To realize a significant energy-saving effect by changing the procedure but not using any excessive material.

Five taps 6 are attached between 6,450 V and 6, 750 V in the service range. Pitch 75 V is raised or lowered by about 1.14% with respect to the standard voltage by adjustment of one tap. If the voltage can be adjusted, iron loss, copper loss, and load loss can be reduced even in a conventional transformer, and if a new material is used, the iron loss can be further reduced, and the copper loss and circuit loss can also be reduced significantly.