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Original question:

TMS320F28027F: Lab20 to Lab11a Migration

TMS320F28027F: Lab20 vs Lab11 Efficiency

Noah Erickson
Prodigy 170 points
Part Number: TMS320F28027F


Hi E2E,

I recently migrated from Lab20 to Lab11a and am noticing a decrease in efficiency. I'm driving a motor at 19,000 RPM with a fan for a load. Lab20 only takes 23A of IQ current to reach 19,000 RPM but lab11a takes 25A of IQ current to reach 19,000 RPM.

We are using Motorware18 on a TMS320F28027F based custom motor controller. The screenshots below are taken from Lab20 and Lab11A respectively. Is there something I may be doing incorrectly? 

  • 0
    TI__Guru** 116350 points

    Do you enable the field weakening in both projects? Please check if the "USER_MAX_VS_MAG_PU" is the same in these two projects, and check if the torque reference current and feedback speed are different in these two projects.

  • 0 in reply to Yanming Luo
    Prodigy 170 points

    Hi Yanming,

    Thanks for the quick response.

    We do not use field weakening for either projects. USER_MAX_VS_MAG_PU is 0.5 for both projects since we are not using overmod. Feedback speed is 19,000 RPM for both projects since we are using speed control. IQ current references are of course different since lab11 is driving at a higher current. Anything else I should be checking?

    Thanks,

    Noah

  • 0 in reply to Noah Erickson
    TI__Guru** 116350 points

    Did you meet the same question at other reference speeds under the same running state? Or just at the maximum reference speed? What's the reference Id, Iq, Vd, and Vq in both project under the same testing condition? Both are current feedback control, which should have the same reference currents for the same load if the motor parameters are the same.

  • 0 in reply to Yanming Luo
    Prodigy 170 points

    Hi Yanming,

    I forgot to update this thread but we figured out a fix for the issue. Instead of getting the current measurement from the estimator like lab11 does I switched to using a Park transform like Lab20 uses. This reduces the IQ current by 2A at our max reference speed. My hunch is that we are somehow saturating a parameter in the estimator at higher speeds.

    Regards,

    Noah