Measuring active power for a converter fed induction machine

The power measurement by acquisition systems and FFT transform can be subject of uncontrolled errors because of intrinsic properties of Fourier transform. The paper proposes a correction method based on the best evaluation of the fundamental frequency and calculation of the fundamental RMS for voltage and current as well as their phase by using the definitions of these quantities. To validate the method we made virtual experiments on generated signals and laboratory measurements with different forms of currents obtained by feeding the circuits with different voltages. There is a good agreement of measurements and calculated values.