The rotor 120 is formed in a cylindrical shape and is disposed to be rotatable coaxially with the stator 110. The rotor 120 is disposed to be rotatable about the center of the stator 110 at a predetermined gap from the step portions 114 of the teeth 113 of the stator 110. For this purpose, a through hole 121 is formed at the center of the rotor 120, in which a rotation shaft (not illustrated) is disposed.

A plurality of permanent magnets 130 are provided inside the rotor 120 at regular intervals in the circumferential direction. In detail, the plurality of permanent magnets 130 are provided between the through hole 121 and the outer circumferential surface of the rotor 120. The plurality of permanent magnets 130 may be formed in a V shape, which is a magnetic flux concentration type, as illustrated in FIG. 11. For example, two bar-shaped magnets may be arranged in a V-shape.

Further, the plurality of permanent magnets 130 may be formed of ferrite or rare earth material. For example, the plurality of permanent magnets 130 may be formed of neodymium Nd.

The rotor 120 is formed of iron cores and a plurality of magnet insertion holes 123 in which the permanent magnets 130 are disposed are formed at equal intervals in the circumferential direction of the rotor 120. Each of the plurality of magnet insertion holes 123 is formed in a V shape corresponding to the shape of the permanent magnet 130.