The Research Of New Demagnetization Method On Traction Transformer Of Multi-system Electric Locomotive

At present,the power supply system of Chinese railway transportation is basically divided into two kinds:AC power supply system(25kV/50Hz)and DC traction power supply system(1.5kV、750V).AC traction power supply system is used in main line railway and interurban railway.DC traction power suppl y system is used in urban railway system.With the development of our country’s economy,it’s urgent to use multiple-system electric locomotive to solve the problem of rail transit interconnection.In the dc power supply system,the traction windings used as dc filter inductor,because it is more economic.As a result,when disconnect the dc power grid switch to connect the ac power grid,the residual magnetism in iron core can cause serious inrush current.Therefore,it is of great significance to study th e demagnetization of traction transformer of multiple-system electric locomotive.This paper mainly has carried out the following research work:(1)The development situation,tendency and existing problems of our railway transportation are introduced,so we know the multiple-system electric locomotive has a broad prospect in China,and the abroad situation of multiple-system electric locomotives is introduced.In addition,for the problem of traction transformer remanece of multiple-system electric locomotives,the present research status and disadvantages at home and abroad of demagnetization and excitation inrush current suppression are also introduced(2)The topological structure of main circuit system on multiple-system electric locomotive and its working principle are introduced through introduce the main circuit system of the dc and ac system electric locomotive.Meanwhile,this paper especially analyzed the structure of traction transformer of multiple-system electric locomotive and the wiring schemes of traction windings used as dc filter inductor.Moreover,it also analyzed the influence of different wiring schemes on magnetic potential distribution in iron core,and established the simulation model on ANSYS to verify the analysis.(3)Firstly,the principle of residual magnetism of traction transformer of multiple-system electric locomotive and its harm are analyzed through analyze electromagnetic properties of the magnetic materials and the principle of remanence generating,meanwhile the mechanism of the inrush current caused by residual magnetism and the suppression methods are analyzed Therefore,according to the characteristics of traction topological structure in multiple-system electric locomotive,using the devices of the traction system itself,a new method——LC plus AC/DC Converter(traction winding,dc-side capacitor and four-quadrant rectifier)for demagnetization is proposed.According to the characteristics of the demagnetization circuit,the control strategy of the capacitor Voltage over zero is proposed,which produces the demagnetizing current of oscillation attenuation.In addition,in order to provide theoretical reference on matching of demagnetization parameters the influence of the demagnetization parameters is in-depth analyzed(4)Based on the system parameters of the 20 E multiple-system electric locomotive designed by CRRC,the simulation model of the new demagnetization method on traction transformer is established.The simulation results of demagnetization current show that the control strategy of the capacitor Voltage o ver zero is feasible.The analysis of the residual magnetism before and after traction transformer demagnetization and hysteresis loop proved that the new demagnetization method——LC plus AC/DC Converter is effective and feasible.Finally the simulation results of demagnetization parameters proved that the analysis of parameters’ influences is right.