MODELING AND ANALYSIS OF ELECTRIC AND MAGNETIC COUPLED PROBLEMS UNDER NONLINEAR CONDITIONS

In this paper the authors define a numerical method to solve nonlinear combined magnetic and electric problems using reliable general purpose calculation codes. This method has been applied to analyze the behavior of a busbar system built with a saturable steel enclosure and connected with an arbitrary external circuit. The enclosure magnetic characteristics have been determined by means of experimental tests executed by the authors. To analyze this electrical system, the skin and proximity effects in the massive conductors, as well as the load conditions of the external circuit, must be taken into account. The present formulation permits us to solve the previously described coupled problems by means of an iterative procedure. Using this technique, it is possible to solve separately the field and the circuit equations by means of specific codes. In particular, an iterative procedure it is pointed out so defined: for each estimated load condition, a finite element code has been used to evaluate the relating busbar cross parameters, taking into account the nonlinear behavior of the steel enclosure, while, for each assigned set of the busbar cross parameters, a circuit simulator has been used to determine the relating load conditions of the busbar. In addition, a specialized post-processor has been developed to manage the data flow between the calculation codes. The originality of this work is linked to the use of general purpose commercial software to solve the nonlinear magnetic and electric coupled problems.