How to calculate PMSM real phase current?

  from proj_lab10

// calculate vector Is in amps
  gMotorVars.Is_A = _IQsqrt(_IQmpy(gMotorVars.Id_A, gMotorVars.Id_A) + _IQmpy(gMotorVars.Iq_A, gMotorVars.Iq_A));

This is what you can calculate with Id and Iq, but this isn't the instantaneous phase current, it's the length of the current vector in the D-Q reference frame.

Thanks ,

ChrisClearman,

My project is " DRV8312-C2-KIT_v128 (PM_Sensorless)" ,so if Id = _IQ(0)，Iq = _IQ(0.1)，

then " Is = _IQsqrt(Id ^2 + Iq^2)", so how to change "is" to real Phase current?

To get phase currents from Id and Iq, you will have to do inverse Park followed by Inverse Clarke Transform. This is already done in the project on Vd and Vq variables to get phase voltages.

rgds,

ramesh

Hi,

If i know the following the parameters:

(1) id and iq value(IQ format)

(2) Current sample resistance  :  0.05Ω

(3) Amplifier enlargement factor :  4

and how to get real phase current ?

thanks !

If ADC input range is 0-3.3V, then midpoint voltage is 1.65V, corresponding to zero current. 1.0pu input to ADC will be 1.65V. With an amplifier gain of 4, and Rsh=0.05,

then 1.0pu shunt current (that produces 1.0pu voltage input to ADC) ==> (1.65V / 4) / 0.05 = 8.25A

If you scale the sw such that _IQ(1.0) corresponds to 3.3V at ADC input, then it corresponds to 8.25A positive current and 0V at ADC input will correspond to 8.25A negative current or viceversa.

rgds,

ramesh

thanks,

ramesh,

just as you said , it is the instantaneous phase current.

so if I want real RMS (phase current), the formula is :

Imax = 8.25 * _IQsqrt(Id ^2 + Iq^2), and :

Irms = Imax / sqrt(2)

is it right?

Look forward to your reply !

thank you!

Yes