Rotor Speed Estimation Using Zero-Crossing Times Signal of Stator Current

The purpose of this study is to illustrate a new method for sensorless vector control of induction motors. This approach uses Zero-Crossing Times (ZCT) signal of stator current to estimate rotor speed. ZCT signal contains useful information which can be used for estimation of rotor speed and resistance. We have used this information for online estimation of rotor speed. To avoid time consuming fast Fourier transformation (FFT) analysis of ZCT signal, we have used switchable high order Butterworth Filters in order to extract rotor frequency. Simulation result has expressed good performance of this simple and inexpensive sensorless vector control of induction motors.