Research On Vibration Of Permanent Magnet Brushless DC Motor

With the development of economy and society in our country,A large number of permanent magnet brushless DC motor(BLDC)used in all fields of our society.Such as the industries of home appliances,automotive and so on.The development direction of the BLDC is high speed,low vibration and low noise.The brushless motor in air conditioner,mainly installed in air conditioning compressor.And the compressor is the main vibration source of air conditioner,The vibration standard of the compressor has become one of the important indexes to evaluate the quality of the products.Therefore,it becomes more and more important to analyze the vibration problem of the BLDC in the compressor.In the working process of the permanent magnet brushless DC motor,the main sources of vibration are torque ripple that it is because of cogging effect,unbalanced electromagnetic force and eccentricity of the rotor.Therefore,this above points will become the focus of the research and analysis of the BLDC which is used in compressor.In this paper,the study object is the BLDC which is used in air conditioning compressor.The important content of first part is the influence of the electromagnetic field which because of the mechanical structure of the motor.The results show that:1.The fluctuation of radial and tangential magnetic induction intensity in the BLDC will be increasing with the slot opening gradually increase.2.Get the cogging torque,electromagnetic torque and unbalanced electromagnetic force of the motor by using Maxwell tensor method.And get the fluctuation of cogging torque and electromagnetic torque will be more and more big with the slot opening gradually increase.3.The unbalanced electromagnetic force will be increasing with the increase of the pole arc coefficient,and it will be decreasing with the increase of the air gap length.Therefore,it can obtain the dynamics source excitation data of BLDC.In the second part,will establish dynamic model of motor which include rotor-bearing-stator.Solving equations by the method of ode45.Obtain the figures of time-domain response,frequency spectrum and axis orbit.The results show that:1.The BLDC’s vibration amplitude will be decreasing with the decrease of the pole arc coefficient and the increase of the air gap length.2.With the eccentricity of rolling growing,the vibration amplitude of BLDC will be increasing.3.The appropriate eccentric initial angle of rolling rotor will reduce the vibration amplitude of BLDC.So,This part helps to understand the vibration law during the motor stable operation and effects of mechanical parameters on motor vibration.The research work of the paper will help the design and vibration reduction for the BLDC which is used in air conditioning compressor.And it have some theoretical and engineering value.