Research On Rotor Loss Characteristic And Suppression Of Permanent Magnet Vernier Machine

PMV machine has attracted extensive research interest due to its simple structure,high torque density and other advantages.However,compared with the traditional permanent magnet machine,PMV machine will produce a large loss during operation,which will lead to its low efficiency,so it is difficult to meet the needs of high efficiency electric drive fields such as ship power,aerospace,electric vehicle,etc.Therefore,it is very important to analyze and restrain the loss of PMV machine.However,the research on the loss of PMV machine is very scarce at present,which limits its further development in the field of high reliability.In this paper,through establishing the air-gap magnetomotive force and permeability model of PMV machine,the permanent magnetic field and armature reaction magnetic field are analyzed.On this basis,the loss and torque generation mechanism of PMV machine are analyzed,and an effective method to suppress the rotor loss of PMV machine is proposed,which is verified by analytical method and finite element analysis method.Finally,two prototypes were manufactured and an experimental test platform was built to verify the effectiveness and correctness of the loss suppression method of PMV machine.The research results can be summarized as follow aspects:1.The working principle of PMV machine is analyzed in detail from the perspective of magnetic field modulation effect,which lays a foundation for analyzing the air-gap magnetic field of PMV machine.2.Through the establishment of the air-gap magnetomotive force and permeability model,the analytical expressions of no-load air-gap flux density and armature reaction air-gap flux density of PMV machine are derived.According to the analytical expressions,the harmonic spectrum and frequency characteristics of each harmonic in the air-gap magnetic field are obtained,and the working harmonics and non-working harmonics in the air-gap magnetic field are distinguished.Then,the correctness of the analytical expressions of air-gap flux density is verified by finite element simulation.3.Based on the analysis results of air-gap magnetic field,the rotor loss and torque generation mechanism of PMV machine was studied.Meanwhile,the harmonics of air-gap magnetic field were connected with the internal harmonics of permanent magnet and core.The contribution of each harmonic in the magnetic field to the loss and torque of PMV machine was analyzed by analytical method,and the analysis results were verified by finite element simulation.4.According to the rotor loss and torque generation mechanism,a method to reduce the loss of PMV machine is proposed,which can reduce the loss by suppressing some non-working harmonics without sacrificing the torque density of PMV machine.The specific method is to introduce flux barriers into the yoke of the rotor and change the air-gap permeability of the rotor,so as to achieve the effect of suppressing the unwanted harmonics in the air-gap harmonic spectrum.The analytical method and finite element simulation are used to verify the effect,and the results show that the method is effective and correct.5.According to the results of loss suppression research,the PMV machine was optimized and a new type of machine structure with low rotor loss was proposed.The performance of the newly designed PMV machine and the original PMV machine,including no-load back-EMF,electromagnetic torque,rotor loss,permanent magnet demagnetization ability,was compared and analyzed by Maxwell simulation software.The results show that the rotor loss suppression effect of the newly designed PMV machine is obvious under the condition that the torque density is basically unchanged.6.Two prototypes were manufactured and an experimental test platform was built.The no-load test and load test were carried out on the two prototypes,and the electromagnetic properties such as no-load back-EMF,electromagnetic torque,machine loss and efficiency were tested.The experimental results show that the torque performance of the newly designed PMV machine is basically the same as that of the original one,but it has lower loss and higher efficiency,which is consistent with the theoretical and finite element analysis results.The effectiveness and correctness of the proposed loss suppression mechanism analysis and suppression method are verified.