Measurement And Demagnetization Of The Residual Flux In The Iron Core Of Power Transformer

The problem of residual magnetic measuring and weakening is a difficult problem in the power transformer.To solve the problem,this paper proposes a modified single phase transformer residual magnetic survey and weakening method,which is verified by numerical simulation and experimental measurements.Firstly,based on the basic theory and the basic characteristics of the ferromagnetic materials,this paper analyzes the causes of power transformer residual magnetism and the harm of power transformer residual magnetism.Secondly,the test method is derived based on equivalent circuit and mathematical method.And then by numerical simulation to determine the parameters of the experiment and the feasibility of the test method.Finally through the test to validate the above methods,and the feasibility of the method is validated.The method of residual magnetic weakening has been analyzed and the optimal residual magnetic weakening method is found through numerical simulation and experiment.This paper mainly studies the following aspects:To set up a numerical simulation of the circuit transformer equivalent circuit.Set the experimental parameters and change the residual magnetism by changing the current in the residual magnetic coil,and the appropriate positive and negative direct current excitation is loaded in the measuring coil.Using Magnet software to perform numerical simulation,the corresponding measurement current value of residual magnetism is obtained.To match the amount of residual magnetism and measuring the current change,find the relation between the current and the residual magnetism.With the ring core as the test object,the measuring circuit is built and the residual magnetic value is preset,loading the positive and negative excitation,and to capture the test current.The relationship between the current and the residual magnetism is found by processing the current,and it is found that the relative error of the residual magnetism obtained by the measured calculation and the preset residual magnetism is below 10%,which indicates the accuracy of the method.To weaken the remanent magnetization treatment of iron core,and to analyze the ac and dc method of two kinds of weakening the remanence method for theoretical analysis and numerical simulation,and then to physical test.The experiment sets up a control group,analyzing the effect of the magnitude,the period,and the other parameters to the test results,and finding the optimal way to weaken the residual magnetism.