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InstaSPIN-FOC/FAST questions

Eric Phillips
Prodigy 50 points

I'm researching whether the C2000 microcontrollers (specifically the F28004x series) are a good fit for a project utilizing BLDC motors that I am currently working on.  I had two quick questions after reviewing users guides, training videos, and forums.

- In the InstaSPIN User’s Guide, it states "FAST requires 2-phase currents (3 for 100% over-modulation)..." - is the 100% over-modulation just to utilize space-vector schemes?

- In order to utilize the FAST encoders, does the DC bus voltage of the motor have be monitored (i.e. sent to an on-board ADC) or is it optional?

Thanks.

  • 0
    TI__Genius 17175 points
    Hi Eric

    In the case of over-modulation, the FAST estimator uses an algorithm to ignore 1- or 2-shunt measurements and extrapolates the values instead using math or an averaging formula. You'll need 3 phase current shunts in order to perform the highest possible output from over-modulation. On recent examples though, we strongly suggest to limit the modulation index to only ignore 1-shunt measurement instead of 2 as the performance when ignoring 2-shunts is greatly decreased

    Yes, FAST requires the DC Bus voltage to be monitored, you cannot skip this ADC connection

    Sean