I. Introduction
The difficulty in achieving the optimum balance between the transformer cost and performance is becoming even more complicated nowadays, as the main materials used in transformer manufacturing (copper or aluminum for transformer windings, steel for magnetic circuit) are variable stock exchange commodities and their prices are modified on a daily basis. Techniques that include mathematical models employing analytical formulas, based on design constants and approximations for the calculation of the transformer parameters are often the base of the design process adopted by transformer manufacturers [1].