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3-shunt current measurement

Ronnie
Intellectual 750 points

It is well known that the low side shunt resistor carries current only when the low side PWM is ON when using shunt to measure current.

Is the sample time the moment three low sides PWM are ON or any one low side PWM is ON ?

If the sample time is the moment three low sides PWM are ON, how to ensure that in software?

  • 0
    TI__Guru** 114310 points
    To do current sample during 3 low side PWMs are ON. Please refer to spruhj1f.pdf (InstaSPIN-FOC and InstaSPIN-MOTION User's Guide) and InstaSPIN lab10a to find more detail description.
  • 0 in reply to Yanming Luo
    Intellectual 750 points
    Thanks for your reply!
    I have read spruhj1f.pdf (InstaSPIN-FOC and InstaSPIN-MOTION User's Guide) and InstaSPIN lab10a , lab 10a is about over-modulation and current reconstruction, I know if the max voltage vector is large enough, it needs current reconstruction. But my confusion is that how software can ensure every current sample moment happens at 3 low side PWMs are ON.
  • 0 in reply to Yanming Luo
    TI__Guru** 114310 points
    The 3 low side is on in the same time when the output duty is not 100%. Please refer to SPWM or SVPWM document which can be find in TI web or other we also.