Three-dimensional finite element analysis of linear induction motors with a skewed ladder-type secondary

The slot harmonics produce a cogging torque and a crawling in a linear induction motor (LIM) with a ladder type rotor. To avoid those defects, we sometimes adopt the V-skewed rotor (or stator) which rise no lateral force. In this paper, we investigate the skew effect by the three-dimensional finite element analysis with A-φ method and specify significant points for adopting skewed slots. Based on the above approach, we evaluate the skew effect in the LIM, comparing it with the experimental data to confirm the validity of the analysis. The follows are confirmed: (1) the improvement of the cogging torque by introducing V-skewed rotor; (2) the decrease in the thrust force and increase in the sucking force as making the skew angle bigger, and the abnormal temperature rising in V-skewed rotor; (3) the decrease of the abnormal temperature rising by optimizing the shape of rotor; (4) the validity of the skewed stator for short stator machines. And we propose a method that put two stators skewed in the opposite direction to each other for the double-sided LIM.