Transient Study Of Multi-split Transformer Based On "Field" And "Path" Analysis Methods

Locomotive transformer is an important equipment in electric locomotive.This paper takes a four-split transformer as an example,the transient analysis of no-load closing,single winding short circuit and interturn short circuit was carried out.The analysis method is field and path independence but in combination,the magnetic field analysis based on ANSYS is carried out first,on this basis,the port voltage and current under the steady-state condition are obtained,the impedance parameters of the equivalent circuit are obtained,write down the differential equations to solve the transient properties.When using ANSYS software for field analysis,established the "field-path" coupling model.In general,in a mathematical model that describes the distribution of magnetic fields,second order partial differential equations,the source of the "magnetic field" is the "current density",But the first known transformer is usually the applied voltage on the primary side,Therefore,when take the voltage as the"source",based on the equations that describe the distribution of the field,the corresponding circuit equation should be added.This is called "field-path" coupling.Through the "coupling"analysis of the steady-state no-load condition of the transformer,The no-load voltage of the secondary side is consistent with the design value,which proves the correctness of the analysis method adopted in this paper.This paper explores the following aspects:the axisymmetric "field-circuit" coupling analysis model of transformer 1/2 entity was established,No example of three-dimensional"field-path" coupling analysis has been found in the current literature,In this paper,an axisymmetric model is established by taking half of the transformer structure,namely an iron core column.the "field-path" coupling method is used to analyze different working conditions(No-load closing,sudden circuit and turn-to-turn short circuit,etc)The steady-state current voltage at the port is obtained,and the parameters of the equivalent circuit are obtained(Resistance,reactance,or inductance);Write differential equations for solving equivalent circuits in different working conditions.To sum up,this paper proposes a method combining "field" and "road" to analyze the transient state of different working conditions.One of the outstanding advantages of the method proposed in this paper is When simulating the short-circuit between transformer windings,it is convenient to consider different windings(high or low voltage),different parts(upper,middle and lower end of windings)and different turns,this is the current research methods in this respect can not be compared.There is no doubt that the method presented in this paper does not take into account the nonlinearity of ferromagnetic materials,It is completely feasible in theory.Of course,the method needs to be further improved,such as the establishment of three-dimensional"field-path" coupling analysis model and the consideration of nonlinear steady state of ferromagnetic materials.