Research On Electrodynamic Force Distribution And Durability Of Winding Insulation Of EMU Vehicular Transformer

The lightweight of electric traction system has been admitted as a prospective development direction of high-speed EMUs(electric multiple units)in China.The vehicular transformer is the heaviest single electrical equipment on EMUs.The vehicular transformer with large weight has put a heavy strain on further increasing the speed of trains and caused irreversible degradation of key components of EMUs.Therefore,the lightweight of vehicular transformer has been assigned as a top priority initiative.Light dry-type transformer is the main potential solution to the lightweight of EMUs.The windings of the new dry-type transformer are cast by epoxy resin insulation material,which has low mechanical resistance strength.Train operating conditions and operating environment are complex,transformer has potential short-circuit impact hidden danger,vehicular transformer windings are subjected to huge electrodynamic force under the short-circuit impact.Therefore,it is necessary to explore the electrodynamic force distribution and durability of winding insulation of dry-type transformer.Therefore,this paper mainly considers the time-varying characteristics of electrical parameters,builds a multi-physical field coupling model of magnetic field-solid mechanics of vehicular transformer,and explores transformer electromagnetism distribution and electrodynamic force distribution.The mechanical resistance strength of insulating materials was explored by tensile test and fatigue test.The electrical insulation performance of insulating materials was explored by dielectric loss test.The main research contents of this paper are as follows:In this paper,a 3D model of magnetic field-solid mechanics coupling of vehicular transformer is constructed by COMSOL finite element software.Then,the current test experiment of EMU train is carried out,and the current curve data that changes with time under different operating conditions including train starting,variable acceleration,uniform acceleration,uniform deceleration,variable deceleration are measured,and the harmonic processing of the test data is carried out by Fourier transform.Based on the experimental data and finite element model,the transformer electromagnetism and electrodynamic force distribution characteristics and its development law under different operating conditions are explored.Then,the electrodynamic force evolution mechanism of vehicular transformer under short-circuit impact is analyzed.The distribution characteristics and development law of electromagnetism and electrodynamic force of vehicular transformer under short-circuit impact are analyzed by finite element model,and the fault development mode of winding under short-circuit impact is analyzed.Finally,based on the maximum short-circuit electrodynamic force,the durability of epoxy resin insulation material was explored,the tensile strength test and fatigue test of epoxy resin were carried out,and the tensile strength limit and fatigue life of insulation material were obtained.Considering the cumulative process of insulation failure under multiple short-circuit impact,dielectric parameters of epoxy resin before and after fatigue deterioration were tested,and the electrical insulation performance of insulation material was explored,which provided reference for fault prediction and life prediction of vehicular transformer.