Research On Permanent-Magnet Eddy Current Loss Of Fault-Tolerant Flux-Switching Permanent-Magnet Machine

Fault-tolerant flux-switching permanent-magnet(FT-FSPM)machine has good application prospects in aerospace,war industry,wind power and other related fields due to their simple rotor structure,high torque density,and high efficiency.However,due to the rich harmonics of air-gap magnetic flux density in FSPM machine,its permanent-magnet(PM)eddy current loss is quite large,which leads to the high temperature of PM,causes PM irreversible demagnetization,lowers the electromagnetic performance of the machine.Therefore,considering the high reliability and low loss requirements,it is of great theoretical and practical value to investigate PM eddy current loss and its reduction method in FT-FSPM machine.Taking the 8/15-pole FT-FSPM machine as the research object,this paper analyzes the mechanism of its PM eddy current loss,proposes two methods to reduce the PM eddy current loss of FT-FSPM machine,and explains the principle of eddy current loss reduction.The research results of this paper mainly include the following aspects:1.Based on the magnetomotive force and permeability model of FT-FSPM machine,the no-load air-gap magnetic flux density,the load air-gap magnetic flux density and the rotational speeds of various harmonics are derived,respectively,which lay the theoretical foundation for the research of eddy current loss mechanism in FT-FSPM machine.2.Based on the skin depth of each harmonic in the FT-FSPM machine,the path of eddy current is investigated,which lays the foundation for the calculation of segmented PM eddy current loss.3.The effect of symmetrical PM segmentation on eddy current loss reduction is investigated under the condition that the skin effect is neglected.At the same time,the method of PM segmentation suitable for FT-FSPM machine is also given.4.Aiming at the difficulty of PM size reduction,manufacturing and assembly,two novel machines with magnetic flux barriers inserted in rotor are proposed to suppress sub-harmonic of the air-gap magnetic flux density,thus decreasing PM eddy current loss.5.A prototype of the original machine and novel machine with magnetic flux barriers are fabricated,respectively.The experimental platform is set up and the test analysis is performed.The measured results verify the validity of theoretical analysis.In addition,the PM temperature of these two machines is tested and compared,and it is verified that the proposed machine has a good effect on the PM eddy current loss reduction.