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TMS320F280049C: Instaspin speed estimation unstable

josep peng
Prodigy 30 points

Part Number: TMS320F280049C
Other Parts Discussed in Thread: TMS320F280049, TMS320F28069M, MOTORWARE

Hi

We use TMS320f280049 instaspin to estimate and control the speed of an induction motor. The motor is used in an elevator. We get the motor speed and flux angle from the estimator and perform vector control. 

We had two different behaviors in light and heavy load directions(the light load was in positive speed and heavy load was in negative speed). When we control Id at 13.5A(which is the rated magnetizing current of the motor measured in identification process), the speed estimation is ok in both directions but the maximum possible speed is 40Hz. If we reduce Id to 11A, everything is good in light load direction(speed estimation works ok, 45Hz is achieved, and the estimated flux varies between 1 to 1.2Wbs in different speeds) BUT in heavy direction, when the speed reaches around 30Hz, the speed estimation got unstable (varies continuously  between positive and negative more than 500Hz) and the estimated flux goes down to 0.2Wb  . 

Can you help us to find the cause of this problem?

Some points to note:

-We think the motor parameters such as Rs,Rr,Ls are measured with acceptable accuracy. 

-a typical elevator drive from a Chinese company works well with this elevator and controls the speed up to 50Hz in both directions.

-We update estInputData.speed_ref_Hz and estInputData.speed_int_Hz with reference speed (which can be positive or negative) before Est_run 

Thank you

  • 0
    TI__Guru** 117220 points

    Are you using your own board? If yes, please show the current and voltage sensing circuit, and the user.h.

    Which type of motor are you working on? It looks like it is an ACIM. Please note that we don't provide support for controlling the ACIM with instaspin-foc on F28004xC.

  • 0 in reply to Yanming Luo
    Prodigy 30 points

    The motor type is ACIM. You mean that instaspin-FOC on F280049C doesn't work on ACIM motors? 

    The voltage is estimated with PWM duty cycle multiplied by Vdc. The current is measured on the motor terminals via shunt resistors and isolated amplifiers. (i.e. the motor currents are measured not switch currents) . We have tested the current sense circuit and it has a very good response.

    We have tested the board on different ACIM motors. In all of them, if we reduce the d-axis current, speed estimation gets unstable, but the amount of reduction to cause instability is different. In the previous ones, if we reduce the current to about 0.6 nominal magnetizing current, instability happens which is not a problem because we only need maximum 30% field weakening to reach the desired speed, but in the mentioned last motor, only 2A reduction(about 15%) causes instability, and it has made us worried whether our product can be regarded as a general drive that works with all ACIM motors or not.

    The point is that it seems motor parameters have small influence on speed estimation. The reason is that on our first experiments on the previous motors, the default values loaded in user.h was very different from actual parameters of the motors, but the speed estimation worked well in both light load and heavy load down to 60% d-axis current.

    Can you please help us to find the reason of instability and make our product robust? 

  • 0 in reply to josep peng
    TI__Guru** 117220 points

    Correct. We don't recommend and test instaspin-foc on F28004x for ACIM, especially using field weakening control for ACIM.

    You have to tune the magnetizing current according to the running state and adding load.

  • 0 in reply to Yanming Luo
    Prodigy 30 points

    How about TMS320f28069M. Does it support ACIM and do you provide support for ACIM on it?

  • 0 in reply to josep peng
    TI__Guru** 117220 points

    Yes. You can use the example labs for F28069F/M in motorWare that supports ACIM.

    MotorWare

    http://www.ti.com/tool/motorware