A new method to reduce end effect of linear induction motor

Abstract

A new method to compensate the end effect of a linear induction motor (LIM) in low-speed maglev vehicles is proposed. With this method, the motors are close to each other so that the front motor's exit-end magnetic field extends into the next motor's entry zone. As a result, the motor's magnetic field traveling wave become continuous and the end effect of short primary LIMs is greatly weakened. In the analysis of the air-gap magnetic field distribution, the LIM is assumedly divided into two identical motors with the distances of 20, 40, 60, and 80 mm. The results show that the air-gap magnetic field is still continuous within these distances due to LIM's end effect. As the distance between two motors increases, the distortion of the air-gap magnetic field becomes more severe. Then, we investigate the relationship between the secondary speed and the thrust in three cases, i.e., a single LIM, two motors divided with 72 mm with pole pitch corrected, and two motors divided with 60 mm without the pole pitch being corrected. We find that the thrust has a small decrease when the speed increases, which means that the magnetic field is already continuous and its amplitude is approximately a constant. Furthermore, the thrust loss of case 3 is more than that of case 2, which indicates that the pole pitch correction is effective.