Analysis Of Effect Of Rotor Eccentricity On Vibration Characteristic In Small Induction Motor

Induction motors are widely used in marine auxiliary as power source and vibration and noise control of them is a research focus.Rotor eccentricity is of great influence in the vibration and noise of motor pumps.On one hand it distorts the electromagnetic field distribution in the air gap and change the electromagnetic excitations.On another hand the distorted electromagnetic field has an effect on the eccentricity condition and finally forms magneto-mechanical coupling vibration.In this dissertation the mapping relation between rotor eccentricity and induction motor vibration is researched.The main contents in this dissertation are as follows:The electromagnetic excitation is researched by analytical method to analyze the order and frequency characteristics under different eccentricity kinds.The result shows eccentricity will lead to a series of additional force waves which share conterminous order and frequency and the force waves whose order equals to one will produce unbalanced magnetic pull.The numerical calculation of electromagnetic field under eccentricity is completed with finite element method.Electromagnetic excitations under different eccentricities and loads are calculated to validate and amend the analytical result so that a method which can acquire the spatial distribution of electromagnetic field with arbitrary eccentricity is developed.The magneto-mechanical model is built by FEM to calculate the rotor dynamic response of motor shafts.The electromagnetic field is calculated by the position of rotor and the position is decided by the unbalanced excitations.The result indicates that eccentricity caused by stator deviation and misaligned shafts will lead to a large number of low-order force waves which may excite low-order stator modals and deteriorate the vibration condition.The response of induction motor with eccentricity is predicted and validated.The effect of different excitations is separated by an excitation-separated experiment bench to acquire the axis orbit and vibration response.Then the FEM modal of bench is amended by transfer function analysis and the excitation is computed based on the axis orbit to calculate the response.The result by simulation coincides well with the experiment result so that the effectiveness of the magneto-mechanical modal is validated.