Open loop estimation models used in electrical drives systems

The low cost and high reliability of controlled induction motor drives without mechanical speed sensors made them to become more and more attractive. The information on the rotor speed is obtained from measured stator voltages and currents at the motor terminals with replace the sensor (mechanical sensor). Vector controlled drives require estimating the magnitude and spatial orientation of the fundamental magnetic flux waves in the stator or in the rotor. Open loop estimators are used for this purpose. Therefore, this paper is focused on the models of estimators of speed and flux useful in sensorless electrical drive systems. A speed estimator controlled by the stator voltage is proposed. The dynamical behavior of the system was analyzed by simulations performed using the Matlab/Simulink environment. Several experimental results are given in order to point out the proper operation of the estimators and the control strategy.