Sensorless speed control of an induction motor with no influence of resistance variation

Many speed sensorless vector control systems of induction motors have been developed. However, the speed control characteristics are affected by machine temperature variations, because these methods use the primary and the secondary resistance value to estimate the rotor speed. This paper describes the method of the primary and the secondary resistance estimation for speed sensorless control systems. The primary resistance estimation uses the secondary flux which is calculated by the instantaneous reactive power. On the other hand, the secondary resistance is directly calculated by the line voltage and the current without speed sensors. This method is possible on the PWM inverter fed induction motor. By combining these two methods, the speed control characteristic is robust to the machine temperature variations. The feasibility of these methods was verified by some simulation and experimental results. In the tested system, the compensation of the primary and the secondary resistance mismatching is achieved