MOM formulation for nonlinear low-frequency analysis in the time domain

A formulation of the method of moments for the analysis of nonlinear low frequency problems is presented. The examined system is subdivided into elementary volume elements whose nonlinearity is taken into account by means of the magnetizations M. Considering the nonlinear constitutive equation H=H(B) a nonlinear algebraic system of equations is obtained. By combining Gauss law and current continuity at the boundaries among regions with different conductivity a set of equations is obtained. Writing Ohm's law inside the conductive regions another integral equation set that allows the determination of the conduction current and surface charge unknowns is obtained. The method of moments is then applied to this system of equations. The use of pulse functions as subsection bases allows a quick matrix set up especially when regular volume shapes are selected. Calculated results are compared with results obtained with other methods.