Space Harmonic Analysis And Low Harmonic Design Of Permanent-magnet Fault-tolerant Machine

Permanent-magnet(PM)machines are widely applied due to the advantage of high reliability.Higher fault-tolerant ability is further required in safety-critical applications,for example,electric vehicles and aerospace.Fractional-slot concentrated-windings(FSCW)configuration is very suitable for permanent-magnet fault-tolerant(PMFT)machines due to the low coupling between phases.However,abundant stator magnet-motive force(MMF)harmonics limits theirs application in the fault-tolerant machines,which will not only increase rotor eddy-current losses,therefore higher temperature and lower efficiency,but also lead to vibration and noise.Thus,it is of great significance to develop the low harmonic design of PMFT machines with FSCW configuration.In this thesis,the research on the space harmonic analysis of PMFT machines and their low harmonic design will be carried out.Firstly,in order to guide the low harmonic design of the PMFT machines,the general analysis method of MMF harmonics is presented by using AC winding theory.Then,three low harmonic design technologies,including star-delta hybrid connenction windings,rotor flux barrier and stator modulation,are investigated.Finally,the fast calculation methods of the efficiency nephogram and the quantitative analysis method of the maximum efficiency point and the specific efficiency area,are proposed.Experimental results on these PMFT machines are given to verify the theoretical analysis.This work lays a foundation for further application and efficient operation of PMFT machines,such as aerospace,military equipment,mine and rolling.The fruits of this thesis are as follows:1.The characteristics of the winding configuration of PMFT machines are analyzed.The concept of slot-pole combination normalized ordinal number pair is introduced,and on this basis,the general calculation method of the phase winding MMF of PMFT machines is derived.Besides,the distribution law of phase winding MMF harmonics is revealed.2.The structure characteristics and phase shift laws of multiple sets of symmetrical positive m-phase windings are studied.From the three aspects of one set,even-set,and odd-set of symmetrical positive m-phase windings,the calculation method of PMFT machines synthetic MMF is systematically derived.Moreover,the inherent relationship between the synthetic MMF harmonics and the winding phase shift is clarified.3.The low-harmonic design technology of double-layer prime phase PMFT machine with star-delta hybrid connection(SDHC)windings is studied and the essential characteristics of the SDHC winding structure are analyzed.The principle of adaptation between the phase number and slot-pole combination of this type PMFT machines is investigated.The specific law of MMF harmonic elimination in SDHC winding configuration is deduced.4.The low-harmonic design technology of rotor flux barrier of single-layer surface-mounted PMFT machine is studied.Based on the characteristics of the harmonic magnetic circuit of the armature reaction magnetic field,an equivalent permeance model of the rotor flux barrier structure is established.The armature reaction flux density expression of this type of low-harmonic PMFT machines is derived.Also,the quantitative relationship between the rotor flux barriers and the armature reaction flux density harmonics is revealed.5.The stator modulation low-harmonic design technology of the vernier PMFT machine is studied.Based on the vernier PMFT machine which satisfies the specific modulation law,the magnetic field harmonic variation principle of the PMFT machine under the modulation effect is investigated.Besides,the intrinsic relationship between the MMF harmonics and modulation harmonics of the vernier PMFT machines is derived.6.The equivalent point current finite element calculation model is developed and it effectively separates the armature reaction magnetic field harmonics in the complex coupled magnetic field and provides a simulation basis for quantitatively evaluating the influence of space harmonics on FTPM machines.7.The quantitative expressions of PM machine losses under different working conditions are established and its efficiency function is reconstructed.A fast and highly portable method for calculating the efficiency map of PM machines is proposed.The internal relationship between the maximum efficiency point of the PM machine and its specific high-efficiency region and loss distribution is studied quantitatively...