The Magnetic Equivalent And Electromagnetic Vibration Analysis Of The Laminated Core Of The Laminated Core

Power transformer will produce low-frequency vibration and noise in the operation process,which will not only cause noise pollution and make the components loose,but also threaten the power supply reliability of power system.Core vibration is an important source of power transformer vibration and noise.In order to find an effective method of vibration reduction and noise reduction,it is necessary to study the causes of vibration.In this thesis,numerical analysis and experimental research are carried out on the corner overlap area of the core,which is the concentrated area of vibration.This thesis mainly studies from the following aspects:(1)In order to obtain the magnetic characteristic parameters needed for the numerical calculation of electromagnetic vibration in the lamination area,the magnetization and magnetostriction characteristics of silicon steel single piece under sinusoidal excitation are measured by SST300 magnetization characteristic measurement system and MST500 magnetostriction measurement system,which are in accordance with the international standards of IEC.In addition,the magnetization characteristics and magnetostrictive properties under DC bias are studied in order to apply the measured data of magnetic characteristics to the numerical calculation conveniently.(2)Based on the measurement results of the magnetic properties of silicon steel single chip,the equivalent magnetization curve of the overlap area is obtained by equivalent calculation of the magnetic properties in the overlap area and the equivalent magnetostriction curve is obtained by combining the magnetostriction curve.Then the equivalent magnetostriction curve is applied to the numerical calculation of the overlap area's local magneto-induced vibration.Besides,the numerical results are compared with those without considering magnetic equivalence.At the same time,the vibration in the overlap area of the square ring is measured by the vibration measuring device,which verifies the effectiveness of the equivalent method has higher accuracy.(3)Based on the weak coupling analysis of magneto-mechanical,a threedimensional numerical model of laminated core with overlap gap is established,and the Maxwell force in the overlap area of laminated core under normal working condition and DC bias condition is calculated quantitatively.At the same time,combined with the results of magnetostrictive force calculation,the contribution of the two kinds of forces to the electromagnetic vibration in the overlap area of laminated core is compared.The result shows that magnetostriction is the main cause of electromagnetic vibration in the overlap area.In addition,the electromagnetic vibration in the overlap area of the laminated core is calculated and analyzed considering the two forces at the same time.Through the experiment,the vibration displacement of a measuring point in the overlap area of square ring lamination core under normal working condition and DC bias condition is measured and the accuracy of the numerical calculation results is verified.In this thesis,the research on the local vibration of laminated core overlap area is carried out.The research content is beneficial to improve the calculation accuracy of electromagnetic vibration of laminated core,to accurately predict the noise level of transformer products,and to further put forward effective methods of vibration reduction.