WE CLAIM:
1. A permanent magnet motor comprising:
a rotor (11) including a rotor iron core (12) and a plurality of permanent magnets (13) provided to the rotor iron core (12); and
a stator (21) including a stator iron core (22) having a plurality of teeth (24), and two sets of three-phase armature windings (30) provided in a plurality of slots (27) formed in the stator iron core (22), a first armature winding (30-1) being supplied with current from a first inverter (102-1) and a second armature winding (30-2) being supplied with current from a second inverter (102-2), wherein
in the case where the two sets of three-phase armature windings (30) are defined such that the first armature winding corresponds to U1 phase, V1 phase, and W1 phase and the second armature winding (30-2) corresponds to U2 phase, V2 phase, and W2 phase, the U1 phase, the V1 phase, and the W1 phase of the first armature winding are shifted by an electric angle of 20° to 40° from the U2 phase, the V2 phase, and the W2 phase of the second armature winding (30-2) upon driving,
characterized in that
the U1 phase of the first armature winding is provided in both slots of any one pair of adjacent slots of the plurality of slots (27), or at least one of the U1 phase of the first armature winding and the U2 phase of the second armature winding (30-2) is provided in one slot of any one pair of adjacent slots of the plurality of slots (27), and
a slot opening width Ws of the stator iron core (22) is set so as to satisfy Ws/(2πRs/Ns)g0.15, where Rs is an inner radius of the stator iron core (22) and Ns is a slot number of the stator iron core (22), and
a core back thickness Wc of the stator core (22) is set to be in range of 0.18 < Wc/(2πRs/M)< 0.50, wherein M is a pole number of the rotor (11).
2. The permanent magnet motor according to claim 1, wherein
the winding for U1 phase of the first armature winding is wound on one tooth of any one pair of adjacent teeth of the plurality of teeth (24), and the winding for U2 phase of the second armature winding (30-2) is wound on the other tooth,

the winding for V1 phase of the first armature winding is wound on one tooth of another pair of adjacent teeth of the plurality of teeth (24), and the winding for V2 phase of the second armature winding (30-2) is wound on the other tooth, and
the winding for W1 phase of the first armature winding is wound on one tooth of still another pair of adjacent teeth of the plurality of teeth (24), and the winding for W2 phase of the second armature winding (30-2) is wound on the other tooth.
3. The permanent magnet motor according to claim 1, wherein ends of adjacent teeth (24) of the stator iron core (22) are connected with each other.
4. The permanent magnet motor according to claim 1, wherein a greatest common divisor P between M and Ns is three or greater, where M is the pole number of the rotor (11) and Ns is the slot number of the stator iron core (22).
5. The permanent magnet motor according to claim 1, wherein M=18n ± 4n and Ns=18n (n is an integer) are satisfied, where M is the pole number of the rotor (11) and Ns is the slot number of the stator iron core (22).
6. The permanent magnet motor according to claim 1, wherein M=12n ± 2n and Ns=12n (n is an integer) are satisfied, where M is the pole number of the rotor (11) and Ns is the slot number of the stator iron core (22).
7. The permanent magnet motor according to claim 1, wherein the slot opening width Ws is smaller than a wire diameter of the armature windings (30).
8. The permanent magnet motor according to claim 1, wherein the permanent magnets (13) are embedded in the rotor iron core (12), and the length in a radius direction of each permanent magnet (13) is longer than the length in a circumferential direction.
9. The permanent magnet motor according to claim 1, wherein
the permanent magnets (13) have a cross-sectional shape of rectangle, and the length in a radius direction of each permanent magnet (13) is longer than the length in a circumferential direction,
the magnetization directions of the permanent magnets (13) are set such that surfaces facing to each other of the adjacent permanent magnets (13) have the same pole,
the rotor iron core (12) is interposed between the adjacent permanent magnets (13) and has a curved surface portion (31) on a surface thereof facing to the stator side, the

shape of the curved surface portion (31) being formed to be such a convex curved surface that a gap length from the stator (21) is shortened toward a midpoint between the adjacent permanent magnets (13), and
a non-magnetic portion is provided in contact with an end surface of each permanent magnet (13) on an inner circumferential side.
10. The permanent magnet motor according to claim 1, wherein the permanent magnets (13) of the rotor (11) are arranged in the circumferential direction, the number of the permanent magnets (13) being M/2, where M is the pole number of the stator (21).
11. The permanent magnet motor according to claim 10, wherein
the permanent magnets (13) are embedded in the rotor iron core (12), and the length in a radius direction of each permanent magnet (13) is longer than the length in a circumferential direction,
a non-magnetic portion (32) is provided on the inner circumferential side of each permanent magnet (13), and
a non-magnetic portion (33) is provided between the adjacent permanent magnets (13).
12. The permanent magnet motor according to claim 1, wherein the armature windings (30) of the stator (21) are wound in a distributed manner, and the slot number for each pole for each phase is an even number equal to or greater than 2.
13. The permanent magnet motor according to any one of claims 1 to 12, the permanent magnet motor being provided in parallel to a movement direction of a rack shaft of an electric power steering apparatus.