Patent ID: 7550891

Claim:
A permanent-magnet motor comprising: a stator provided with a plurality of teeth; and a rotor having permanent magnets disposed therein; wherein the stator has a plurality of protrusions respectively formed at surfaces of the teeth, at least one protrusion of the plurality of protrusions being opposite to an outer circumferential surface of the rotor, to approximate sinusoidal change in magnetic flux, wherein the rotor has a plurality of grooves respectively formed at an outer circumferential surface thereof, at least one groove of the plurality of grooves being opposite to an inner circumferential surface of the stator, to approximate sinusoidal change in magnetic flux, each stator tooth having a tooth body and a circumferentially-extended end portion that is wider than the tooth body, wherein the plurality of protrusions are respectively formed in a shape of a plurality of steps at the circumferentially extended end of each tooth opposite to the outer circumferential surface of the rotor, at least one step of the plurality of steps is formed at a middle part of the circumferentially extended end of a tooth of the plurality of teeth of the stator, and an innermost step of the plurality of steps extends to a width that is greater than or equal to a width of the tooth body and is greater than a distance between two stator teeth.