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TMS320F28069F: a question on the performance of InstaSPIN FOC for an ACIM

Jeongsoo Yoo
Expert 1025 points
Part Number: TMS320F28069F


Hello,

I have a question on the performance of InstaSPIN FOC for an ACIM.

Last month we have carried out a dynamometer test on our 1.5kW ACIM: its rated speed is 1760 RPM and its rated torque is around 8.0 Nm.

Our inverter runs on the basis of Lab10c with the overmodulation function.

A summary of the test is as follows:

(1) The measured output torque is larger than the rated torque up to the motor speed of 1950 RPM.

(2) At 2100 RPM, the measured output torque is around 6.0 Nm.

(3) At 2190 RPM, the measured output torque is around 0.8 Nm.

Therefore it is observed that the output torque is diminished abruptly beyond 2100RPM.

Is this result normal in terms of the performance of InstaSPIN FOC for an ACIM?

Please review this test result for us.

Thank you for your guidance.

With regards,

JS Yoo

  • 0
    TI__Guru** 116090 points

    That should be a normal testing result for an ACIM using a sensorless FOC. The torque current is limited to the dc bus voltage since the most voltage is applied to generate the magnetizing current when the speed is higher than the rated speed and the motor works in constant power region.
    .

  • 0 in reply to Yanming Luo
    Expert 1025 points

    Hi Yanming Luo,

    Thank you for your review.

    My collegue told me that a V/F control might be better than the sensorless FOC when the motor speed is higher than the rated speed for an ACIM.

    In other words, the V/F control would provide more torque than the sensorless FOC when the motor speed is higher than the rated speed for an ACIM.

    Why is it so?

    Thank you for your guidance.

    With regards,

    JS Yoo

  • 0 in reply to Jeongsoo Yoo
    TI__Guru** 116090 points

    The advantage of the V/F control doesn't need precise motor parameters, and it's easy to implement. The sensorless FOC should have better performance in full speed range than it if the motor parameters are precise, but you have to tune the FOC algorithm to consider the changing parameters and add field weakening control high speed over the rated value.

  • 0 in reply to Yanming Luo
    Expert 1025 points

    Hi Yanming Luo,

    Thank you for your review.

    I understand from your reply that I need to do two more works as follow:

    (1) I have to tune the FOC algorithm to consider the changing parameters.

    --> I have already applied the InstaSPIN function of Rs online recalibration for the dynamo test. What are the other functions of InstaSPIN that I need to consider for this issue?

    (2) I have to add field weakening control at high speeds over the rated value.

    --> In my previous post, I made a question on the field weakening control for an ACIM and you replied that the field weakening control was tested only for PMSMs and it is not recommended for ACIMs. Our motor is a 1.5kW ACIM as mentioned in this post. May I add field weakening control at high speeds over the rated value for our 1.5kW ACIM?

    Thank you for your guidance.

    With regards,

    JS Yoo

    ]

  • 0 in reply to Jeongsoo Yoo
    TI__Guru** 116090 points

    (1) We don't recommend and implement Rs online for ACIM since a non-zero Id must be applied to the motor always, you may try it yourself.

    (2) As repled above, yes, you need to add the FWC. We can just give you some advice, but we didn't test it on a real motor.

  • 0 in reply to Yanming Luo
    Expert 1025 points

    Hi Yanming Luo,

    Thank you for your review.

    I acknowledge that I need the FWC for induction motors.

    When are you planning to add the function of the FWC for induction motors to InstaSPIN?

    Thank you for your guidance.

    With regards,

    JS Yoo

  • 0 in reply to Jeongsoo Yoo
    TI__Guru** 116090 points

    Not any plan yet since it's not necessary for most ACI motor applications.

  • 0 in reply to Yanming Luo
    Expert 1025 points

    Hi Yanming Luo,

    Thank you for your review.

    Let me close this post.

    With regards,

    JS Yoo