US Patent 7960886 Rotating electric machine

A rotating electric machine includes a stator having a plurality of winding phases formed by distributed winding, a rotor having a plurality of magnetic poles and an outer circumference facing the stator, a first groove formed in the outer circumference of the rotor, a second groove formed in a position opposite to reference magnetic poles closest to the first groove, of the magnetic poles, with respect to the first groove, and a protrusion positioned between the first groove and the second groove and defined by the first and second grooves, and a ratio of a width half the width of the protrusion in a circumferential direction of the rotor to a width of the first groove and the second groove in the circumferential direction of the rotor is not smaller than 0.37 and not greater than 6.