A. Design Objectives and Variables
For case study in this paper, core type transformers are selected as an example for both single and three-phase transformers. For single-phase one, two U cores are combined and half of the primary and secondary windings are wound coaxially on either leg of the core. Correspondingly, two E cores are utilized for the three- phase transformer, with the center posts processed so that all three legs have the same width. The primary and secondary windings of each phase are wound on each leg, also coaxially. The structures of single and three-phase transformer are shown in Fig. 4 and Fig. 5.