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 or high-speed motor drives. Several sensorless vector-controlled induction machine drive methods have been proposed. These methods have the disadvantage that rotor resistance variation causes errors in the estimation 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 of the rotor resistance to the slip at steady state. Therefore, we have proposed a method of simultaneously estimating 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 adaptation. The validity of the proposed method is verified by experiments. © 1998 Scripta Technica, Electr Eng Jpn, 125(2): 65–72, 1998