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DRV8301-69M-KIT: InstaSpin FOC - SVM Modulation questions

Paul LaRue
Prodigy 70 points
Part Number: DRV8301-69M-KIT


Hello!

I was hoping I could get some clarification of the SVM Modulation tab within the InstaSpin FOC GUI under "Advanced: Field Control & Modulation". It is set by default to 1.15. I only have a cursory understanding of SVM so can someone explain the difference between setting the duty cycle to say 1.00 (perfect sine) or 1.33 (max trapezoid)? 

I saw from this post that the current technique used in the code does not decrease switching losses over sinusoidal modulation, but there is a technique to keep one phase LOW for 120deg and reduce swicthing losses by 33%. Is this is possible to implement easily using the InstaSpin FOC GUI by changing the SVM modulation setting? Any advice is greatly appreciated. 

Thank you,

Paul

  • 0
    TI__Guru** 116210 points
    1. SVPWM can increase the linear region by 1.1547 times (2/SQRT(2)) for the maximum possible output voltage. The 1.0, 1.15 and 1.33 in InstaSPIN-FOC are for over-modulation that means the ratio of the fundamental voltage applied to the fundamental voltage. You have to apply a current reconstruction scheme if you are using shunt resistors on the low side for current sensing as InstaSPIN-FOC EVM kits.

    2. You can't do this via GUI, you have to change SVGEN code to support this modulation method which generally names 5-segment SVM or discontinuous PWM (DPWM). You might find many papers about this in IEEE or other websites.