Design and Evaluation of Linear Primary Permanent Magnet Vernier Machines for Urban Railway Transportation

Linear induction machine (LIM) is used as a driving machine in urban railway transportation because of its simple structure and mature technology. However, low thrust force and efficiency have always been a difficult problem to be solved. In the last decade, linear primary permanent magnet vernier machine termed as LVM in this paper has been extensively investigated owing to its potential application prospect in urban railway transportation. However, there is a lack of investigation on the feasibility of rendering the LVM the same size as existing LIM used in urban railway transportation. Therefore, in this paper, a large-sized LVM is designed and evaluated according to the requirement. Firstly, the LIM used in practical urban railway transportation are introduced. Secondly, the LVMs with the same size as the LIM counterpart are established by finite element method. Then, effects of consequent-pole Halbach permanent magnet structure, secondary tooth number and primary slot shape on performances are investigated. Thirdly, a LVM is optimized and compared with the LIM. The results revealed that the LVM exhibits higher thrust force and efficiency. Finally, a small-sized prototype of LVM is constructed to validate the simulation.