Speed measurement of inverter fed induction motors using the FFT and the rotor slot harmonics

This paper focuses on the advantages and limitations of speed measurement of induction motors using spectral estimation of the rotor slot harmonics present in the line current, The proposed method provides real-time, accurate rotor speed measurement using FFT-based spectral estimation. The accuracy of the FFT is enhanced using an interpolation algorithm. Furthermore, a recursive speed calculator is presented using short-time FFT. Using this calculator, speed transient results are presented and discussed