# Induction motor - calculating rotor flux angle

1. Sep 9, 2017

### fasset

Hello.
I'm trying to write my own soft for Field Oriented Control of induction motor. I have finished hardware - 3ph 3kW inverter, controled by STM32F4, and V/F open loop algorithm to control ACIM - it works. Now I'm trying to implement FOC algorithm.
As we know we need to do Clark&Park transformation.
To calculate Park transformation it's necessary to know rotor angle flux position. Here some details:
ftp://ftp.ti.com/pub/dml/DMLrequest/Christy_FTP-10-30-12/controlSUITE/development_kits/HVMotorCtrl+PfcKit_v2.0/HVACI_Sensored/~Docs/Sensored%20FOC%20of%20ACI.pdf
Another note propose to use speed integration to do this:
http://tinyurl.com/y9lrb4cr
Could anyone expalin how to do this exactly?
I'm measuring currents (5kHz sampling), calculate Clark and also measure speed, slip.
Thanks for any response.

2. Sep 16, 2017

### Vitro

Hi @fasset, my BSc degree project was a sensorless IM-DTC. Had you asked this question 15 years ago I could have given you a precise answer, but that was the last time I did anything like that and now my answer is pretty much just a guess.

I would start with a simple assumption that the rotor field angle is some function $F(I_s, s)$ taking values from 0 to 90deg, $I_s$ being the stator current and $s$ the slip. You may need an additional parameter for $F$ which is the frequency of the stator current. At slip 0 the angle must also be 0, and the motor should stall when the angle tries to go over 90 (max torque). So starting there you can try to empirically work out what $F$ is. Run the motor with a few fixed stator current values applying load to the shaft until it stalls. Make some plots of torque vs slip (do you have a torque transducer?). The torque is the cross product of the stator and rotor field vectors.

Of course you can just find the answer in the literature but the above is more fun :)

3. Sep 17, 2017