Problem Modelling and Mesh Construction

Abstract

Setting up magnetics problems for solution by computer involves several tasks. First, the geometric shape of the device to be analyzed must be described to the computer, and a discrete numerical model must be created which satisfactorily approximates the real device. Next, the materials to be used in the analysis must be identified and their properties described. Finally, the boundary conditions and the excitation values must be defined. It is often necessary to compute a solution for each of several closely related cases, for example, to find the magnetic state of a device for various different values of exciting current; therefore, boundary conditions and excitations are usually prescribed several times, one set for each distinct physical case. Once the physical problem has been fully stated in this way, most CAD systems further require the user to stipulate certain purely system-related parameters, such as the type of equation-solving technique to be used or the accuracy levels desired. The entire ensemble of steps needed to set up problems in a form ready for solution is usually termed preprocessing. This chapter outlines typical preprocessing steps in CAD systems, omitting only the construction of material property curves which is described elsewhere in this book.