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Unexpected phenomena at offset estimation and error during Rs estimation

Haneol Park
Prodigy 140 points


I'm doing developing a 200HP VFD based on my own PCB using F28069M and inverter stack.

I'm trying to proceed motor identification using IstaSPIN. But now I'm suffering from an unexpected phenomena at offset estimation stage.

As you can see, there is an unexpected current at offset estimation stage. At very first time of my test, I couldn't see that one.

But I saw those phenomena today morning and Rs estimation stops without any error since I saw that situation as you can see from CH2 of the oscilloscope.

I didn't do any revision of the source code. I also believe that there was any other change in H/W.

I could hear a noise when those switched current occurred at offset estimation stage, which I had haven't been able to hear before.

Could you please help me to solve this problem?

  • 0
    TI__Guru** 116090 points

    Hi Haneol,

    Maybe, you need to check the current signal sample circuit. The estimator state is EST_State_Rs, passed CTRL_State_OffLine state to measure the offset, and passed EST_State_RoverL to do R/L estimation. Both states didn't need current using voltage control only. You met the problem when the EST_State_Rs state need current close loop control, so you have to check your hardware to confirm the current signal sample is correct.

    Best Regards,

    Yanming Luo

  • 0 in reply to Yanming Luo
    TI__Guru** 119670 points
    I would especially check the polarity of the current signal as discussed in SPRHUHJ1 chapter 5
  • 0 in reply to ChrisClearman
    Prodigy 140 points

    Hi Chris,

    Thank you for your answer.

    The polarity is definitely correct cuz I already checked its validity by comparing scope waveform to CCS graph waveform.

    By the way, I realized that the phenomena occur when DSP runs for tens of minutes.

    So I checked the board temperature thru thermal image camera. DSP and other components seemed OK.

    But I found that a voltage divider circuit composed of some chip resistors, which is directly connected to ADC channel of the DSP, show very high temperature exceeding one hundred degC. I feel that I chose too small resistor value and it might make the abnormal operation of the DSP because I didn't use isolation between the inverter stack and the DSP as TI HV motor kit. Do you think this trouble can make the issue?

    Regards,

    Haneol

  • 0 in reply to Haneol Park
    TI__Guru** 119670 points
    isolation isn't necessary but it certainly seems like there is something wrong with this circuit.