Effect of Rotor Auxiliary Groove of Surface Permanent Magnet Synchronous Motor on Torque Ripple
Taking a 10-pole stator 30-slot surface permanent magnet synchronous motor as an example, auxiliary slots of different shapes, numbers and positions are respectively placed at the bottom of the rotor core and the permanent magnet below the permanent magnet, and various auxiliary slots are analyzed for the motor loading. The effects of torque ripple and average torque during operation summarize the variation of torque ripple with the size and position of the auxiliary slot. Finite element analysis shows that the provision of reasonable rotor core auxiliary slots and permanent magnet auxiliary slots can effectively attenuate torque ripple.
1 Introduction
According to the position of the permanent magnet on the rotor, the permanent magnet synchronous motors can be divided into three categories: surface type, built-in type and claw pole type. The surface rotor magnetic circuit structure is divided into two types: convex type and plug type.
On the other hand, torque ripple can cause motor noise and vibration, affecting the running performance and even life of the motor. Therefore, weakening the torque ripple is one of the main goals of permanent magnet motor design.
The data shows that the cogging torque expression of the surface convex permanent magnet synchronous motor derived from the energy method and Fourier decomposition is analyzed by the analytical analysis method, and the matching of the number of poles and the number of slots of the motor and the permanent magnet are analyzed. The influence of some design parameters such as pole arc coefficient and stator slot width on the cogging torque of the motor is deduced, and the optimal selection method of these design parameters is derived. In [2], an accurate subdomain analytical model of surface-embedded permanent magnet motor is established in a two-dimensional polar coordinate system, which is divided into three solving regions: stator slot subfield, air gap subdomain and rotor slot subdomain. The vector magnetic position of the subdomain is solved by the general solution, and the boundary conditions between the subfields are used to obtain the relevant harmonic coefficients, thereby providing conditions for the calculation of cogging torque.
It is proposed that different types of auxiliary grooves such as rectangular grooves, triangular grooves and semi-circular grooves are provided in the stator crown. The influence of various auxiliary grooves on the cogging torque is studied. It is found that the rectangular groove has the best effect on suppressing the cogging torque, and secondly It is a semi-circular groove and a triangular groove, and the cogging torque decreases as the depth of the auxiliary groove increases, and decreases first and then increases as the width of the groove increases.
In many literatures, the surface permanent magnet motor is equipped with auxiliary slots on the stator teeth to reduce the cogging torque. However, there is little literature on the influence of auxiliary slots on the cogging torque of the surface permanent magnet motor rotor. research. Moreover, the cogging torque is only one of the sources of torque ripple during motor load operation, and it is obviously not sufficient to only weaken the cogging torque. Therefore, for the permanent magnet motor with surface-inserted rotor structure, taking the 10-pole stator 30-slot motor as an example, the finite element simulation method is used to study the rotor core auxiliary groove below the permanent magnet and the auxiliary groove pair at the bottom of the permanent magnet. The influence of torque ripple during operation, through reasonable design of the auxiliary slot, undermines the torque ripple on the premise of ensuring a large output torque.
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