On the basis of the analysis of static economic load rate, a dynamic optimal economic load rate of transformer is provided, which is the basis for selection of trans-former capacity.

This lack of static, DC offset current in the output transformer means that the core can be made smaller, because it requires no air gap to prevent core saturation from the static DC offset current.

A static var compensator of hybrid transformer type, which has both capacitive and inductive reactive power, is also presented in this paper.