PURPOSE: To increase thermal conductivity between a stator frame and a stator core, and to lower the whole temperature rise by bonding the boundary sections of the arcuate section and notch section of the stator core through welding by the stator frame.

CONSTITUTION: A stator core 13 is formed through welding by laser beams to a stator frame 11 in the boundary sections of arcuate sections 13d and notch sections 13c, and bonding sections 23 are formed continuously in the axial direction extending over overall width size of the stator core 13 two by two to each arcuate section 13d. When electricity is conducted through the coil 14 of a stator 12 and the temperatures of the coil 14 and the stator core 13 are elevated, the heat of sections corresponding to the arcuate sections 13d is transmitted over the stator frame 11 through the arcuate sections 13d, and dissipated to the outside from the outer circumferential section of the stator frame 11. On the other hand, the greater part of the heat of sections corresponding to the notch sections 13c of the stator core 13 are transmitted to the stator frame 11 through the bonding sections 23, one parts are transmitted over the stator frame 11 through the arcuate sections 13d, and both heat are dissipated to the outside from the outer circumferential section of the stator frame 11.