Vibration Analysis Of Interior Permanent Magnet Brushless DC Motor

With the study of permanent magnet brushless motors more and more perfect,permanent magnet brushless motor are widely used in various fields of engineering.The current international generally believe that permanent magnet brushless motors instead of brushless motors will be the future development of a motor trend.The interior permanent magnet brushless DC motor is selected as the drive motor within the rolling rotor compressor used in air conditioning.Since the motor is placed inside the compressor,the rolling rotor of the working part of the compressor is connected to the rotor shaft of the motor,the vibration of the motor will affect the overall system vibration.Therefore,it is greatly important to study the vibration problem of interior permanent magnet brushless DC motor.In this paper,we will study the influences of magnetic torque and unbalance magnetic pull which are induced by the motor magnetic field on the motor vibration research,the main contents are:The first part is divided into two chapters,studying the eccentric magnetic field generated inside the motor from two aspects——analytic method and finite element method.First of all,obtain the electromagnetic torque and the unbalanced magnetic pull by the analytical method.Then analyze the magnetic field inside the motor by finite element method using Ansoft Maxwell software.The results obtained are basically consistent with the analytical results and verify the accuracy of analytical method.Study the variation of electromagnetic torque and unbalance magnetic pull under different eccentricity conditions.The results show that when the eccentricity increases,the mean value and magnitude of electromagnetic torque and unbalance magnetic pull increase.The unbalance magnetic pull mainly produces double frequency component,and the eccentricity has no effect on the frequency distribution.The second part is based on the first two chapters of the research results studying the vibration problems and take the electromagnetic torque and unbalanced magnetic pull as the exciting force.Simplify the model and establish the dynamic and torsional coupling equations of the rotor-bearing system.solve the dynamic equations of the motor by using The fourth-order Runge-Kutta method and MATLAB software and the time-domain and frequency-domain responses and the motor rotor axis locus are obtained.According to the results,it can be seen that bending vibration and torsional vibration affect each other.Increasing the dynamic eccentricity of the motor,increasing the motor speed and increasing the mass eccentricity of the rolling rotor will lead to the increase of the bending vibration amplitude.However,the rotation speed increases,the torsional vibration is weakened.And the eccentricity of rolling rotor has little effect on torsional vibration.