Experimental Investigation On The Electromagnetic Forces Of Non-insulated HTS Coils On A Coreless Stator

High speed maglev trains,which take advantage of the electromagnetic forces to drive the vehicle and get its traction power from the grounded linear motor,have become an inevitable choice for higher speed rail transportation because it could avoid the speed limitation from the adhesion of wheels and rail and the function of the power supply system as pantograph and catenary.Due to the excellent current-carrying property,lower losses and ideal electromagnetic performances,the high temperature superconducting(HTS)magnet could be used to boost the thrust density and power factor of linear motors and guarantee its good thrust output capacity even with large air gaps and become an ideal choice for high speed maglev system.The performance of both HTS coils and the stator of the linear motor plays a crucial role in the operation of linear motors and it is vital for the investigation on the HTS linear driving system.This paper takes the electromagnetic forces of the non-insulated high temperature superconducting magnet working on the coreless stators as the research object and introduces the combination of finite element simulation and experimental methods.The investigations on design of both primary structure and the parameter of HTS magnet,the winding method for the HTS coils,the modelling of HTS linear motors,the manufacture of the experimental prototype and the electromagnetic property comparison of a counterpart with an iron core structure were carried out in this work.First of all,the performance characteristics and application advantages of centralized and distributed winding methods were compared during the design for the armature windings.The double layer distributed winding method was chosen for it would produce less of higher harmonic component and better sinusoidal performance in applications.The electrical parameters as the circuit configuration and the connection mode were designed for the stator.Based on the machinability and the self-field electromagnetic performance of the coated HTS tapes,the design and analysis of the non-insulated HTS coils were finished.Besides of this,a two-dimension finite element model was established to calculate the electromagnetic forces which takes the nonlinear E-J power law into consideration in simulation.Secondly,the prototypes for both type of stator were manufactured according to the parameters and characteristics of the coreless and iron core armature windings.In addition,two non-insulated HTS coils,which are potentially used for linear motors,were wound according to the comparison result of the winding methods and technical features for insulated and non-insulated coils.The epoxy frames and fixture of the coils were designed and manufactured.Finally,an experimental system that could be used for HTS linear motor testing was constructed.The investigation of how the ac current in the armature windings would influence the thrust forces of the linear motor was carried out and it was found that the coreless HTS linear motor could output acceptable thrust with a large airgap.The experimental results of the normal forces for both prototypes proved that the coreless linear motor had the advantages as less attraction forces,less fluctuations in electromagnetic forces and better stabilities.The experimental and calculation results has proved the feasibility of the coreless HTS linear motor in the high speed maglev systems.