The utility model discloses a transformation device, especially to a low-impedance transformer which effectively reduces distance between windings of various sides of the transformer, lowers manufacture cost of the transformer and effectively fixes windings to ensure concentricity. Inner ceramic heads and outer ceramic heads are respectively arranged on the two ends of an inner isolation cylinder and the two ends of an outer isolation cylinder, and inner positioning stripe sets and outer positioning stripe sets are respectively fixed on the inner sides of the inner ceramic heads and outer ceramic heads Each of the inner positioning stripe sets at least comprises two inner positioning strips, of which the centers are mutually overlapped with each other, and each of the outer positioning stripe sets at least comprises two outer positioning strips, of which the centers are mutually overlapped with each other. Inner installation holes and outer installation holes are respectively arranged in the center of the inner positioning stripe sets and the outer positioning stripe sets. Insulating bosses are arranged on the axle centers at two ends of an iron core, a positioning post is arranged on each insulating boss and passes through the inner installation holes and outer installation holes, and end portions of the positioning posts are provided with fixing members. A top cover is arranged outside each outer ceramic head, and an oil filler hole is arranged in the top cover.