Analytical Modeling And Optimization Of Brushless Permanent Magnet Machines With Novel Magnets

With the improvement of the production process of permanent magnet(PM)machines and the continuous emergence of new permanent magnet materials,PM machine systems tend to be more compact,high efficiency,low noise and high reliability,and their application prospects are more extensive.The novel structure and electromagnetic performance of PM machines are investigated.Therefore,it has theoretical significance and engineering value.The cogging torque exists in the PM machines with slotted stator.Considering different assumed conditions,the cogging torque is analytically obtained and compared by the energy method and the Maxwell stress tensor method.The prediction results show that the predictions are more accurate accounting for more actual conditions.The shape of the magnet has a great influence on the magnetic field distribution in the PM machine.In this paper,two PM machines with salient semicircular/trapezoid are proposed.First,two kinds of permanent magnets with salient shape unequal thickness magnet are modeled by superposition.Second,then the air gap flux density is analytically obtained by an accurate subdomain model method,and other electromagnetic performances are analytically obtained.Third,the influence of the structure parameters of two salient shape on the electromagnetic performance of PM machine with unequal thickness magnetic poles is analyzed.Finally,the correctness of the analytical model is verified by a finite element method.An analytical model of a surface-inserted PM machine with novel magnetic poles is proposed.Each magnetic pole is composed of two equal symmetric segments.The influence of the magnetization direction of each segment on the electromagnetic performance of the PM machine is investigated.In addition,for the maximum fundamental air gap flux density,the optimal magnetization angle is obtained by the optimization method.The prediction results show that the PM machine with novel magnetic poles has better electromagnetic performance compared with conventional parallel magnetization PM machine.The results by the analytical method and the finite element method are compared,which proves the correctness of the analytical model.