Induction motor sensorless control based on a maximum torque per ampere approach

The paper proposes a new position sensorless control approach for induction motor drives able to generate correct field orientation through continuous minimization of the stator current amplitude, holding the system in a maximum torque per ampere state. In such conditions an estimation of the angular position of the rotor flux, insensitive to rotor speed and motor parameter variations, is univocally carried out from the known angular position of the stator current. According to the proposed approach a sensorless field oriented control scheme with variable rotor flux amplitude has been developed featuring direct detection of the position of the rotor flux and working at very low stator frequency with no additional high frequency excitation. Experimental results are presented in order to evaluate the performance of the proposed approach in terms of dynamic response.