As can be seen from TABLE I, for either DAB1 or DAB3, same transferring power Po can be realized by different combinations of (d, L, Ф), which defines the operating point of the system. Different operating points result in different optimized designs of transformers. Hence, to compare the design of single and three-phase transformer, corresponding operating points of DAB1 and DAB3 are found first. Assumptions are made, with reference to [23], indicating DAB1 and DAB3 to: