Research On Magnetostriction Of Oriented Silicon Steel Sheet And Transformer Core Vibration And Noise

With the wide application of power electronic devices and non-linear or shocking loads,the pollution caused by interharmonics is becoming increasingly serious in power systems.Transformers,as an important equipment in power systems,have always been the focus of researches,but there are few studies on the phenomena of abnormal increase of vibration noise caused by interharmonic excitation.Based on the magnetostrictive measurement results of oriented silicon steel sheet,the core vibration displacement and noise characteristics under inter-harmonic excitation are analyzed in this thesis through multiphysics coupling simulation and experiments.The main research contents are:(1)Using a magnetostrictive laser measurement system,the magnetic characteristics,magnetostrictive characteristics,and noise levels caused by magnetostriction of B27R085 oriented silicon steel sheet were accurately measured under power frequency sinusoidal excitation.The effects of excitation frequency on the magnetostriction of silicon steel sheet and the A-weighted noise level caused by it are summarized.(2)Based on the measured data of the magnetostrictions of oriented silicon steel sheets,and the theories combining circuits,magnetic fields,solid mechanics,and sound field,the magnetic flux density,vibration displacement and surrounding noise level distribution of the transformer core model under power frequency sine and different interharmonics were calculated by simulation.The effects of Electromagnetic force and magnetostrictive force on vibration were compared.The influence of interharmonic frequency and content on vibration noise was obtained.(3)A transformer core vibration and noise measurement platform capable of generating any interharmonic excitation was built.The real-time vibration displacement waveforms and the amplitude changes of the surrounding noise levels of the core model under normal and interharmonic conditions were measured experimentally.The effects of excitation intermediate harmonic content and frequency on the core vibration displacement and ambient sound pressure level are summarized.Finally,the experimental results are compared with the simulation results.The reasonableness of the simulation model is verified within the allowable range of the project.