Reduction on Longitudinal End Effect of High-Speed-Maglev DC-Excited Linear Synchronous Motors

The DC-excited linear synchronous motor (DCELSM) is one of the major types of electrical machine used in high-speed maglev trains. But the longitudinal end effect is a flaw that may cause side effects such as over-saturation due to the structure of linear machines. To suppress the longitudinal end effect, subsided end field-poles are usually adopted in real-world industrial applications. This paper proposes a theoretical model that takes the longitudinal end effect into account. Via the field analysis, the theoretical method to design the subsided end field-poles are established, as well as the estimation on thrust and levitation force by virtue of the subsidence distance of the end field-poles. Using the proposed theory, the end-field poles subsided by 28 mm are determined for a DCELSM utilised in a real-world maglev application. Besides, practical conclusions are obtained by further investigation into the air-gap field and electromagnetic forces in terms of the subsidence distance. The model and the analysis in this paper provide a general method to compensate for the longitudinal end effect in the DCELSMs.