| Permanent magnet assisted synchronous reluctance motor（PM-Syn RM）is widely used in various fields because of its high performance and low production cost.However,because the rotor structure of the motor is symmetric,the current angle corresponding to the maximum permanent magnet torque and the maximum reluctance torque is not equal,which means the two kinds of torque have different phases.This results in two kinds of torques that cannot be fully utilized.In addition,since the permanent magnet is placed in the middle of the magnetic barrier,the air gap flux density is low,the harmonic content is high,the torque ripple is high,the iron loss is significantly increased,and the motor efficiency can also be reduced.Therefore,the rotor structure consisting of a permanent magnet rotor and a reluctance rotor is designed in this paper and a new design idea is also proposed.This rotor structure can achieve the maximum torque current angle of the two torques to be equal.Therefore,the average torque and the torque density can be further improved when the volume of permanent magnet remains unchanged.The rotor structure has an obvious optimization effect on the torque ripple,air gap flux density and other electromagnetic parameters.The permanent magnet rotor and reluctance rotor can be designed separately,so the machining and the design of rotor are flexible.In order to verify the rationality of the hybrid rotor structure,a series of comparative analysis of permanent magnet synchronous reluctance motor with different rotor structure is carried out in this paper.The specific work of this paper is as follows:Firstly,this paper introduces the structure and mathematical model of the traditional PMSyn RM,which proves that the maximum torque current angle of the permanent magnet torque and reluctance torque is not the same through the torque formula of the motor.By analyzing the difference of mathematical models between permanent magnet synchronous motor（PMSM）and synchronous reluctance motor（Syn RM）,the operation principle and rotor topology of axial hybrid rotor are obtained,and the torque formula of axial hybrid rotor permanent magnet synchronous reluctance motor is proposed.Next is the design of the basic model PM-Syn RM.Compared with the permanent magnet torque,the reluctance torque of PM-Syn RM accounts for a larger proportion,the optimization design method takes magnetic barrier structure optimization as priority.This paper aims at the maximum motor d q axis inductance difference,salient pole ratio,electromagnetic torque and minimum torque ripple,and the main structural parameters of the motor rotor,such as the number of magnetic barrier layers,the air gap,the width of the magnetic isolation bridge,and the amount of permanent magnets,are analyzed by the finite element method.The optimal parameters are selected and the magnetic circuit structure of the motor is also analyzed.Then the axial hybrid rotors are designed based on the rotor structure of PM-Syn RM.The reluctance rotor is combined axially with the surface permanent magnet rotor and the interior permanent magnet rotor respectively,which form two rotor structures.The axial length proportional relationship of two rotors,axial assembly angle of reluctance rotor and the air gap magnetic separation distance between the two rotors are analyzed under the condition that the volumn of permanent magnet is constant and the maximum torque is generated.Finally,the electromagnetic characteristics of motors with two new rotor structures and the traditional PM-Syn RM are compared and analyzed.Similarly,through the finite element method,the performance parameters such as back EMF,air gap flux density under no-load conditions,torque characteristics and motor efficiency under load conditions are compared respectively,and then the superiority of the rotor structure is verified. |
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