Signal processing for determining flux and torque of induction motors

The authors deal with an indirect signal processing method for determining the flux components and the electromagnetic torque. The method utilizes the input voltage and current signals in order to obtain the derivatives of the stator flux. These derivatives are then transformed in the frequency domain by means of fast Fourier transforms and are successively integrated in the same domain. The implementation of the inverse FFT permits the flux components in the time domain to be determined and the electromagnetic torque to be monitored. The results are very accurate because the technique of Fourier analysis is the most suitable for examining signals rich in harmonics such as the output voltages of the inverters