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28027F InstaSPIN cut off frequency

Daniel Fang
Genius 11600 points

Other Parts Discussed in Thread: DRV8312

According InstaSPIN FOC user guide, if set cut off frequency to 1.6K, it will affect the phase current waveform. Use 0.1uF capacitor and set cut off frequency to 358Hz,  phase current waveform is OK. (The max phase voltage is 900Hz, so set cut off frequency to 358HZ is incorrect.


Actual test:
According to the user guide to adjust cap to 22nF, cut-off frequency is 1626.545hz.

Transient current distortion is serious.
After adjustment:

Not adjusted: cut off frequency is 385HZ, cap is 0.1uF.

  • 0
    TI__Guru** 119680 points
    you should set your phase voltage filter frequency to 300-400 Hz and update the software variable to match in user.h
  • 0 in reply to ChrisClearman
    TI__Genius 11600 points
    Hi ChrisClearman,

    1. Do you mean that set cut off frequency to 300 - 400HZ, no matter the kind of motor, regardless of the voltage frequency?

    2. The feedback three phase voltage, enter in EST estimation after the Clark conversion, which parameters are involved to estimated, what's the effect, because this part of theory and software is not open.

    3. The max motor speed is about 6000rpm, 11 pairs of poles, the highest voltage frequency is 1.1KHz. It has impact on phase current when set cut off frequency to 1.6K , impact is very small if set to 385Hz.
  • 0 in reply to Daniel Fang
    TI__Guru** 119680 points
    1. Yes. We are going to update SPRUHJ1 on this topic. You will notice on all of the EVMs except for DRV8312 we have poles in the 300-400 Hz range. While there are some slight benefits to using a higher pole for high frequency motors, as the pole increases it can be more effected by drift of components and differences between the channels. We have not seen any issues with using a pole value ~4 times lower than the maximum frequency. So our recommendation - in the user.h xls - is to choose a value between 200 and 400 Hz, with the minimum being 200 Hz or max_freq_hz / 4.

    2. the phase voltages and currents are used in the estimation. we don't go into details.

    3. For your motor the minimum would be 275 Hz pole, but I would choose one in the 350-400Hz range.