Research On Design Method Of Permanent Magnet Synchronous Motor With Adjustable Flux Leakage

In recent years,with the development of performance of permanent magnet,PMSM which takes the advantage of simple structure,high efficiency,high control accuracy is widely used in machine tool processing,aerospace,automotive drive system and other production and living fields.However,the constant excitation of the PMSM makes the air gap magnetic field adjustment difficult,limiting the range of weak magnetic speed.How to improve the efficiency of permanent magnet synchronous motor constant power operation and widen the speed range,is still the hot spot of the motor field research at present time.In this paper,based on the traditional PMSM,an adjustable leakage flux permanent magnet synchronous motor is proposed.The structure of this novel PMSM is introduced and the flux-weakening principle is introduced.The no-load equivalent magnetic circuit model is built.Firstly,we analyze the conductor in the slot that affects magnetic reluctance which passed by the magnetic flux generated by the permanent magnet.We build the force analysis model of the magnetic conductor,and use the finite element method to research on the variable rule of the electromagnetic force from aspects of the position of the magnetic conductor in the slot,the size of the magnetic conductor,the size of the permanent magnet,the air gap length,the turns of coils and the width of the magnetic bridge.Secondly,the rotor need to achieve flux-weakening speed and high output torque at the same time,we analyze torque of the motor.The effect of the electromagnetic parameters on the electromagnetic torque is calculated from the perspective of air gap length,coil turns,current,the size of PMs,and size of magnetic conductor.We analyze the effect of electromagnetic parameters on the fluctuation of motor torque.We analyze the no-load performance of the adjustable leakage flux PMSM.We research on the relationship between the no-load air gap magnetic density and the no-load back electromotive force(EMF)versus with the distance s(the magnetic conductor moves in the slot).We use finite element method to simulate the effect ofelectromagnetic parameters on the flux-weakening range of the motor.The no-load leakage coefficient of the PMSM is calculated.The inter-polar magnetic leakage coefficient is calculated from the aspects of the air gap length,magnetic conductor size and PMs size.Finally,the results of the finite element method are in agreement with the magnetic circuit method,which verifies that the maximum speed of the permanent magnet synchronous motor is three times the rated speed,the PMSM can achieve excellent flux-weakening and rated torque output.