| As a member of stator-permanent magnet(PM)machine family,the flux-reversal(FR)PM(FRPM)machine has a rather simple rotor structure without any PMs or field windings since it usually houses the PMs in the stator side rather than rotor side.Besides,it is usually equipped with concentrated armature windings.Thus,it shows a good potential in some special applications.After more than 20 years' development,fruitful achievements have been made,including the working principle,topology exploration,stator-slot/rotor-pole-pairs(slot/pole)combination,mathematical modeling and control methods.However,there are still some gaps to be filled,such as analytical solutions to magnetomotive force(MMF)excited by PMs and armature reaction field respectively,mathematical modeling of winding inductances,cogging torque and its corresponding reduction techniques,unbalanced magnetic pull(UMP)and its corresponding reduction techniques,machine design procedure and optimization methods,etc.Aiming at the shortcomings above,a comprehensive research on FRPM machines are conducted.The key contributions and contents of this dissertation are as follows:1.Based on coil-EMF vectors,winding connection pricinple of FRPM machines is investigated.The compensation effect of back-EMF in FRPM machines is unveiled.Besides,the modeling of winding factor which comprises of pitch factor and distribution factor is studied.Based on MMF-permeance model,the operation principle of FRPM machines is explained from the viewpoint of air-gap field modulation theory.Besides,an analytical model of back-EMF is also derived,according to which the corresponding optimization methods are proposed.2.Based on the mathematical modeling of MMF,the influences of some key parameters,such as magnetization methods,winding layer,coil pitch and rotor pole pairs,on MMF are investigated.Meanwhile,the harmonic characteristics of MMF are analyzed.Then,the effects of MMF harmonics,winding structure and phase current on power loss are investigated.3.The winding inductance of FRPM machines is modeled,including air-gap compenent,slot-leakage component and end-leakage component.The effect of rotor pole number on inductance is studied.Further,the reason why FRPM machines don't have saliency effect is unveiled.Then,the topology that can reduce the mutual-inductance in fault-tolerant FRPM machines is investigated.4.The cogging torque and unbalanced magnetic pull(UMP)of FRPM machines are modeled by both superposition method and MMF-permeance method.Then,the corresponding reduction techniques based on asymmetric permeance is proposed,including asymmetric rotor slot/tooth width.The corresponding cogging torque reduction techniques based on asymmetric MMF,asymmetric permeance,shifting rotor teeth,shifting stator teeth and multidimensional methods are proposed,which can be also extended to some other stator-PM machines.Besides,the effects of key parameters on UMP are discussed,including slot/pole combination,winding layer,magnetization methods and phase current.The corresponding reduction method is also proposed.5.A general power equation of FRPM machines is derived.The principle of choosing slot/pole combination is analyzed by taking the back-EMF,cogging torque,torque properties and fault-tolerant ability into consideration.The key dimensions in both stator and rotor sides are also optimally chosen,including magnetization method,PM arrangement,stator/rotor yoke dimension,stator/rotor tooth width,PM width,air-gap length and rotor tooth shape.Thus,a general design method can be obtained.6.The differences between FRPM machines and conventional rotor surface-mounted PM machines are compared.The 6/8,12/10,12/11 and 12/14 prototyped FRPM machines are manufactured(both magnetization methods considered).The testing platform are built and the key electromagetnic charactertistics,including back-EMF,winding inductance,cogging torque and overload/flux-weakening capability are measured,which successfully verifies the theoretical and simulated analyses. |
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