Research On Novel Consequent-pole Permanent Magnet Linear Synchronous Machines

In recent years,with the rising price of rare earth materials,the ConsequentPole machine(CPM)has gradually become a research hotspot in the field of permanent magnet linear synchronous motor.Its advantages of less permanent magnet usage,low cost and high utilization of permanent magnet are very suitable for long stroke occasions.This paper comprehensively summarizes the domestic and oversea research status of consequent-pole machine and hybrid-excited motor.In addition,this paper compares the merits and demerits of various motor topologies and the problems existing in practical applications.Furthermore,on the basis of these academic and industry backgrounds,this paper demonstrates the engineering practical value of the new Consequent-pole hybrid-excited flux-reversal permanent magnet linear machine(CP-HEFRPMSLM)in the applicarions demanding long stroke,low cost and frequently variable speed.The topology,analytical model,working mechanism,electromagnetic performance,fault performance and prototype test are studied in details.The main work includes the following aspects:(1)The working principle of consequent-pole permanent magnet linear motor is deeply studied.According to the characteristics of consequent-pole structure,the magnetomotive force-airgap permeance model is established.The analytical expressions of permanent magnet produced electromotive force,airgap permeance function,winding function,open-circuit airgap flux density distribution,phase flux linkage,phase back-EMF and thrust force under three-phase symmetrical AC currents are deduced,and the contribution of different times of flux density field harmonics to thrust and thrust fluctuation is revealed.(2)A primary-pertitioned flux-reversal permanent magnet synchronous linear machine(CP-HEFRPMSLM)based on consequent-pole and hybrid-excited structure is proposed,which is suitable for low cost,long stroke and frequently variable speed applications.After analyzing the basic working principle and hybrid excitation mode,the machine topology is optimized and the electromagnetic performance is analyzed,including open-circuit airgap flux density,open-circuit back-EMF,thrust performance,detent force and inductance,etc.(3)The equivalent model of CP-HEFRPMSLM armature winding with inter-turn short-circuit fault is established.Combined with the resistance and inductance of the short-circuit ring,the changes of short-circuit ring current,phase currents with and without fault,winding copper loss and thrust performance after inter turn short-circuit fault are deeply analyzed.Furthermore,according to the longitudinal end effect of linear machines,the inter-turn short-circuit loop current,thrust performance and negative sequence component under different places of inter-turn short-circuit faults are analyzed and compared.(4)A CP-II HEFRPMSLM prototype is fabricated and a test platform is built.The open-circuit back-EMF and static thrust-current curve under different hybrid excitation conditions are tested to verify the correctness of theoretical analysis and finite-element method.