| Ferromagnetic materials such as silicon steel sheet deforms under the action of magnetic field due to magnetostriction which drives the vibration of the whole structure.Transformer is made of silicon steel sheets thus it deforms periodically.Microwave ovens are more likely to generate vibration and noise under the alternating excitation of the transformer because the main structure is board,it is a typical structure vibration caused by magnetostriction.The magnetostriction of transformer is analyzed in this paper,one model of microwave oven is taking as the analysis object and the finite element structural model of it is established.Two kinds of side panel is designed according to the characteristics of excitation and the design of the panels,as a result,the vibration response and noise is reduced.Firstly the circuit is analyzed and both the high and low current of the transformer is obtained by simulation using COMSOL,then the magnetic distribution of the transformer is obtained according to the principle of electromagnetic induction,so the deformation of the transformer can be calculated by magnetostriction constitutive equation and the excitation force to the bottom plate can be obtained too.The current at both ends of the transformer is measured,the data is basically consistent with simulation analysis which proved that the simulation analysis is correct.Then the microwave oven is disassembled and measured,so geometry model of each part is established according to the data by CATIA.Modal tests are carried out on both the upper panel and the side panel,so the vibration modes of the panel are obtained which contribute to accurate panel model.For further the full finite element model of the whole structure is constructed.Two improvements of side panel are put forward for the shortcoming which the vibration mode frequency of side panel is close to the excitation frequency of the transformer.The vibration displacement response of the three kinds side panel is simulated with software,the results show that the vibration amplitude decreases effectively.At last the simulation results of displacement are imported into LMSVirtual.lab for noise simulation,the results show that the vibration noise of the improved panel is reduced too. |
