Magnetic field calculation of cylindrical exciting coil above conductive plates

In material nondestructive evaluation, the primary excitation magnetic field interacts with the conductive material, the secondary magnetic field produced by the induced eddy current inside the conductive material will change the distribution of magnetic field near the material surface, and the variations of magnetic field indicate the characteristic of material. The accurate expression for the magnetic field´s variation of the coil above conductive plates is derived in an integral form by means of the double Fourier transformation method. The same problem is also solved with the domain truncation method and the expression in the form of series is obtained. The two calculation results are compared and find that the solutions of the double Fourier transformation method are more accurate. For the domain truncation method, the computational accuracy depends on the selection of outer boundary and the number of summation terms, but larger outer boundary and more summation terms cannot always guarantee more accurate computational results. The validity of the solutions is demonstrated by comparison to results obtained with the finite element method.