Analysis Of Electromagnetic Vibration And Noise Of Low-power Permanent Magnet Synchronous Motor

Although the permanent magnet synchronous motor has the advantages of high power density, high efficiency and reliable operation,its vibration and noise hinders its further application. For the low-power permanent magnet synchronous motor, the electromagnetic vibration and noise of the motor is particularly prominent. It is necessary to study the electromagnetic vibration and noise of the low-power permanent magnet synchronous motor.The principle of the electromagnetic vibration and noise of the motor is that the radial electromagnetic force excites the stator system of the motor and the vibration of the stator system radiates noise. Two main reasons result in the electromagnetic vibration and noise of the low-power permanent magnet synchronous motor. The one is that the space order and the time frequency of the radial electromagnetic force produced by the air-gap magnetic flux density is complicated. The other one is that when the time frequency of the radial electromagnetic force close to the modal frequency of the stator system, which causes structural resonance. This paper takes the 540 W 4-pole 6-slot permanent magnet synchronous motor as the research object, bases on the theory of electromagnetism, structural dynamics and acoustics, and applies the analytical method, the finite element method and the boundary element method to the following research:Firstly, this paper calculates the time frequency and space order of the radial electromagnetic force under load by the analytical method. At the same time, the time frequency and space order of the radialelectromagnetic force are calculated under load via electromagnetic finite element simulation and two-dimensional Fourier transform. Compared with the calculation results, the time frequency and space order of the radial electromagnetic force calculated by the analytical method are same as the results calculated by the finite element simulation.Secondly, this paper conducts the modal analysis by the equivalent model of stator core, the equivalent model of winding, and setting up the reasonable contact. The study shows that the adding of winding, house case, end cover, and boundary condition can make the deformation of the radial modal modes of stator system smaller and the modal frequencies of stator system rise.Thirdly, an improved electromagnetic loading way of the concentrated force is used to simulate the electromagnetic vibration of the motor. The calculation results show that although the amplitude of radial electromagnetic force in low frequency band is larger, but the motor electromagnetic vibration in high frequency band is more obvious and observing the local natural vibration mode of the housing case or the rear end cover can quickly determine the cause of resonance.What’s more, the relationship between the electromagnetic vibration and the electromagnetic noise at the resonance frequency is analyzed by using the direct boundary element method. The analysis shows that the relationship can be determined intuitively via comparing the cloud of resonant acceleration of the stator system with the cloud of sound pressure level generated by resonance response. Meanwhile, the noise at resonant frequency tends to dominate the total sound pressure level of the measuring point in the whole frequency range.Finally, on the premise of not reducing the motor output torque,minimizing the radial electromagnetic force on the stator tooth surface is the target. The response surface model is established, which optimizes the parameters of the two kinds of stator teeth. As seen from the result of the optimization, the two stator tooth can lower the electromagnetic vibrationand noise, in which the three-segment tooth tends to do well in the aspect of electromagnetic vibration and in terms of electromagnetic noise the local eccentric tooth is better.