Effect of Exciter Shape on Magnetic Field and Its Impedance in the Vicinity of a Multilayer Slab Conductor

摘要

If a coil is located in the vicinity of a slab conductor the distribution of magnetic field and the coil impedance will be changed due to conductor's electromagnetic induction. One of the main applications of changing in the electromagnetic field and coil impedance is in the non-destructive evaluation of conductors. In this study, effect of various coil shapes (i.e., elliptic and rhombic with different axes ratios) on the distribution of magnetic field was analyzed based on electromagnetic field distribution method which solves the Helmholtz equation in three dimensions semi-analytically. For solving an n-layer problem with several coil exciters, the boundary condition equations in between the two neighboring layers (and also the first and last layers opening to air) were arranged in a sparse matrix form. To solve this matrix, a suitable computer program was provided in MATLAB. Several example problems were solved showing the effects of elliptic and rhombic coil shapes on the magnetic field. The computed results were obtained considering several coil axes ratios. The effect of source frequency variations on the coil impedance was also analyzed and discussed. These computed results were given in suitable figures.