PURPOSE: To enable an electrostatic shield ring to be supported positively and easily and reliability in terms of insulation to be improved by clamping the electrostatic shield ring and a supporting piece from a winding side at a position where electric field is weak by an insulation bolt for forming one piece and by fixing an edge part of the supporting piece to a winding by a winding press.

CONSTITUTION: In electrostatic shield rings 3A and 3B, a screw hole is provided at a position where electric field is weak on a junction surface with supporting pieces 6A and 6B, a penetration hole is provided at a position of the supporting pieces 6A and 6B corresponding to this screw hole, and then insulation bolts 7A and 7B are inserted into it, thus screwing into the screw hole. Namely, the electrostatic shield rings 3A and 3B are in one piece with the supporting pieces 6A and 6B by clamping from the winding side by the insulation bolts 7A and 7B. The supporting pieces 6A and 6B are extended in radius direction of windings 1 and 2 and are fixed to the windings 1 and 2 by a winding press 5 where a groove is formed matching the shape, thus eliminating a protruding object which causes partial discharge to be produced on a surface of the electrostatic shield rings 3A and 3B and enabling reliability in terms of insulation to be improved.