Study On Dynamic Characteristic And Its Improvement Method Of High Temperature Superconducting Maglev

Since the discovery of high temperature superconductors (HTS) which can realize a novel self-stable levitation in the external applied field without control, this material has been widely used in a variety of practical applications, such as superconducting bearing, flywheel energy storage system, transportation and so on. In 2000, the first man-loading HTS maglev test vehicle was successfully developed at Southwest Jiaotong University in China, which sets off a research boom in HTS Maglev. Based on the research work of HTS Maglev over ten years, the group further combines the HTS Maglev with the vacuum tube and completed the first evacuated tube HTS maglev vehicle test platform in 2014, which receives much attention in the world wide.Recently, the research about the HTS maglev mainly focuses on the electromagnetic property in the quasi-static state, including the levitation force, guidance force, stiffness and force relaxation. However, the HTS bulks inevitably experience the inhomogeneous magnetic flux density in the practical operation, which may have influence on the levitation performance of the HTS maglev. Therefore, in this paper we firstly tests the magnetic flux density inhomogeneity of the permanent magnetic guideway (PMG) which is a part of the high temperature superconducting maglev dynamic testing system, and investigates the magnetic field fluctuations of the PMG in the dynamic running at the same time. It is found that the magnetic flux density of the PMG along its operational direction is inhomogeneous and the iron can relieve the inhomogeneous of the magnetic flux density.Afterwards, the levitation performance and the magnetic field of the HTS bulks were investigated in the quasi-static state. We focus on the levitation force and magnetic field changes of different locations at upper and bottom surface of the bulks in conditions of different field-cooling heights and working heights, and expound the underlying cause of the levitation force variation from the perspective of the magnetic field above the bulks surface. It is found that the levitation force of HTS bulk is closely related to the surface magnetic field of the HTS bulk. Subsequently, the levitation performance and the magnetic field of the HTS bulks were studied in the dynamic running condition (including different running speed, field-cooling height, working height and circulatory acceleration and deceleration), and the influence of the magnetic fluctuation on the levitation performance of the HTS maglev was analyzed.Finally, specific to the dynamic operation characteristics of the HTS Maglev, this paper proposes and investigates two improvement methods. One is that adding the copper plate at the bottom of the bulks as an eddy current damper to study its influence on the dynamic levitation force and vibration characteristics. Experimental results show that the eddy current damper can improve the levitation performance of HTS maglev system, relieve the decay of dynamic levitation force. Besides,0.5 mm thickness of eddy current damper is more beneficial for the dynamic vibration characteristics than others. The other one is introducing the spring into the HTS Maglev as the mitigation measure to investigate its improvement effect on the vibration characteristics of the part above the levitation model. It is found that the vibration acceleration on the upper of the levitation model with spring is much less and the spring can shield the external excitation at high frequencies over 30 Hz.