Design And Analysis Of A Flux Intensifying Permanent Magnet Brushless Motor

With the rapid development of economy,the automobile industry is also booming.However,when the development of the automobile industry gives people travel convenience,it also exacerbates the energy crisis and environmental pollution problems.In order to alleviate the energy crisis and reduce environmental pollution,electric vehicles(EVs)possessing advantages of energy saving and environmental protection has become a new direction of the development of the automotive industry.With the strengthening of people's awareness of environmental protection,EV has developed rapidly and becomes an alternative for people to travel by means of transportation.The excellent performance of the driving motor is the key to ensure the superior performance of EVs,thus the driving motor of EVs has aroused wide research.Due to the advantages of high power density,high torque density and good dynamic performance,the traditional interior permanent magnet brushless(IPMBL)motor is widely applied in EVs.But because of the nonadjustable PM magnetic field,the traditional IPMBL motor is difficult to possess a wide constant-power speed range and high efficiency,which makes it cannot meet the requirements driving motor applied EVs.To solve above problems,a new flux intensifying permanent magnet brushless(FI-PMBL)motor has attracted research interest of scholar,which has a extended speed range.The proposed new motor not only inherits the advantages of traditional IPMBL motor,but also has large d-axis inductance to extend the constant-power speed range.Meanwhile,the risk of irreversible demagnetization of PMs can be reduced,benefiting from the flux-intensifying effect.In this paper,the development background and current situation of EVs,and the merits and demerits of motor driving system are introduced firstly.The existing methods and problems to achieve the wide speed range of motor are also discussed.According to the existing research,by borrowing the concept of flux-intensifying effect,two kinds of FI-PMBL motor owing superior wide speed range performance are proposed structure have been proposed.The two motors adopt non-uniform air gap flux barriers(FBs)and interior multilayer flux barriers respectively.Secondly,the optimal design procedure of the motor this is expound,and working principle is analyzed.Meanwhile,rated parameters and main dimensions are determined and calculated.Then,the optimal design of the stator and rotor structure of two kinds of FI-PMBL motors are carried out.Through theoretical analysis,the winding connection type is determined,and the size of PMs and FBs are optimized to further enhance the flux-intensifying effect.In the end,the structure parameters of the two proposed FI-PMBL motors are determined.Then,the basic electromagnetic performances of the two FI-PMBL motors are analyzed and compared by using the finite element simulation software,including air-gap flux density,no-load back EMF and inductance characteristics and so on,and the traditional IPMBL motor is used as the reference object.In addition,the mechanical strength of two new motors is analyzed by structural stress analysis software,including stress analysis and deformation analysis.Then,based on the traditional IPMBL motor,the control strategy and the vector trajectory of the new motor under wide speed range operation are analyzed.Through theoretical analysis and finite element simulation software,the performance of two FI-PMBL motors under wide speed rang operation are analyzed and compared.And,the proposed motors are proved to have superior wide speed range performance.Finally,the prototype of FI-PMBL motor is manufactured,and back EMF,inductance and torque characteristics are tested by building the experimental platform.The experimental results and simulation results are basically same,which verifies the rationality and correctness of the design of FI-PMBL motor.