Numerical calculation of impedance for electric heating system in steel mills considering skin effect and proximity effect

MA Qiao; TONG Bing; TONG Xiangqian; ZHAO Teng; KOU Kaite; YANG Hongyin; WANG Yong

doi:10.3969/j.issn.1001-196X.2025.01.010

Abstract：The electric heating system in steel mills is a key equipment in the electric furnace steelmaking process.The calculation of conductor impedance in electric heating systems is crucial for improving the energy efficiency of electric furnace steelmaking.Due to the complex geometric model of electric heating systems and the significant influence of skin and proximity effects,traditional analytical methods are difficult to apply to conductor impedance calculations.A numerical calculation method for impedance of electric heating systems in steel mills is proposed based on finite element method,taking into account both conductor skin effect and proximity effect.Firstly,a three-dimensional electromagnetic field frequency domain model was established based on the theory of time-varying electromagnetic fields.Meanwhile,the boundary conditions at the interfaces of different conductor regions are given.Secondly,the FEM is used to solve the three-dimensional electromagnetic field model.The basic equations of the potential and magnetic loss potential functions are discretized based on the Galerkin weighted residual method.To verify the correctness and effectiveness of the method proposed in this article,the electric heating system of a 100 t electric furnace steel plant was taken as the test object.The research results show that based on the proposed method in this paper,the three-dimensional current density distribution and power frequency impedance of each submodule of the electric heating system can be obtained.The skin and proximity effects are more significant in short network copper tubes and water-cooled cables.The AC impedance of each submodule is much higher than the AC resistance,and the difference in AC and DC inductance is small.