The utility model discloses a motor. The number of bulged poles of a
stator is twelve, and the number of
magnetic poles formed on the
peripheral surface of a rotor is ten. The motor not only can form an effective
magnetic circuit, but also can reduce the
cogging torque. In the motor, the
stator (3) disposed at the radial
peripheral side of the rotor (2) comprises a
stator core (13) which is provided with twelve bulged poles (13a) bulging radially inwards. The rotor (2) comprises a plurality of permanent magnets (8) which are arranged in the
peripheral direction in an adjacent manner, and are arranged opposite to
tail end faces (13e) of the bulged poles (13a), wherein there are gaps between the permanent magnets (8) and the
tail end faces (13e) of the bulged poles (13a). The number of the
magnetic poles on the peripheral surface of the rotor (2) is ten. The
tail end faces (13e) of the bulged poles (13a) form a concave curved surface through smooth connection surfaces, and surfaces (8b), opposite to the tail end faces (13e) of the bulged poles (13a), of the permanent magnets (8), form a convex curved surface. In the motor, the ratio R1 / R2 of the
radius R1 of an imaginary circle contacting with a part of surfaces (8b) of the permanent magnets (8) to the curvature
radius R2 of each of the surfaces (8b) of the permanent magnets (8) is from 0.4 to 0.55.