A research on design method and theoretical analysis of electromagnetic suspension system considering magnetic interface between coils

This paper deals with the design and operating characteristics analysis of electromagnetic suspension (EMS) system. The EMS system consists of a rail, a U-shaped iron core, a high temperature superconductor (HTS) coil, a couple of DC control coils. The HTS coil generates a high magnetic field in the U-shaped iron coil and the rail. As wall as, the U-shaped iron core can be attracted by the coupled high magnetic field. We calculated turns and operating current conditions of HTS coil considering the decay of critical current when perpendicular magnetic fields are applied to the HTS coil. In addition to the design of the HTS coil, a Linear Quadratic (LQ) control method used to design the DC control coils that control the gap distance between the rail and U-shaped iron core. That is, if the gap distance is varied due to the several external disturbances, the DC control coils generated a magnetic field and then keep the constant interval. Thus, the operation of DC control coils would affect the magnetic flux density at the air gap. In this study, we verified the effect of distributions of magnetic flux density using finite element method (FEM) and MATLAB Simulink simulations. Furthermore, we numerically calculated the appropriate control current of DC control coils and the perpendicular magnetic field density on the HTS coil under the external disturbance. Based on these results, the appropriately combined current conditions and control method of EMS system to realize the stable levitation force were achieved.