time is set to 220u.

    With these modifications, above 50% duty cycle motor is shutting down and lock code is displaying current Limit error. 

    Please let me know what further do I need to adjust to achieve the required RPM without shutting down the motor.

    Regards,

    Jilna Jayan

  • 0 in reply to Jilna Jayan
    TI__Mastermind 24415 points

    Hi Jilna,

    Tuning low resistance motors could be challenging. With software current limit disabled, low phase resistance motors draw very high current and trigger current limit. To avoid this, it is recommended to enable software current limit and set to maximum peak phase current at maximum speed with full load. 

    Sometimes, because of the implementation of the software current limit, the motor might not be able to accelerate to the target speed. In such cases, the Speed Command Buffer will be lower than the Speed Command. This is because the programmed Kt value is wrong and set too low. The solution is increasing the Kt value and checking whether the motor can reach maximum speed. If the difference between Speed Command and Speed command Buffer gets closer, continue increasing the Kt until both are same.

    Regards,

    Vishnu.

  • 0 in reply to Vishnu Balaraj
    Prodigy 100 points

    Hi Sir,

    Based on your suggestion, I have enabled the software current limit and then adjusted the Kt value to make the Speed command buffer same as the speed command.

    Now the motors are running fine without shutting down. Also we were able to achieve the required RPM.

    Thank you so much for the support.

    Regards,

    Jilna Jayan