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Original question:

CCS/LAUNCHXL-F28069M: Applicaton question about the instaspin-foc

CCS/LAUNCHXL-F28069M: Applicaton question about the instaspin-foc

ming chen3
Intellectual 775 points

Part Number: LAUNCHXL-F28069M

Tool/software: Code Composer Studio

hi,all.

I have ask a question about the application of instaspin-foc.

http://e2e.ti.com/support/microcontrollers/c2000/f/171/p/796645/2947434#2947434

but I still have some uncertainty about my application in instaspin.

please give me a help. thanks.

I still do not know how to calculate or estimate the motor wind Irms current according to the peak dc bus current 150A.
because I should use the motor Irms current to design my full current sensing scale .
the Irms is nothing to do with the Ibus in math?
or is there any design experience value between the Irms and the Ibus ?
the Irms = 2*Ibus or Irms = 3* Ibus ???


I wonder that whether the in-line current sensing is better than the shunt resistor current sensing method especially in current sensing precision ?
in my opinion，the peak current of in-line current sensing perhaps is bigger than the peak current of the low side shunt resistor current sensing method. so the full current scale in in-line mode is bigger than the shunt resistor .
in such a big current ,it is difficult to select a suitable Rshunt（value Ω and power W） in inline mode. 

if I use the in-line current sensing with an AMC1301,whether I need to change the instaspin current sensing program.
because the instaspin use the shunt resistor current sensing method.

thanks.
all the best .

  • 0
    TI__Guru** 117200 points
    1. The RMS current and voltage are not necessary for InstaSPIN or motor control. You might use the below formula to calculate these two value.
    Irms =sqrt((I1*I1+I2*I2+...+In*In)/N) where I1, I2...In are the sampling value in a period, N is the number of the sampling period that is related to the running frequency.
    2. Right, inline current sensing is much better than the shunt resistor. A low side shunt resistor is mostly used in low current and cost application. InstaSPIN can support both current sensing modes, and you don't need to change anything from the motor control algorithm side.