Abstract
This paper proposes a method of analyzing three dimensional magnetic field of a system containing coil currents and magnetic substances using virtual currents. Various methods have been presented for analysis of three-dimensional static field of open boundary space, but, in a large-scale problem, the size of computation easily exceeds the acceptable limit of computing time and the capacity of a machine. The basic idea of the proposed method is to divide the whole region into interior and exterior region with an artificial boundary and to substitute virtual currents for source currents and magnetic substances within the boundary. The use of virtual currents reduces the number of elements for the analysis and shortens computing time while maintaining accuracy of analysis. In this paper, a method of determining virtual current is proposed and principal parameters of virtual currents which affect accuracy of analysis are examined. The conditions under which the virtual current method can be applied are examined through analysis of errors introduced by virtual current method. This method has been applied to analyze magnetic shielding of a magnet for magnetic resonance imaging. This example proves that the proposed method is effective in reducing scale of analysis and computing time.
