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Original question:

DRV8308EVM: closed loop at slow speed, running problem

DRV8302: Motor Stuttering issue at slow speeds

Needhu Gunasegaran
Intellectual 2890 points
Part Number: DRV8302
Other Parts Discussed in Thread: DRV8301, , MOTORWARE

Hi,

My customer wants to implement a Sensorless BLDC motor controller.

Conditions and parameters:

Min speed of 300 RPM

Start time 150ms

4Pole Motor with downstream gear box (32:1)

DRV8301/DRV8302 EVM is used with ISO-Control Card

TI Motorware SW

Issue:

Motor doesnt start/run smoothly. especially at slow speeds in the range or 300 RPM

After 500RPM, the motor runs fine.

Thanks,

Needhu

  • 0
    TI__Guru 65220 points
    Needhu,

    Sensorless implementation is tough to spin at lower speeds. A 4-pole motor spinning at 300 RPM has an electrical frequency of 10Hz, very tough to implement.

    At 500 RPM, the same setup has an electrical frequency of closer to 20Hz, still tough but easier than 10Hz.

    To spin this slow reliably the customer should use a higher pole motor (for example an 8 pole motor would give them half the RPM for the same electrical frequency) or they should use Sensored control.

    Regards,

    -Adam