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DRV10975: Open loop lock current issue

Part Number: DRV10975

Hi Team,

My customer application is ventilation fan, recently he applies UL certification and need to provide value of open loop lock current. But he found the peak current is not fixed for each lock condition happen. He has no idea how to define the lock current. Could team help explain what is the reason? Is any test method can duplicate same lock current every time.

In the below waveform, CH4 is total current of motor. Customer lock the rotor first then power on the driver, there are 3 lock cycles and the first peak lock current is about 500mA, and about 250mA for 2nd, 3rd peak lock current. Customer did lots of test, the max. peak lock current can up to 700mA.

Thanks a lot.

Vincent Chen

  • Hi Vincent,

    Can you post a screenshot of your GUI settings? Also can you upload a higher resolution picture, I can barely read the picture? (1) Have you tried different OpenLCurr[1:0] settings?

    (2)Just to clarify, you are trying to understand why the current is different between the different motor startups?(3) or you want know what the current will be when going from open loop to closed loop? 

    (4) Can you describe the test you were running for the waveform above? How were you determining when to shut down the motor? was the motor load different? 

    Regards,

    Michael W.

  • Hi Michael,

    Below are screenshot of GUI setting.

    (1) Yes, customer already tried this setting, but if the current limit setting sets lower it will also limit full speed operation.

    (2)(3)(4) Customer lock the motor by hand before starting up the motor and during open loop period as well, when entering close loop's threshold driver detect lock situation and shutdown the motor. Before shutting down, the driver's current increases but the peak current are different every time before shut down.

    Customer wants to know why peak current of shutdown are different? They cannot provide a fixed peak current for UL certification company and cannot explain why?

    Thanks a lot.

    Vincent Chen

  • Hi Vincent,

    The only reason that I can think that the current would get to different levels is because the device would be hitting different fault. Can you check the fault the device is hitting for the different currents and see if the same faults correspond to the same current hit?

    Regards,

    Michael W.

  • Hi Vincent,

    I have seen no update on this thread, did your issue get resolved? I will mark this thread as closed for now but please post again if you need further assistance.

    Regards,

    Michael

  • Hi Michael,

    Thanks a lot for your support and comment.

    Customer had discussed with UL verification services company then to find a way to pass this item. There is no further question.

    Best regards,

    Vincent Chen