Abstract
The Bridge type converter magnetize transformer on positive and negative directions, while forward type converter magnetize transformer on one direction. For that reason, forward type converter is considered that it operate only in the first quadrant of BH curve. But the careful observation of the transformer voltages and currents brings us to the new understanding that the magnetizing current of the transformer flows not only to positive direction but also to negative direction, which derives the new theory that the transformer operate not only at the first quadrant of BH curve but also at the third quadrant. In this paper we probe the new theory by the analysis of magnetizing current and propose a new design method of transformer.
