| As widely used motion source,permanent magnet synchronous motors have many advantages such as high power density,low loss and fast dynamic response.The servo systems which have the core component of the permanent magnet synchronous motor solve many technological problems for manufacturing and related industries.The permanent magnet synchronous motors have many rotor structures.As a product of its optimum design,polygonal rotor magnetic yoke has many advantages in improving sine degree of back EMF and reducing torque ripple,which attracts more and more attention.However,the research about rotor force condition of this structure is not enough,which restricts the further improving of its performance.Therefore,taking polygonal rotor magnetic yoke permanent magnet synchronous motor as research object,this paper carried out 2-d electromagnetic force characteristics research basing on the analytical method of dividing magnetic field into parts,which has considerable significance for this structure's further application and development in permanent magnet synchronous motors.In this paper,the research work was divided into four stages.Due to the magnetic field is the basis of electromagnetic force solving,this paper finished analytical calculation of no load air-gap magnetic field using the method of dividing the region into parts at first.In the solving process,the whole field was divided into 4 parts,and the interface conditions were used to connect them.Due to the particularity of polygonal rotor magnetic yoke structure,radius function of rotor magnetic yoke and the radius function of eccentric permanent magnet were put forward to describe the uneven air gap length.According to the matrix equation transformed from the interface conditions,the distribution of air-gap magnetic field was determined.The calculation results of this method can catch the results of finite element analysis highly.Secondly,ignore the magnetization of permanent magnets and assume permanent magnet and air gap having the same relative permeability.So the motor surface domain can be divided into 3 parts.The air gap magnetic field of armature reaction was calculated in the similar method and the calculation results were compared with finite element analysis,which have high matching.So the analytical calculation process can be verified to be correct,which establishes the basis of load air-gap magnetic field and 2-d electromagnetic force analysis.Thirdly,based on the calculation results of air gap magnetic field analysis of first two chapters,2-d electromagnetic stress distribution of polygonal rotor magnetic yoke permanent magnet synchronous motor was solved according to maxwell stress formula.The results were decomposed into 3 parts and each part was analyzed detailedly.The 2-d electromagnetic stress difference between polygonal rotor magnetic yoke and circular rotor magnetic yoke was explored.Also,2-d electromagnetic stress of radial component and tangent component were transformed into X and Y direction components and the whole unbalanced magnetic pull of rotor is obtained by integral calculation.And then,the characteristics of unbalanced magnetic pull and the relationships between unbalanced magnetic pull and motor structure size were explored.Finally,the experimental prototype structure was designed and 4 experiments were conducted.The back EMF and inductance tests verified the validity of the magnetic field analysis.The unbalanced magnetic pull tests verified the validity of the analysis of 2-d electromagnetic force. |
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