Permanent magnetism AC servo motor

The utility model provides a permanent magnetism AC servo motor arranged at a joint of an arc-welding robot. The permanent magnetism AC servo motor is characterized in that the servo motor comprises a circular stator which is arranged at the joint of the arc-welding robot and a rotor which is disposed inside the stator and coaxially arranged with the stator, wherein the stator comprises a circular stator core, at least two grooves and coils, the grooves are uniformly distributed on the surface of the stator core, and the coils in one-to-one correspondence with the grooves are winded in the grooves; and the rotor comprises a rotor core and at least two magnets, the rotor core is in an integrated circular structure, the outer surface of the rotor core is polygon-shaped, the portion where the center shaft of the rotor core and the circular middle portion of the stator are overlapped are embedded in the circular middle portion of the stator, the center shaft is in rotation connection with the stator, the surface of the center shaft is parallel with the outer surface of the stator, and the magnets respectively serving as N poles and S poles are uniformly distributed on the outer surface of the rotor core.