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Space Vector Voltage Ripple

RLetizia
Intellectual 990 points

I'm seeing what looks like a 120-135 Hz ripple on the SVM motor phase voltage.

See the two phase voltage images below.  The data is raw ADC values, saved in mainISR every 250 usec sample.  The motor is running at 100 RPM or 3.3 Hz. The second image zooms in on the first image and shows the ripple frequency.    For example, there are voltage peaks at points 344,375 & 405, which at 250 usec/sample puts the ripple peaks at ~133 Hz.

The corresponding phase current signal shows very-very little ripple.

The design is based on the HV kit and this is an ACIM motor.    Our phase voltage filtering is greater than the HV kit with the pole at 221.1 Hz.  USER_VOLTAGE_FILTER_POLE_Hz    (221.1)

The motor is running OK, but I trying to understand if this ripple is normal and where it is coming from?

Would this ripple negatively effect the angle and slip estimation?

Thanks.

 

  • 0
    Intellectual 990 points
    After looking at his closer, it looks like the frequency corresponds to the DC Bus ripple. This is a single phase 60 Hz bridge rectifier, so the ripple is bus ripple is 60Hz x 2 = 120 Hz.

    Our DC bus ripple is about 3V (3V/325V= ~1%).

    Does the fact that the current signal looks good and the ripple is only seen in the SVM voltage indicate that that the 1/DC Bus compensation algorithm is doing its job and working correctly?

    Or if the 1/DC bus compensation is working , should there be no ripple on the SVM voltage?

    Thanks for helping me understand this.
  • 0 in reply to RLetizia
    TI__Guru** 118270 points
    we will take a look and give you our thoughts.
  • 0 in reply to ChrisClearman
    TI__Mastermind 27240 points

    The DC bus ripple is being compensated for ripples and that is why you see its foot print on the compensated voltage. When you look at the final output voltage (inverter ouput), it should be free of ripples.  

    rgds,

    ramesh