Rotor Resistance Adaptation for Sensorless Vector Controlled Induction Machines

Abstract

The vector control method is widely used for induction motor drives. In these applications, a rotational transducer such as a shaft encoder is used. A rotational transducer, however, cannot be mounted in some cases such as motor drives in a hostile environment, high speed motor drives, etc. Several sensorless vector controlled induction machine drive methods have been proposed. These methods have a disadvantage that the rotor resistance variation causes the estimation error of the motor speed. It is difficult to estimate the motor speed and the rotor resistance simultaneously, because the equivalent rotor resistance is the ratio between the rotor resistance and the slip under steady states. Therefore, we have proposed a method of estimating simultaneously the motor speed and the rotor resistance of an induction motor by superimposing AC components on the field current command. This paper presents a modified method of the rotor resistance adptation. The validity of the proposed method is verified by the experimentation.