Actual Source Integral Artificial Boundary Method For Open Electromagnetic Field

Open boundary problems exist widely in electrical engineering. It is difficult to calculate it. Artificial boundary method converts an open boundary problem to a bounded problem with artificial boundary condition. The keys of the method are how to give veracious artificial boundary condition or design accurate approximative artificial boundary condition and to reduce the finite domain. The research of artificial boundary method is significancement in theory and practicality. The dissertation studied a new artificial boundary method named actual source integral artificial boundary method (ASIABM). The main research works were as follows.The dissertation proposed ASIABM and the coupling relationship of differential equation for finite domain and artificial boundary condition was build in the method. The artificial boundary condition was written as integral of first sources (origin field sources) and second sources (equivalent sources of media). The second sources had certain physical signification. They were expressed by differential of electromagnetic potentials. The second sources were calculated by (?)φ in electrostatic field. They were calculated by (?)×A in magnetostatic field. In eddy current field the second sources were calculated by (?)×A and (?)φ. In the method the finite domain could be decreased because the artificial bounary was located near the media and the domain was decomposed. The artificial boundary condition is veracious in form. There isn’t singular integral in the calculation of artificial boundary condition.GMRES iterative method was used to solve the equations of ASIABM while its coefficient matrix didn’t exist. By the iterative method electric potential on boundary was calculated in electrostatic field. Magnetic vector potential A on boundary was calculated in magnetostatic field. By the iterative method A·l on the edge of boundary element was calculated in eddy current field. The results indicated that the iterative method had high precision and converged rapidly.The computational precision of artificial boundary condition was studied when media were expressed by different second sources. In eddy current field, conductor was expressed by eddy current density, and magnetization was expressed by magnetization current density or magnetic dipole moment density. There is eddy current in ferromagnetic medium. That results in magnetization volume current. An axisymmetric model was calculated by ASIABM and 2D FEM separately. The results indicated that the calculation error of B was large when the medium was expressed by magnetization current density. The results were consistent with 2D FEM results when the medium was expressed by magnetic dipole moment density.The influencing factors for convergence of GMRES were studied. The results were as follow. Iterative times increased when the shape of media was irregular. Domain decomposition had little influence to convergence speed. When μr changed the convergence speed changed little in magnetostatic field. The convergence speed was faster when μr increased in eddy current field problem. Engineering problems were solved by ASIABM with its GMRES algorithm. The electric field of line insulators in extra-high voltage AC transmission project was calculated. Its results were consistent with reference. The problem of space magnetic field shielding of three-phase reactive coils was calculated and the shielding effect was given.