PURPOSE: To improve a reliability with a compactness as well, by means of applying to maximum the advantageous point of a curved surface case.

CONSTITUTION: A connecting lead wire support plate 8 is constructed into a shape of curved surface with a curvature approximating the outside diameter of a winding 2a to 2c, by the method of rolling or press bending. Said support plate 8, by utilizing a delta-shape space between the windings 2a to 2c or a space between the side leg and the winding 2a, is fixed to the top and bottom core tightening metal. A tap lead wire 5, drawn out from each of the windings 2a to 2c, is arranged in a location along curved surfaces of said support plate 8, further with a fixing of the tap lead wire 5 made in some points to the insulating plate 8 by a lead wire fixing insulator like insulating sleeve.