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Tham khảo tài liệu 'applications of high tc superconductivity part 8', kỹ thuật - công nghệ, cơ khí - chế tạo máy phục vụ nhu cầu học tập, nghiên cứu và làm việc hiệu quả | 3-D Finite-Element Modelling of a Maglev System using Bulk High-Tc Superconductor and its Application 129 Step 6 t t At until the maximum number of time step is achieved and the steps 2-5 are repeated. 3.4 Numerical precision Based on a levitation system composed of a bulk high-Tc superconductor single-domain with a cubical shape and magnetic rail assembled by the permanent magnets with opposite magnetization direction as shown in the inset of Fig. 2 the dependence of the computational precision of the levitation force on both mesh density and time step is discussed in this section. In the calculation the bulk high-Tc superconductor was downward in a speed of 1 mm s from the filed cooling position to the nearest gap and then upward to its original position. On the basis of the geometrical and material parameters listed in Table 2 and power law model the levitation force of the bulk high-Tc superconductor was calculated in this vertical down-and-up movement with different mesh densities and time steps. Wsc mm lsC mm tsC mm J A m2 1 V m U eV a 10 10 10 2.5x108 1x10-4 0.1 3 Table 2. Parameters of high-Tc superconductor used in the calculation for investigating the numerical precision. Fig. 2 shows the dependence of the levitation force versus gap curve and the maximum levitation force Fmax at the nearest gap on the total finite element node. This figure clearly illustrates that the levitation force and its hysteresis behavior will approach to a saturated state with the continuous increment of the total finite element node or in other words the continuous increment of the mesh density. It can be seen from the inset that the Fmax continuously increases with the total finite element node but the increased rate is gradually Fig. 2. Levitation force versus gap with different total nodes and the maximum levitation force Fmax as a function of the total finite element node inset . 130 Applications of High-Tc Superconductivity Fig. 3. Levitation force versus gap with different
