| In recent years, with the rapid innovation of the electronic power technology, intelligent electric spindle mechanism and new materials, the permanent magnet synchronous motorized spindle(PMSMS) in the continuous improvement has been widely concerned in the industry. The PMSMS has been applied in all fields by characterization of its smooth operation, small size and fast response. The vibration noise is the key to evaluating its quality. The electromagnetic noise is the main component of the vibration noise. Therefore, the research on the influence factor of PMSMS electromagnetic noise has important practical significance. In this paper, through the analysis of the vibration characteristics of the PMSMS, the main factors of influencing the electromagnetic noise are found. Meanwhile, through the improvement of the structural parameters of the motor spindle, the influence law of electromagnetic noise will be summarized. The main research contents are divided as following several aspects:Firstly, the models of main structures, such as the stator, casing and end cover of PMSMS, were established by the three-dimensional design software. The modal analysis of stator structure was made to analyze its modal frequency and mode of vibration by using ANSYS. The precision of the stator natural frequency was improved by the introduction of calculating method for composite elastic modulus. Through the harmonic response analysis of the stator, the resonance points were found. With the modal analysis, the natural frequencies of the stator were obtained. It is found that the natural frequency will increase with the increase of the outer diameter by calculation. Therefore, the resonance points were avoided and electromagnetic noise was reduced by changing the outer diameter of the stator. The natural frequencies of stator and casing with the base, radiating rib and end cover were calculated by using finite element method, which provides references for the simplification of the whole machine model. At last, the modal frequencies were determined by comparing the results of simulating modal analysis and experimental modal analysis.Secondly, for the reason that the main factor causing electromagnetic vibration noise is the radial electromagnetic force in the air-gap, In this paper, the radial electromagnetic force of 8 poles 36 slots PMSMS was mainly researched. The two-dimensional electromagnetic field of the PMSMS was established by ANSYS software. The air-gap magnetic field was solved by the time step finite element method. The flux density with the changing of time and space was obtained quickly and efficiently. The radial electromagnetic force in time domain and frequency domain was calculated by using the Maxwell stress tensor method. The harmonic and frequency spectrum were analyzed by using the data analysis software. Caused by the tangential electromagnetic force, the cogging torque has been considered as another factor of affecting the electromagnetic noise. Through the finite element analysis, the result is basically same as the rated torque, and the reliability of the two-dimensional magnetic field model was verified effectively.Finally, through the analysis of the main influence factors of the PMSMS electromagnetic noise, the main structure parameters that affect the electromagnetic noise of the PMSMS were improved, including the number of large and small pole of permanent magnet, the shape of the stator teeth and the air-gap length. As an example of a 4 pole 6 slot PMSMS, the influence laws of the rotor torque ripple and the radial electromagnetic force under different structure parameters were analyzed and compared, which provided references for weakening the electromagnetic noise of PMSMS. |
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