Research On Magnetic Network Modeling And Vibration Characteristics Of Modular Interior Permanent Magnet Machines

Recently,the development of electric space systems has attracted great attention from researchers.As a key component of electric drive systems,the reliability of machines is very important for aerospace equipments.In order to improve the ability of machines to deal with faults,a four-modules permanent magnet synchronous machine(PMSM)is designed by combining the modular topology with PMSM.This paper focuses on the modular machines design,equivalent magnetic network(EMN)modeling and vibration characteristics prediction,and mainly carries out the following work.Firstly,according to the characteristics of the modular topology,the pole-slot combinations and different winding forms of machines are studied,and the scheme suitable for stator modularization is given.By comparing the electromagnetic performance of five kinds of PMSMs,the v-type interior rotor is selected.The skewed stator is used to reduce the torque ripple and back-EMF harmonics,and the improvement on the electromagnetic performance is verified by finite element analysis(FEA).Secondly,this paper develops an improved equivalent magnetic network(IEMN)model for analysis of a modular interior permanent magnet(IPM)machine.Focusing on the local magnetic saturation,the stator tooth crown is divided into three parts based on its structure and flux density distribution.To model the specific flux path,the tooth tips on both sides are approximated to right-angled trapezoids and the middle part is divided into isosceles trapezoid.An improved air-gap model is proposed,which divides the air-gap magnetic network into three layers.The middle network uses cross-shaped mesh(CS-M)elements to represent the path of tangential and radial flux.The top and bottom layers are composed of parametrized nonlinear permeances between stator,rotor edge nodes and middle network nodes,whose values are the function of angle respect to CS-M elements.In this way,as machine rotates,the structure of the IEMN model can be kept invariant,and only permeances of bottom layers should be modified.Then,the IEMN model is extended to the analysis of the machine with skewed stator.The accuracy and effectiveness of the proposed IEMN model are verified through comparisons with FEA and experimental tests.Finally,based on the IEMN model and FEA simulation,the vibration characteristics of modular machines is investigated.The temporal and spatial harmonic of radial electromagnetic force and torque characteristics are calculated by IEMN,and the vibration level of machines is predicted qualitatively.In order to quantitatively analyze the vibration performance of modular machines,accurate 3D models of straight and skewed stators are constructed,and the modal parameters of stator systems are calculated by FEA.The vibration acceleration on the housing surface is computed by FEA with loading different electromagnetic excitations on the stator inner face.The influences of different operating conditions and the skewed stator on the vibration performance are studied.And the vibration characteristics under the radial magnetic force and electromagnetic torque are analyzed and compared.