Characteristic Analysis Of Magnetostriction Of Electrical Steel And Vibration Of Iron Core

With the construction and development of UHV power grid,the vibration problem of the transformer and other power equipment is aggravated by harmonics and DC bias,which becomes the hidden danger of power system safe operation.To solve the problem of transformer vibration under complex excitation,from the magnetostrictive characteristics of silicon steel,combined with vibration experiment of iron core,the coupled magnetic-elastic force field equations are given.The vibration behavior of the iron core was simulated using the multi-physical field finite element simulation software-COMSOL.The main contents of this thesis are as follows:(1)An experimental platform for measuring magnetostrictive characteristics of silicon steel based on laser reflection principle is established.The magnetostrictive properties of the oriented silicon steel plate B30P105 under different excitation conditions such as sinusoidal,harmonic and DC bias are measured accurately.The influence of harmonic and DC bias on magnetostriction of silicon steel and the equivalent of A-weighted noise value is summarized.The effect of stress on the magnetostrictive properties is given by measuring the magnetostriction under stress.(2)An experimental platform for vibration measurement of iron core model is built.The vibration acceleration under different excitation conditions,such as sine,harmonic and DC bias,is measured,and the time domain waveform and spectrum diagram of vibration displacement are obtained.The trend of amplitude of vibration under different harmonic content and phase difference is given.The excitation current,vibration wave,main frequency and amplitude of vibration are studied.(3)Based on magnetostrictive measurement experiment and electromagnetic field and elastic mechanics,the mathematical model of magnetostriction is given.The magnetic field and elastic force field of iron core under different excitation are simulated by COMSOL,and the results are compared with the experimental results under sine excitation,and the validity of the magnetostrictive mathematical model and simulation method is verified.In this thesis,the vibration mechanism and vibration rules of power transformers under complex excitation are studied,which provides a reliable basis for the design and optimization of vibration and noise reduction.The vibration characteristics of iron core under different excitation conditions are studied.