• State
  • Locked Locked
  • Replies 2 replies
  • Subscribers 81 subscribers
  • Views 856 views
  • Users 0 members are here
Support feedback
Options
Options
Similar topics

This thread has been locked.

If you have a related question, please click the "Ask a related question" button in the top right corner. The newly created question will be automatically linked to this question.

HVMotorCtrl+PfcKit_v1.6 > HVPM_Sensorless_28335 > triangular waveform

kevin ***
Prodigy 230 points
Other Parts Discussed in Thread: CONTROLSUITE

Hi,

BACKGROUND

I am running

C:\TI\controlSUITE\development_kits\HVMotorCtrl+PfcKit_v1.6\HVPM_Sensorless_2833x\HVPM_Sensorless.c

on a eZdsp 28335 platform using CSv4

I have the following problem with the PWM output (I've been using build level 1 and 2)

PROBLEM

Setting VDtesting 0.5 (beautiful 3 phase space vector switching pattern 120 degrees phase seperation- observed via low pass filter RC)

Setting VDtesting to 0 (I would expect the PWM to be OFF - no demand).  however I see a slow triangular waveform on all 3 phases (all in phase).  It's period is 1.3seconds and its magnitude is 1.25V (on a 5V rail).  

When Viewing the PWM output with VdTesting =0.5, with a longer time base the whole switching waveform is mapped onto this slow 1.3s carrier wave.

NOTE

I'm running the PWM with a base of 5kHz instead of 10kHz.

....

Answer would make my Christmas...probably my year.

Thanks.

  • 0
    Prodigy 100 points

    Hello,

    From the looks of it I would say plot 1 suffers from aliasing.

    The actual triangle period should be 1/3 of the signal period (or the frequency 3x the signal frequency.) I doubt the triangle period is 1.3 sec (zoom in on the time axis).

    If the signals in plot 3 are not what you expect, you should learn about space vector modulation. It is a method to increase differential output  by adding a common mode   (the motor only cares about the difference between the 3 wires and thus does not see the common mode) 3rd harmonic to the output phases.

    Paul

  • 0 in reply to Paul van der Hulst39
    Prodigy 230 points

    Plot 3 is what I expect.  But this is mapped onto this slow moving 1.3second triangle wave modulated at 5 kHz.  The result is that plot 3 is offset over 1.3seconds added a shift onto the duty cycle.  Thus I cannot hold a steady state current in any of the phases.