A Study on Optimal Operating Point of Linear Induction Motor Considering Normal Force and Efficiency in MAGLEV Vehicle

This paper presents the electromagnetic characteristics of a linear induction motor (LIM) for a semi-high-speed magnetic levitation or maglev vehicle. The propulsion system of the maglev train provides excellent ride quality, but still has a disadvantage in that the propulsion efficiency is low owing to its inherent characteristics. In particular, in the propulsion system of maglev trains with a relatively large air gap, the increase in the propulsion efficiency remains an important issue. The propulsion system generates a vertical force during propulsion control. To ensure the stability of the propulsion system, the electromagnetic characteristics of the propulsion system's vertical force need to be interpreted accurately. The normal force and thrust are analyzed with the finite-element method considering the varying speed and slip. To improve the propulsion efficiency, variable slip-frequency operation is proposed without deteriorating the levitation performance. The thrust map of the LIM with allowable slip frequency is also presented.