Stator terminals are fastened between head portions and coupling seats in a state of surface contact by screwing relay members onto external screw thread portions of output terminal bolts. Three-phase wire terminals are fastened in a state of surface contact to end surfaces of the relay members at opposite ends from the coupling seats by screwing nuts onto the external screw thread portions of the output terminal bolts. In addition, insulating tubes are interposed between the relay members and extraction apertures so as to cover outer sides of the relay members.