The Analysis Of The Electrodynamic Force Of Electric Arc Furnace Transformer Compensation Winding

The EAF transformer,the core system of smelting industry,plays an important role in energy conversion,and its safety performance determines the stability and reliability of the entire system.In recent years,with the rapid development of electric arc furnace industry,electric arc furnace transformer capacity increases very fast,but the number of accidents increased year by year.According to relevant statistics,due to the damage of compensation windings,arc furnace transformer running 3-5 years has been burned as much as 27 units in the entire northwest region of the smelting plant in 2013,which caused huge losses to smelting enterprises.This study aims to explore the internal reasons why the arc furnace transformer is very easily to be damaged,and propose solutions,which has important theoretical and engineering value.This paper described the load characteristics of the electric arc furnace system,summed up the approach to build an electric arc furnace load models.Based on the chaotic essence of the arc furnace load,using modulation principle,this article proposed an electric arc furnace load model using asymmetric Chua chaotic and analyzed the load characteristic curve.Secondly,based on the model of the arc of chaos,added AC power,electric arc furnace transformers,filtering devices and other modules,this paper built the electric arc furnace system and got current waveform of each transformer winding through simulation,then obtained the various fundamental and harmonic rms and phase by Fourier analysis.Then,this paper studied for the characteristics of the transformer leakage magnetic field.Built a 8.5MVA arc furnace transformer model in the ANSYS software,loading fundamental and harmonic load current excitation,through field-circuit coupling and analyzed the variation regularity of both the axial leakage flux and radial leakage flux at a certain time point and throughout the time domain.Finally,according to the analysis of leakage magnetic field in the arc furnace transformer,this article analyzed the variation regularity axial electrodynamic force and radial electrodynamic force at a certain time point and throughout the time domain.The results showed that:when the electric arc furnace transformer only load the fundamental,the frequency of axial force and radial force of compensating windings is doubled,and the axial force direction is always pointing to the middle of the winding,while the radial force becomes negative multiplier alternating pulsating electric power.When loading full current,the variation of axial force in the compensation winding is similar to load only the fundamental.Because of the harmonic,the waveform of radial force is distorted,and alternated positive and negative.Therefore,the fixture of compensation winding in the electric arc furnace transformer must build more.Otherwise after 3-5 years of wear insulated,transformer will become easily to burn out.This study shows that,the multiple frequency and alternating negative and positive of the electrodynamic force is the reason of compensating windings burned.