Research On Starting Process For Demagnetization Of Line Start Ferrite Permanent Magnet Assisted Synchronous Reluctance Motor

Compared with line start NdFeB permanent magnet motor,the line start ferrite permanent magnet assisted synchronous reluctance motor has higher cost performance.However,due to the low coercive of ferrite and the large stator current during the starting process,the ferrite is facing the risk of demagnetization.At present,the literature on demagnetization of the line start ferrite permanent magnet assisted synchronous reluctance motor is limited.Therefore,the research on starting process for demagnetization of line start ferrite permanent magnet assisted synchronous reluctance motor has high theoretical and practical significance.In chapter 1,the relevant research results and research status of permanent magnet demagnetization are introduced.In chapter 2,the demagnetization characteristics of different permanent magnet materials are compared,and the significance of demagnetization research in starting process of the motor is clarified.The mechanism of irreversible demagnetization of ferrite during starting process is analyzed and studied by finite element method.The the change regulation of flux density at special points of ferrite and its average working flux density can be obtained by simulation calculation,and the differences between the two kinds of flux density change regulation are compared.The demagnetization trend of permanent magnet can be judged by the change regulation of flux density.The specific demagnetization area of ferrite during starting process is obtained by using the transient finite element method.The changes of starting ability and torque ability of the motor are compared.In chapter 3,the influence of different rotor structures on the demagnetization of the motor is studied,including the different rotor bars arrangement,rotor slots and magnet arrangement.The change regulation of flux density,irreversible demagnetization rate and specific demagnetization area of permanent magnet are solved.The demagnetization of different rotor structure motors is analyzed,and the anti-demagnetization ability of motor is compared when different grades of ferrite are applied to the same rotor structure.In chapter 4,the influence of initial position angle of rotor,initial phase angle of voltage,overload condition,short circuit,phase absence,rotor bar breakage and load change on demagnetization of permanent magnet of the motor is studied by building external circuit model and combining with transient finite element method.The change regulation of ferrite flux density is studied,the demagnetization trend of ferrite is analyzed,and the demagnetization area of the motor is solved.In chapter 5,the demagnetization simulation experiment and field experiment of a 1.5kW Ferrite Line Start Permanent Magnet Assisted Synchronous Reluctance Motor have been carried out in the laboratory.The reliability of the analysis method is verified by the prototype experiment.It has certain guiding significance for the future research and production practice of this kind of motor.