Study Of Electromagnetic Guideway For High Temperature Superconducting Maglev Transportation

Benefited from the “self-stable levitation” property of a bulk high temperature superconductor(HTS)in magnetic field,HTS maglev train is becoming one of the research focuses in maglev transportation these years.Up to today,many significant results in HTS maglev study have been obtained,dozens of testing lines have been built and tested all around the world.As the study of HTS maglev gradually turns into commercial application,new challenges appear.For the construction of long distance permanent magnetic guideway(PMG),a large number of high intensity permanent magnets are required,which consume huge amount of rare earth resources.Besides,the magnetic field of PMG is un-adjustable and degrades with time.The protection and maintenance of PMG is also demanding.All those problems may hold back the commercialization of HTS maglev transportation in the future.Electromagnetic guideway(EMG)is of some advantages,such as its magnetic field strength being adjustable and controllable,material cost and manufacture technology being favorable,and maintenance being much easier.In an attempt to overcome the disadvantages of PMG and to promote the commercial application of HTS maglev transportation,four primary topics of study were carried out in this Ph D dissertation.First,based on the principle of electromagnetic device design and the magnetic field requirements in HTS maglev,two EMG guideway prototype units,E-shaped and fan-shaped,were proposed.Feasibility analysis and comparative study were conducted on these units.Tests showed that the E-shaped unit had better levitation performance while the fan-shaped unit was more compatible with different arrangements of HTS bulks.Second,a quasi-static disturbance measurement method was proposed.In comparison with the popular static measurement method,the more degrees of freedom of the levitation part were realized and two position parameters were added to the guidance force measurement.As the result,the lateral disturbance could be measured and analyzed more accurately.Third,a number of excitation modes of the EMG unit were investigated with experiments and simulations.As compared with the commonly used displacement measurement method for PMG,the current variation measurement method proposed in this study was more helpful for practical force calculation and regulation.Based on the current variation idea,from measurement to operation,a novel levitation initializing method was further proposed.The new method could increase the simplicity of the initialization and the controllability of the levitation height.The special force distribution on the HTS bulk under the condition of reversed excitation was also investigated.It was found that the levitation and propulsion forces could be generated simultaneously on the HTS bulk in a reversed magnetic field,filling a gap in this kind of research.Last,the magnetic field homogeneity on straight and curved EMG models were analyzed and optimized.Then a novel EMG system operation mode was proposed.Through the cooperative work of forward excitation and reversed excitation,functions of suspension,guidance and propulsion were simultaneously realized without introducing any additional propulsion system.This operation mode may effectively reduce weight of train body and also may provide a novel idea for the future research of HTS maglev transportation.All the four topics of study are original and very innovative.The results of this study demonstrate the feasibility of replacing PMG with EMG in commercial applications of HTS maglev transportation.