Analysis Of Characteristics Of A Dual-system Locomotive Transformer In DC Power System

At present,the dual-current electric locomotive power supply system still exists in some countries,such as South Africa,Japan and America.The electric locomotive runs across the grid,in order to save space and reduce the amounts of equipment,when the locomotive is running on the DC power supply,the transformer serves as filter reactor,and its structure adopts four-split type.When the utility model is used as a reactor,four high voltage windings are connected in parallel,and the four low voltage windings are connected in series and are respectively connected with the two variable current loops.In theory,there are four kinds of connection modes which are in series with other winding of the four low voltage,and obviously,when the connection mode,load,the magnetic saturation degree differs,the corresponding inductance value also changes,and ultimately the filtering results will be affect.In addition,when the transformer is used as filter reactor,the different connection mode of low voltage winding will affect the transient process of inter network switching instants,and impulse current will produce in extreme cases.Therefore,it is necessary to make a deep analysis of the electromagnetic phenomena and parameters under various possible connection modes.The thesis which adopted the four split transformer conducted a deep research about a dual-current locomotive for export produced by China Railway Rolling Stock Corporation,namely establishing a magnetic field analysis model about the four possible connection method which is existed of the transformer low-voltage winding,comparing the magnetic field distribution of different paths and inspecting the situation of magnetic saturation.Through comparison and analysis,the connection mode which cascades the two windings towards reverse direction on the same iron core is chosen for the best method.Based on the field analysis,the matrix of inductance about high and low voltage windings is calculated,and furthermore,the equivalent inductance of two loop or single loop can be calculated.In the end,the paper simulates and analyses the transient process between DC power to AC power,and the results can provide the reference for the design.Through the analysis of the magnetic field distribution about four kinds of connection modes,a conclusion can be concluded that different magnetic flux path under different connection mode of the low voltage winding can generate different magnetic saturation situation.And under the circumstances,the NO.2 connection mode is selected.On the basis of the magnetic field analysis,calculating the inductance matrix and writing circuit equations can obtain equivalent inductance under different connection modes.In the end,the result is consistent with the magnetic field analysis.The analysis about electric locomotive which runs on the transient situation indicate that the four high voltage windings taking the open and parallel connection is reasonable.