Relative advantages of one-phase and three-phase transformers

In considering the relative advantages of three-phase and one-phase transformers it will be assumed at the outset that the three-phase transformer is to be compared with a group of three one-phase transformers whose aggregate output is the same as that of one three-phase transformer; for it will be admitted at once that a comparison between one one-phase transformer and one three-phase transformer of the same output would be all in favor of the one-phase transformer. On this assumption, the advantages of the three-phase transformer over the one-phase group are as follows: