Research On The Force Charecteristics Of High Superconductor Magnet Under Linear 3-phases Windings

Experimental and theoretical achievements have been made in high temperature superconducting (HTS) linear motors starting since the end of last century. In particular, most experiments made use of YBCO bulk samples with trapped flux as magnets or Bi-2223 composite multi-filamentary wire as electromagnets as a mover or stator of the HTS linear motor. However, coils wounded by the second generation superconducting wire YBCO coated conductor tape have never been used for which its in-field performance is much better than the Bi-2223 wire, especially at the liquid nitrogen temperature. This dissertation mainly focused on the static thrust of superconducting components as the excitation system of a linear motor and their respective magnetic field distributions. Apart from the experimental measurement of thrust generated by the superconducting excitation system in a single-sided flat linear synchronous motor system, the normal forces were also monitored which is an important parameter for stable operation. The obtained experimental results were compared to theory through computational analysis with Comsol. The first man-loading HTS maglev was successfully developed at our laboratory, the Applied Superconductivity Laboratory of Southwest Jiaotong University, in December of 2000. The levitation gap between the maglev and the permanent magnet guideway (PMG) was over 20 mm. A linear induction motor was chosen to provide the driving force for the reason that its influence to the levitation system would be small. However, the efficiency and power coefficient are low due to the large gap between the primary and secondary. An HTS linear motor with a large energy density and high power output could be introduced into the HTS maglev system for driving. Furthermore, the levitation, guidance and driving systems can be integrated so that energy loss can be further reduced and efficiency of the system increased. The purpose of this work was to survey more advanced driving systems for the HTS maglev, the plan of using second generation HTS coated conductor tape as the excitation unit for the linear motor is first introduced. This research emphasizes on flat single-sided HTS linear synchronous motors for driving systems in maglevs.In the first studied case, using an HTS YBCO bulk which can trap magnetic flux after undergoing a magnetization process which then acts as a "quasi-permanent magnet", and therefore as a magnetic field source, the magnetic forces experienced by this bulk piece under a sinusoidal magnetic field generated by the primary winding of the linear motor system was studied experimentally. The magnetic trapped flux inside the HTS bulk, the magnetic flux density above the primary windings, and the influence of various paramaters of the linear motor on the force and the decay of amplitude are discussed.In a second case, three separate coils with different structures all made of YBCO coated conductor tape were studied:circular shaped single-pancake, circular shaped double-pancake and a racetrack shaped single-pancake coil. The thrust and normal forces of said three coils above a conventional copper wire wound armature were studied experimentally. The effects of the exciting current feed to the superconducting coils and the parameters of the AC power input to the primary on the thrust and normal forces are discussed. The racetrack shaped single-pancake coil was studied more thoroughly since it is the most suitable for flat single sided primary winding systems. This racetrack shaped single-pancake coil was further investigated by studying its effect of the number of turns, frequency, containing an iron core and iron back plate on the forces between the excitation system and the armature.Lastly, the finite element method software was used to simulate the HTS linear synchronous motor. The details of the two-dimensional HTS linear motor model and the calculation processes are introduced. By comparing the simulation results with the experimental ones, the validity of the simulation model was verified. Furthermore, the influences of the coil height and number of turns on the forces were investigated by the simulation method. Optimization of the coil was also performed upon introduction of ferromagnetic material to the coil in the form of iron cores and yokes of different sizes.The work in this manuscript will greatly help the further development of medium and large-scale HTS linear synchronous motors. By the scaling up of the systems studied, the HTS linear synchronous motor will be the most practical form of drive to propel the existing HTS Maglev test vehicle system and other conventional maglev systems.