Sensorless Position Control of Induction Motors

Concepts for sensorless position control of induction motor drives rely on anisotropic properties of the machine rotor. Such anisotropies can be incorporated as periodic variations of magnetic saliencies in various ways. The built-in spatial anisotropy is detected by in- jecting a high-frequency flux wave into the stator. The resulting stator current harmonics contain frequency com- ponents that depend on the rotor position. Models of the rotor saliency serve to extract the rotor position signal using phase-locked loop techniques. A different approach makes use of the parasitic ef- fects that originate from the discrete winding structure of a cage rotor. It has the merit of providing high spatial resolution for incremental positioning without sensor. The practical implementation of sensorless position identifi- cation, and of a high-accuracy position control system are

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