A Study On The Vibration Characteristics Of Power Transformer Core Lamination Structure

Power transformer is one of the most important equipments in substation.Its noise level has become an important indicator to evaluate the quality of designing and manufacturing.The traditional noise control method is expensive,which is rnot conducive to the heat dissipation and maintenance of the equipments.However,there are little reports about the control of transformer noise at the electromagnetic vibration source and the stage of structure design.In this thesis,the transformer noise is investigated by examining the noise from outside to the inside of power transformers.It was started with noise evaluation in a substation.Then the vibration mechanism of core laminated structure is studied,so that to solve the problem of transformer vibration and noise radiation based on the modification of the transformer core structure.The main contents of this thesis are summarized as follows:First of all,the environmental noise evaluation in a 1000kV UHV substation is carried out,and the accuracy in the noise evaluation at the boundary of the substation is discussed.This part of study includes the selection of the best configutaion of the measurement points for sound pressure measurement,and the distribution characteristics of the noise in UHV substation.Then,the vibration distribution,sound radiation field,the attenuation properties of sound field and the influence factors of transformer's vibration and sound radiation are analyzed,and summarized the vibration characteristics of the sound source.Then the noise source is analyzed by studying the vibration mechanism of transformer structure.The transformer core is a typical laminated structure.Its vibration mechanism is investigated by using the beam structures consisted with Si-Fe sheets.The research includes the analysis of the frequency response functions of the bending and longitudinal vibrations of the laminated structure under different thickness and boundary conditions.The key factors affecting the frequency response of the laminated structure and the effect of the structural anisotropy on the vibration modeling.Through experimental and theoretical derivation,the empirical formula of equivalent bending stiffness and the equivalent modal loss factor of Si-Fe laminated bar are obtained.Finally,study is extended on the extraction of modal parameters,excitation current and vibration characteristics of the transformer core.This thesis may provide some theoretical support to the design of low vibration and noise transformer.