Research On Characteristic Of Long Ironless Stator Double-sided Doubly-fed Linear Motor

We put forward higher requirements for the economic and high-speed performance of maglev technology as the medium-low maglev is becoming mature.The Long Stator Linear Motor(LSM),which needs to lay ferromagnetic materials such as silicon steel sheet for a long distance,is used to provide traction power for high-speed maglev.Thus,the high-speed maglev project cost is too high to have more advantages than high-speed rail transportation.And this paper proposed a new linear motor----Long Ironless Stator Double-Sided Doubly-Fed Linear Motor(hereinafter,LIS-DSDFLM).And the characteristics of LIS-DSDFLM is studied by combining mathematical model and finite element simulation.Furthermore,we explore its application in high-speed maglev train,and concludes that LIS-DSDFLM has more economic advantages than LSM.Firstly,the paper introduces the basic structure and working principle of LIS-DSDFLM.The mathematical models of LIS-DSDFLM in abc three-phase static coordinate system and dq two-phase rotating coordinate system are established according to the theory of linear motor.Besides,the expressions of the impedance are derived and one-dimensional air-gap mathematical model are established according to the concept of equivalent current sheets,which gives the expression of thrust force.Secondly,the structure parameters of LIS-DSDFLM meeting the requirements of medium-low speed maglev are obtained by using Maxwell script modeling and simulation iteration.LIS-DSDFLM has the advantages of slightly larger thrust,lower normal force and higher efficiency than SLIM with the same electric load of the mover,;The finite element models of LIS-DSDFLM and Doubly-Fed Linear Motor(hereinafter,DFLM)are established with the same structural parameters.The simulation results show that LIS-DSDFLM can provide the same traction force,but the normal force and stator inductive voltage of LISDSDFLM is far less than that of DFLM.Another simulation experiment shows that the change of air-gap has little effect on the traction and normal force of LIS-DSDFLM.The accuracy of the above theoretical analysis is verified by comparing the electromagnetic thrust and air gap magnetic field of the simulation results with the analytical calculation results.And it is pointed out that the accuracy of thrust calculation by air gap magnetic field angle is higher than that by circuit equation.Then,we studied the influence of stator winding structure on LIS-DSDFLM considering that the stator winding has no core magnetic effect.Two single-layer ironless winding structures are established,and the current density harmonics are analyzed according to the structure characteristics.The optimal structure parameters of the two single-layer air core windings are set through simulation experiments,and compared with the above-mentioned double-layer stacked wound LIS-DSDFLM from two aspects of motor performance and efficiency,it is concluded that the single-layer stacked LIS-DSDFLM has more advantages.Finally,LIS-DSDFLM is applied to high-speed maglev train.Referring to the characteristics of Shanghai TR08 high-speed maglev train,the resistance model of high-speed maglev train is established,and the structural parameters of single-layer stacked LISDSDFLM are adjusted to meet the operation requirements.Combined with the adjusted structural parameters of LIS-DSDFLM,the characteristics between stator current,train speed and traction force are studied.It is found that LIS-DSDFLM has higher maximum theoretical running speed than ordinary LSM under the same restrictive conditions(stator section length,stator end voltage and stator current).Therefore,LIS-DSDFLM has certain advantages over LSM in high-speed maglev applications.