Design of Ladder-Slit Secondaries and Performance Improvement of Linear Induction Motors for Urban Rail Transit

In order to improve the performance of linear induction motors for urban rail transit, the ladder-slit secondary is designed, and the performance of linear induction motors with the ladder-slit and flat-solid secondary is calculated and compared. First, for the ladder-slit secondary, the slot combination, widths of the secondary conductor, and side bar are designed. Second, the finite-element model of the linear induction motor with the ladder-slit secondary is developed, and the influence of vertical forces on widths of secondary conductors is presented. Third, the eddy current and the transversal air-gap flux density are compared when the ladder-slit and flat-solid secondaries are applied, respectively. Finally, experiments are carried out by test lines to validate the calculated results of the force and efficiency. It shows that the ladder-slit secondary can reduce the edge effect and improve the performance.