Study On The Influence Of Rotor Eccentricity On The Operating Characteristics Of Low Speed Permanent Magnet Synchronous Motor

Low Speed and Direct Drive Permanent Magnet Synchronous Motor（LSDDPMSM）is widely used in industrial production because it eliminates the reducer in asynchronous motor drive and adopts permanent magnet excitation.It has the advantages of high efficiency and stability,energy saving and environmental protection,easy maintenance and so on.In the actual production of LSDDPMSM,due to the errors in production and assembly,the center axis of stator and rotor cannot completely coincide,so the motor rotor is easy to deviate from the axis.At the same time,because the motor shaft is directly connected with the load,long-term operation is easy to cause bearing wear,sinking of rotor center of gravity,and rotor eccentricity.This thesis deeply studies the influence of rotor eccentricity on the operation performance of LSDDPMSM,mainly studies the influence of rotor eccentricity on motor cogging torque,air-gap flux density,loss and radial magnetic pull,and studies the vibration and noise caused by unbalanced magnetic pull caused by rotor eccentricity,mainly including the following contents:Firstly,based on the subdomain method,the boundary conditions and the basic equations of magnetic field distribution between the subdomains of the motor are established,and the eccentric magnetic field distribution of the motor rotor is analyzed by solving the two-dimensional magnetic field analytical model.Secondly,combined with finite element simulation,taking a 72 slot 60 pole LSDDPMSM as an example,the effects of rotor eccentricity on motor cogging torque,output torque,stator loss and air-gap flux density are studied,and the effects of rotor eccentricity on the electromagnetic performance of LSDDPMSM are summarized.Then,in order to study the electromagnetic force characteristics of the motor under eccentricity,this thesis establishes the analytical model of the radial electromagnetic force of the rotor eccentricity based on the magnetic potential permeance method,deduces the source,spatial order and frequency characteristics of the electromagnetic force,calculates and analyzes the unbalanced radial electromagnetic force density under the rotor eccentricity combined with the motor finite element model,and finally summarizes the influence of the rotor eccentricity on the radial electromagnetic force density of the motor.Finally,in order to study the influence of radial electromagnetic force on motor vibration and noise under rotor eccentricity,the modal frequency and vibration mode of the outer rotor of the motor are analyzed by finite element software,and the electromagnetic field calculation results are introduced into the outer rotor housing model for harmonic response analysis,the electromagnetic vibration results are solved,and the vibration characteristics of the housing under rotor eccentricity are analyzed.Using the noise calculation module of finite element software,the sound pressure level distribution on the surface of outer rotor sound cavity is obtained,and the influence of rotor eccentricity on motor noise is summarized and analyzed.