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MCT8329A: Fastly start and accelerat fault

Part Number: MCT8329A
Other Parts Discussed in Thread: MCT8316A

Dear sir,

   When the PWM control signal from 0% to 100% is applied to the motor within 300ms, sometimes the speed of the motor does not increase correspondingly, but runs at a lower constant speed, and is not controlled by the speed regulation. What should be done so that the motor can be started and accelerated quickly. Thanks a lot!

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      {
        "idx": 0,
        "id": "isd_config",
        "value": "0x7E804C4E"
      },
      {
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        "id": "motor_startup1",
        "value": "0x6B1E65BB"
      },
      {
        "idx": 2,
        "id": "motor_startup2",
        "value": "0x052D2799"
      },
      {
        "idx": 3,
        "id": "closed_loop1",
        "value": "0x3025E600"
      },
      {
        "idx": 4,
        "id": "closed_loop2",
        "value": "0x02A1A4A9"
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      {
        "idx": 5,
        "id": "closed_loop3",
        "value": "0x3144A001"
      },
      {
        "idx": 6,
        "id": "closed_loop4",
        "value": "0x001AC953"
      },
      {
        "idx": 7,
        "id": "const_speed",
        "value": "0x30010000"
      },
      {
        "idx": 8,
        "id": "const_pwr",
        "value": "0x0C800640"
      },
      {
        "idx": 9,
        "id": "150_deg_two_ph_profile",
        "value": "0x24DB7200"
      },
      {
        "idx": 10,
        "id": "150_deg_three_ph_profile",
        "value": "0x48DB6946"
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      {
        "idx": 11,
        "id": "ref_profiles1",
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      {
        "idx": 3,
        "id": "ana_trim6",
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      {
        "idx": 4,
        "id": "ana_trim7",
        "value": "0x009D97DE"
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        "idx": 5,
        "id": "ana_trim8",
        "value": "0x00005242"
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      {
        "idx": 6,
        "id": "ana_trim9",
        "value": "0x008DC71A"
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      {
        "idx": 7,
        "id": "ana_trim10",
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        "id": "fault_config1",
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        "idx": 0,
        "id": "gate_driver_fault_status",
        "value": "0x00000000"
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      {
        "idx": 1,
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    ],
    [
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    ],
    [
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      {
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      {
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    ],
    [
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      {
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}

  • Hi Joe.

    Thank you for providing you register configuration! I will review the register settings and get back to you by Dec. 20th.

    Regards,

    Joshua

  • Hi Joshua,

            The operating voltage is 7.5V, and the motor KV value is 6000. 

             Thanks!

  • Hi Joshua,

          MOSFET‘s RDS= 4mR,Continuous Drain Current(Rating)is 50A,Pulsed Drain Current(Rating)is 200A.When we set the "SEL_VDS_LVL" to 0.8V, MCT8329A  still often produced OCP_VDS_FAULT error.

         Thanks!

  • Hi Joe,

    Would you mind also providing:

    1. the peak current rating of the motor?
    2. the value of the current sense resistor that is being used?

    These two values will affect the register changes we recommend making.

    Regards,

    Joshua

  • Hi Joshua,  

    1. the peak current rating of the motor-----it is 60A(Max),and no-load current is 2.5A when voltage is 7.5V
    2.  current sense resistor--------it is 0.001R

    Thanks!

  • Hi Joe,

    The lack of speed regulation is likely due to CLOSED_LOOP_MODE, bits 0-1 in register CONST_SPEED, being set to Disabled. To have speed regulation, CLOSED_LOOP_MODE needs to be set to Speed Loop (1b).

    Since the motors peak max current is 60A and the VREF_SEL settings chosen is UNI-DIRECTIONAL CSA, I would recommend changing the CSA_GAIN setting to 40 V/V. This new CSA_GAIN will being max measurable current by the CSA down to ~65A from the current 525A increasing the total resolution of the CSA. To calculate the max measurable current of the CSA you can use the following equation for Uni-directional mode:
    Max Current = (3-(3/8))/(RSENSE*CSA_GAIN)
    To calculate the max measurable current of the CSA in Bi-directional mode the following equation can be used:
    Max Current = (3-(3/2))/(RSENSE*CSA_GAIN)

    An example of register settings which can be used to achieve fast acceleration can be found in the MCT8316A Tuning Guide. The register values for the MCT8316A cannot be directly copied over to the MCT8329A but it can be a helpful guide.

    Regards,

    Joshua