Research On Radial Electromagnetic Force And Vibration Noise Of External Rotor Permanent Magnet Synchronous Motor

The external rotor permanent magnet synchronous motor not only has the advantages of permanent magnet motor of high efficiency,high energy density and high power factor,but also has the advantages of large moment of inertia and large output torque,which makes it widely used in electric vehicles,robots,fans and other fields.With the improvement of stability and safety requirements in the operation of the whole machine,the problem of electromagnetic vibration and noise of external rotor permanent magnet synchronous motor has become increasingly prominent.The radial electromagnetic force in the air gap is the main source of electromagnetic vibration and noise.Therefore,it is necessary to study the radial electromagnetic force and electromagnetic vibration and noise.In this thesis,a 3k W external rotor permanent magnet synchronous motor is taken as a prototype,and the generation mechanism of the radial electromagnetic force,vibration and noise characteristics and suppression methods are studied,as well as the variation law of the radial electromagnetic force and vibration and noise when the eccentric fault occurs.Firstly,the two dimensional field-circuit coupling finite element model of the external rotor permanent magnet synchronous motor was established.The electromagnetic performance of no-load and rated load conditions were simulated and analyzed respectively,and verified by prototype test.On this basis,the source of radial electromagnetic force of external rotor permanent magnet synchronous motor and the spatial and temporal harmonic order of radial electromagnetic wave are analyzed theoretically and verified by simulation.The three-dimensional structural field finite element model of the external rotor was established,and the mode and vibration mode of the external rotor were calculated.By solving the coupling finite element model of electromagnetic-structural-noise,the electromagnetic vibration and noise characteristics of the external rotor permanent magnet synchronous motor were obtained.Secondly,three kinds of stator structure which can suppress the radial electromagnetic force and electromagnetic vibration noise of external rotor permanent magnet synchronous motor are proposed,namely,the migration structure of the tooth tip,the three-segment arc structure and the new structure of the tooth tip based on the sine distribution of the no-load electromotive force.The suppression principle of the three stator structures is analyzed theoretically,the electromagnetic performance,air gap flux density,radial electromagnetic force and electromagnetic vibration and noise characteristics of the external rotor permanent magnet synchronous motor under the three kinds of stator structure are analyzed and compared with the original structure,and the effectiveness of three kinds of stator structure is verified.Finally,the coupling finite element model of electromagnetic-structural-noise with different eccentricity when external rotor permanent magnet synchronous motor occur static eccentricity fault and dynamic eccentricity fault are established respectively.The radial electromagnetic force and electromagnetic vibration and noise under static eccentricity fault and dynamic eccentricity fault is simulated and analyzed.The change of electromagnetic performance,air gap flux density,radial electromagnetic force and electromagnetic vibration and noise characteristics are obtained when motor occur static eccentricity fault and dynamic eccentricity fault.