Jipeng Li

Performance of a Small-Scale High Temperature Superconducting Linear Synchronous Motor Prototype

Four coils made of YBCO-coated conductor wire were fabricated and connected in series to make up the excitation system of a linear synchronous motor system with a stator made of ordinary copper wire. The electromagnetic forces experienced by the superconducting coils with respect to the stator were studied in the static case. We began with the study of one single coil, followed by two coils connected in series, and finally, four coils in series from which the largest force obtained was of 53.9 N at a gap of 10 mm at 77 K. The critical current, n-value, and inductance were also measured for the coils so that the power dissipation of the field windings can be calculated. This paper also helps us understand whether linear motors with superconducting components are currently economically feasible with present commercially available superconducting wire.

Vibration Characteristics of the HTS Maglev Vehicle Running on a 45-m-Long Ring Test Line

With further studies of high-temperature superconducting (HTS) maglev in recent years, several countries have built short-distance test lines for proving the feasibility of HTS maglev in the long-term running status, and the scientific exploration gradually develops from stable levitation experiments to dynamic performance tests. In previous studies, the sufficient levitation and guidance forces have been verified, but they ignore the influence of external disturbances in practical operations such as inhomogeneous magnetic fields along the permanent-magnet guideway, which limits the operation speed and causes potential vibrations. Meanwhile, the overlarge vibration might reduce the comfort of passengers and bring bad stability of the vehicle. Hence, the research of the dynamic characteristics in the actual operation process is an important process of the HTS maglev system. This paper makes use of the latest research result of a 45-m-long HTS maglev ring test line to study the dynamic vibration characteristics of the maglev vehicle under different running conditions, including different velocities, loads, and sections of the ring test line. Experimental results show that the amplitude of vibration acceleration increases with the velocity of the vehicle. In the vertical direction, the vibration acceleration curves reflect favorable axis symmetry, which confirms an excellent self-stable characteristic of the HTS maglev system, whereas in the lateral direction, the vibration acceleration has different trends on straight and curve lines. The lateral vibration acceleration on the straight lines is always fluctuating around the equilibrium position, and it has a rising trend on curve sections caused by stronger centrifugal phenomenon. Moreover, a proper increase in the levitation load can weaken the vibration, particularly with an enhancing velocity. These results help us to have a deep insight into the potential of HTS maglev and make preparations for the following long-distance dynamic tests.

Nonlinear vibration behaviors of high-Tc superconducting bulks in an applied permanent magnetic array field

The nonlinear vibration of high temperature superconducting (HTS) bulks in an applied permanent magnetic array (Halbach array) field, as a precondition for commercial application to HTS maglev train and HTS bearing, is systematically investigated. This article reports the actual vibration rules of HTS bulks from three aspects. First, we propose a new numerical model to simplify the calculation of levitation force. This model could provide precise simulations, especially the estimation of eigenfrequency. Second, an approximate analytic solution of the vibration of the HTS bulks is obtained by using the method of harmonic balance. Finally, to verify the results mentioned above, we measure the vertical vibration acceleration signals of an HTS maglev model, consisting of eight YBaCuO bulks, oscillating freely above a Halbach array with large displacement excitation. Higher order harmonic components, which indicate the nonlinear vibration phenomenon, are detected in the responses. All the three results are com...

Motion stability of the magnetic levitation and suspension with YBa2Cu3O7-x high-Tc superconducting bulks and NdFeB magnets

The flux pinning effect of YBa2Cu3O7-x high temperature superconducting (HTS) bulk can achieve self-stable levitation over a permanent magnet or magnet array. Devices based on this phenomenon have been widely developed. However, the self-stable flux pinning effect is not unconditional, under disturbances, for example. To disclose the roots of this amazing self-stable levitation phenomenon in theory, mathematical and mechanical calculations using Lyapunovs stability theorem and the Hurwitz criterion were performed under the conditions of magnetic levitation and suspension of HTS bulk near permanent magnets in Halbach array. It is found that the whole dynamical system, in the case of levitation, has only one equilibrium solution, and the singular point is a stable focus. In the general case of suspension, the system has two singular points: one is a stable focus, and the other is an unstable saddle. With the variation of suspension force, the two first-order singular points mentioned earlier will get close...

High-Temperature Superconducting Magnetic Levitation Vehicles: Dynamic Characteristics While Running on a Ring Test Line

In the long-distance operation of the high-temperature superconducting (HTS) magnetic levitation (maglev) systems, the dynamic characteristics of the vehicle are closely related to its security and stationarity, which require in-depth research to ensure its safe operation. Thus, we investigated the dynamic characteristics of the HTS maglev and assessed its safety and stationarity when running on a ring test line. In the experiments, the important parameters related to safety are lateral displacement (LD) and levitation height (LH). Results show that an appropriate low field-cooling height (FCH) is beneficial for its safe operation, and the maximum LD (MLD) should be considered in vehicle designs. Moreover, in other experiments, we tested the vibration acceleration of the HTS maglev vehicle using acceleration sensors and assessed its stationarity according to the Chinese National Standard GB5599-85, which is specifically published to assess the stationarity and security of railway vehicles by the China Ministry of Railways. The stationarity of the HTS maglev vehicle running on the ring test line is of good grade. When the secondary suspension and appropriate measures of vibration reduction are considered, the stationarity will be greatly improved.

Dynamic Vibration Characteristics of HTS Levitation Systems Operating on a Permanent Magnet Guideway Test Line

With the development of high temperature superconducting (HTS) maglev stepping in a key period of test line applications, the test and analysis of the dynamic operation parameters become more and more crucial. In this paper, the dynamic operating characteristics of single-cryostat and multicryostat levitation systems were comparatively studied on a 45-m-long permanent magnet guideway test line with different working conditions. Vibration acceleration signals of three levitation systems (a single cryostat, a bogie with two cryostats, and a car with four cryostats) were measured in the running experiments. The vibration characteristics were analyzed in both time domain and frequency domain. Results show that the multicryostat levitation system has better dynamic performance of stiffness than those of the single-cryostat system. The experimental data also indicates a positive correlation between the stability of the HTS maglev vehicle and the number of the cryostat. This work is helpful to understand the essential characteristics of HTS maglev vehicle system, and will be beneficial to the future design.

Effect of Eddy Current Damper on the Dynamic Vibration Characteristics of High-Temperature Superconducting Maglev System

The high-temperature superconducting (HTS) magnetic levitation (maglev) has demonstrated many advantages such as self-levitation, self-guidance, environment friendliness by using liquid nitrogen, and low noise. But it has a weakness of low damping, which is not beneficial for the systemic stability and security when the maglev vehicle is disturbed by external environment such as crosswind and track irregularity. To enhance the dynamic stability of the HTS maglev system, a simple and effective approach by inserting eddy current damper (ECD) into the bottom of HTS bulks has been considered. In this paper, we investigated the dynamic effect of ECD on the vibration amplitude and frequency of the HTS maglev system by introducing different thicknesses copper damper underneath the HTS bulks with different velocities by measuring the displacement and acceleration signals of an HTS levitator. In theory, we analyzed the effect of ECD on the dynamic stiffness. Experimental results manifest that the additional copper damper can effectively reduce the vibration amplitude of the HTS levitator, meanwhile it has little influence on the vibration frequency. The ECD has little effect on dynamic stiffness by theoretical analysis. An optimum thickness of copper damper to reduce the dynamic vibration is proposed for the HTS maglev system.