AC motor designed to ensure high efficiency in operation

An ac motor comprising:

• a rotor having rotor magnetic poles which are N-poles and S-poles arranged alternately along a circumference thereof;
• a stator having N stator pole groups made up of magnetic poles arranged along a circumference thereof, the N stator pole groups being shifted in a circumferential direction of said stator relatively from a preselected reference one of the rotor magnetic poles by different angles, respectively, on a pole basis;
• and
• a plurality of looped windings each of which extends in a circumferential direction of said stator, the looped windings being disposed adjacent each other in an axial direction of said stator in relation to the N stator pole groups, respectively,
• wherein a number P of the rotor magnetic poles and a number M of the magnetic poles of said stator are selected to meet a relation of M<(P/2)×N.