Research On Electromagnetic Vibration And Noise Of Brushless Motor With Magnetic Pole Shift

At present,high-speed brushless DC motors are increasingly used in power tools and medical devices.In order to improve the motor production efficiency,the rotor pole of brushless motor is usually made of integral magnetic ring.Due to the magnetization device or the structure of the rotor,etc.,the magnetized region of each pole of the rotor may be uniform,which is called magnetic pole shift phenomenon.The magnetic pole shift will adversely affect the electromagnetic vibration and noise of the brushless motor,so the research of the subject has certain theoretical and practical significance.The research status of the effect of magnetic pole shift on electromagnetic vibration and noise of brushless motor was summarized,and the research content and chapter arrangement was put forward in chapter 1.In chapter 2,the analytical model of air-gap magnetic field of surface mounted brushless motor after magnetic pole shift was given,and the general expression of air-gap magnetic flux density of brushless motor after magnetic pole shift was obtained and discussed.Secondly,the interior rotor brushless motor with magnetic pole shift was equivalent to the surface-mounted rotor brushless motor,and the equivalent air gap flux density of the interior rotor brushless motor was calculated by analytical method,which was based on the idea of magnetic field equivalence.Finally,the finite element method was used to simulate and verify the above motor model.In chapter 3,the natural modes of brushless motor were studied,and the effects of different modal parameters on the natural modes of brushless motor were analyzed.The natural modes of two kinds of brushless motor were calculated by analytical and finite element methods respectively,and the influence of shell thickness,winding form and dip paint on the inherent modes of brushless motor was analyzed by three-dimensional simulation.In chapter 4,the effect of magnetic pole shift on electromagnetic vibration and noise of brushless motor was studied.Maxwell tensor method was used to calculate the radial electromagnetic wave of the brushless motor.The research shows that the magnetic pole shift will cause the harmonic of the electromagnetism of the motor to increase greatly,which will lead to the increase of the electromagnetic vibration and noise.In Chapter 5,the modal and electromagnetic vibration and noise experiments were carried out on the prototype of the brushless motor.The field experiment results verified the validity of the simulation results.And the full text was summarized in chapter 6.