Coupled Electromagnetic and Heat Analysis of a ZnO Disk with the FDTD Method in the 2D Cylindrical Coordinate System

If a lightning current with a long wavetail flows in a zinc-oxide (ZnO) disk, the ZnO disk is heated and might be molten. In addition, in manufacturing process, the ZnO solidifies from the periphery to the center. Therefore, the ZnO resistivity is higher near the periphery and lower near the center. This inhomogeneous resistivity may cause the melting and or cracking of ZnO disk when a lightning current flows in the ZnO element. Although coupled electromagnetic and heat analysis of ZnO disks with the finite-difference timedomein(FDTD) method in the three-dimensional coordinate system have been carried out as of today, the maximum observation time is only about several tens of microseconds even with significant computational time and memory. In this paper, the electromagnetic and heat of a <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$\mathbf{1 5}$</tex>-mm-thick <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$\mathbf{Z n O}$</tex> disk are analyzed with the FDTD method in the two-dimensional cylindrical coordinate system for a lightning current. Influences of the inhomogeneous resistivity of the ZnO disk on the generated heat are particularly studied.