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BOOSTXL-3PHGANINV: BOOSTXL-3PHGANINV switching frequency

Intellectual 325 points

Replies: 11

Views: 285

Part Number: BOOSTXL-3PHGANINV

Hello community

I am working with BOOSTXL-3PHGANINV and its provided SW with 28069M launchpad and Teknic_M2310PLN04K motor. The default switching frequency is 40 kHz but when it set to >50 kHz it doesn't work. according to the datasheet it is tested up to 100 kHz. Am I missing sth to customize in the SW?

Thanks and kind regards

  • Hi Makan,

    There should be no difference running at 40KHz and 50KHz. Were you able to adapt it for other frequencies, such as 20KHz? If so, it means you’re doing the right thing to customize the SW.

    One likely cause is the over current protection circuit. You may disable it according to below instructions:

    Regards, Guang

  • In reply to Guang Zhou:

    Hi Guang Zhou

    I change the line 

    #define USER_PWM_FREQ_kHz 

    for 40 khz and 50 khz I have tested and it worked. but for 60 kHz it didn't. I will disable the SCP to see if sth happens.

    Thanks and kind regards

  • In reply to makan sheer:

    Hello Guang

    I removed the OCP. again for switching frequencies > 50 kHz it doesn't run. for lower frequencies down to 20 kHz I tested and it works well. 

    What is the reason OCP should affect dependency on switching frequency?

    Kind regards 

  • In reply to makan sheer:

    Hi Makan,

    OCP shouldn’t kick in especially when motor is not loaded. It is the easiest to check.

    There could be a hard limit on switching frequency in the SW that is enabled. I would look through the SW to see if there is such a limit.

    Regards, Guang

  • In reply to Guang Zhou:

    Hi Guang

    Thank you very much for your time. I will be waiting for your feedback.

    Kind regards

  • In reply to makan sheer:

    Hi Makan,

    I looked through the code as much as I can without a hardware setup, and I think it should work for higher speed as is.

    However it just occured to me that in order to run at high speed you’ll need a high speed motor. The Teknic motor is not suitable over certain speed. Here is an example high speed motor for your reference, which we've used for testing before:

    Part #: B75C123CCBBE
    Vendor: MaxonMotor, Switzerland: http://www.maxonmotor.com

    Regards, Guang

  • In reply to Guang Zhou:

    Hi Guang 

    Thank you for your time. The issue I am dealing with is switching frequency and not the frequency itself just as a reminder.

    So for low-speed motors, we should be able to increase the switching frequency, shouldn't we?

    Kind regards

  • In reply to makan sheer:

    Hi Makan,

    That is not exactly accurate, as a matter of fact, there is a note in the code:

    Regards, Guang

  • In reply to Guang Zhou:

    Hi Guang

    Do you mean, in order to run in higher switching frequencies, the motor should be high speed (low inductance)?

    For example, for a motor with rated 6000 rpm, 300 Hz we can't run with 100 kHz switching?

    If you think so, what is the reason?

    Thanks and kind regards

  • In reply to makan sheer:

    Hi Makan,

    The physical characteristics of the motor, R and L may pose some limitations on the algorithm. Can you do a spot check the phase voltages? This may help to identify if it is a software issue or a motor limitation. 

    Regards, Guang

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