The FEM Numerical Analysis Of Superconducting Levitation System And It's Application In Small Wind-drag Generator

The flux pinning effect of the type-II superconductor can make a permanent magnet stable levitated on the superconductors. This levitation system can be used in making maglev trains, suspension bearings, antigravity field equipments and et, al. This paper mainly describes the application of YBCO superconductors in superconducting levitation bearings.The eddy currents will be induced in the superconductors when the permanent magnet is moved close to the superconductors. Because the superconductor is non linear material which conductivity is not constant, it is very difficult to calculate the current distribution in the superconductors. The Kim model and field flux creep-flow model are adopted to establish the constructive equations of the superconductor.The current vector potential is an important auxiliary variable in numerical analysis of eddy current field. Through this method, the current field is changed into current potential vector field. When the current potential vectors are subjected to some boundary conditions, the differential equation is established in the superconductor-permanent magnet system.The differential equation of the current vector potential is solved by Galerkin finite element method. The differential equation is firstly changed into integral equation. The continuous integral equation is changed into discrete equation at time and space. According to axial symmetry, the space lattice of the cylinder superconductor can be transformed into 2D plane grids. The 2D plane is divided by triangular elements. The elements and nodes are given numbers. Any current vector potential of a point in an element can be expressed by the values of the nodes using linear interpolation method. Adopting the Galerkin method, the linear equations group is established in every element.An integral linear equations group of whole superconductor is formed by assembling all the element equations. The current vector potential of every node can be calculated through solving this linear equation group. The current potential vector distribution is obtained. The external magnetic field is calculated by finite element method soft.The current density distribution is calculated according to the current vector potential distribution. The interaction force between superconductor and permanent magnet can be known. The results of numerical analysis results are constant with the experimental results.Under zero field cooling condition, the permanent magnet is moved to and from the superconductors between infinite distance and superconductors. In this procedure, the levitation force-displacement curve presents hysteretic phenomenon. At the same position, the levitation force value is relevant to the permanent moving history.Under the field cooling condition, the permanent magnet can stably suspend on the superconductors. This stability position is the lowest energy of the whole system. When the external force is acted on the permanent magnet, the permanent magnet deviate from the balancing point, the restoring force will drag the permanent magnet to the original position. The value of the restoring force is relevant to magnetic flux density, magnetic field gradient, levitation height and relative area ratio between superconductors and permanent magnet. If the displacement of the deviation is small, the processing magnet presents a comparison to the spring with damping. Using numerical analysis method, the magnitude, frequency and damping factor can be calculated.Wind energy source is a trend of pollution-free energy in the future. A new type wind drag generator model and its experimental instrument are discrebed in this paper The superconducting levitation system can be used in small wind-driven generator to generate electricity. Because of non-contact of the bearing; small wind can drive the generator to transform wind energy to mechanical energy. At no-wind time, the generator is a power storage flywheel. The utilization ratio of wind energy is larger than traditional wind generator.The influencing factors of rotation losses include levitate height, aerodynamic losses, damping losses and eddy current losses and et, al.The stability of the shaft is very important factor in levitating energy system. This paper discussed the influenceing factors of the stability of the shaft and gave some advice to solve this problem. The arrangement of the superconductors, levitate height, rotational speed and installation accuracy are important for the stability of the shaft.A new large-scale superconducting levitation model is presented in this paper. This model is not limited by the size of superconductors.The superconducting levitation system is used in small wind-driven generators can increase largely efficiency of wind-drag generator. It must be a new important member in clear energy sources in the future.