Investigation of a low-speed single-side HTS linear induction motor with different primary structures used for linear metro

This paper presents the influence of the primary structures on the performance parameters and critical current of a low-speed single-sided higherature superconducting linear induction motor used for the linear metro system. Three types of the primary structures, namely, a slotted iron core, a slotless iron core, and an air core, are set up to evaluate the influence. Developed by the Ag-sheathed Bi-2223 tapes, the exciting windings are distributed with a double-layer concentrated structure. The correction factors and the transverse coefficient are presented to consider the transverse edge effects. The 2-D mathematical model considering the longitudinal end effects is established, and the boundary conditions are given. The transient electromagnetic field of the three schemes is solved by using the time-stepping finite-element method. The experiment carried out on a prototype with a slotted iron core is conducted to validate the accuracy of the established model. The flux density and the performance parameters such as the force characteristics, specific loss, power factor, efficiency, etc., of the machines with three versions of primary structures are compared and analyzed. In addition, the influence of primary structures on the critical current is also investigated.