Research On Key Issues Of Flux-switching Machines

The flux-switching machine(FSM)is a typical structure of stator excitation brushless machines,which has field excitation sources(permanent magnets(PMs)or/and wound field windings)and armature windings on stator,and no PMs nor windings on rotor.The FSM has a bright future in the applications of electric vehicles,more-/all-electric-aircrafts,aero generators,and wind power generators and so on,due to its inherent advantages,such as superior torque density,high efficiency,excellent fault-tolerance,strong irreversible demagnetization withstand capability,favorable high-speed operation,and good thermal dissipation and liquid cooling conditions,which has attracted extensive attention of domestic and foreign scholars.After nearly 20 years of development,fruitful results have been achieved in terms of operation mechanism,topology design,and control strategy of the FSMs.However,there are still some deficiencies in the research of some key issues,including:(1)General design principle of stator poles and rotor teeth combinations of FSMs;(2)Elaborate analysis and utilization of reluctance torque of FSMs;(3)Influence of armature reaction on excitation field and accurate mathematical model of wound-field FSMs.In this dissertation,the three key issues mentioned above are studied in depth,and the innovations and contents of this dissertation can be summaraized as follows:1.The FSMs can be briefly classified into traditional type and derivative type.According to the number of armature winding phases,the traditional FSMs can be further divided into prime-phase structures and composite-phase structures.Firstly,the mathematical model for the stator poles and rotor teeth combinations of the prime-phase traditional FSMs is established and the general relationship between stator poles and rotor teeth is summarized.Then,based on the results of the prime-phase structures,the stator poles and rotor teeth combinations of the composite-phase structures are deduced.Thus,the relationship between the stator poles and rotor teeth of the traditional FSMs covering all phase numbers is determined.2.In the perspective of stator poles and rotor teeth combinations,the process of derivating new FSMs from the traditional FSMs is sorted out.Then,the stator poles and rotor teeth combination principles of the derivative structures are deduced based on the results of the traditional FSMs,which avoids blindness and contingency in the innovation process of derivative FSM structures.3.For a 6-armature-slots/5-rotor-teeth(6/5)wound-field FSM,the power-sizing equation is derived,and then the key geometries of the 6/5 FSM are obtained through the equation.Thereafter,the coupling relationship between the wound field and armature reaction field is disclosed.Based on the the frozen permeability method,the electromagnetic characteristics of FSM are analyzed in details,including the wound-field winding and armature winding inductances.Afterwards,an accurate mathematical model of the wound-field FSM is established on both stationary and rotary reference frames.4.In order to improve the fault-tolerant operation ability of the wound-field FSM,the characteristics under the condition of field excitation fault are studied.As the field excitation fault occurs,the wound-field FSM would be switched into a switched reluctance machine and operated under switched-reluctance mode,namely fault-tolerant operation mode,where the reluctance torque(1/3~1/2 of the rated torque) is utilized to keep the stable operation of the FSM.5.A 6/5 4k W wound-field FSM is manufactured,and the experimental platform is set up to fully test the prototype.The experimental results verify the mathematical model and the results from finite element method(FEM)efficiently.