Speed-sensorless torque control of induction machine based on carrier signal injection and smooth-air-gap induction machine model

A speed-estimation technique for induction machines, based on carrier signal injection and the standard two-axis smooth-air-gap induction machine model, is presented. The proposed speed-estimation technique can work over a wide range of operating points, including fundamental dc excitation. The stability of the algorithm is analyzed using a two-time-scale approach. Based on the estimated rotor speed, a torque controller is designed. Experimental results are presented confirming the validity of this approach. A method to reduce torque ripple generated by the injected carrier signals is also introduced