Permanent magnet motor and electric power steering apparatus

A permanent magnet motor, comprising:

• a rotor including a rotor core fixed on a motor shaft, and permanent magnets fixed on the rotor core;
• and
• a stator including a stator core, whose inner circumferential face opposes to an outer circumferential face of the rotor by means of a magnetic air gap, having a plurality of slots for accommodating armature windings, and a plurality of teeth, the permanent magnet motor characterized in that:
• the armature windings are constituted of a plurality of groups of multi-phase windings;
• the plurality of groups of multi-phase windings is supplied with electric power from individual inverters in every one of respective groups;
• the plurality of teeth each include respective flanges;
• the flanges each have a lateral side portion thereof opposing to a lateral side portion of a flange being provided in the teeth adjacent to each other and protruding in a circumferential direction of the stator core;
• when a height in the lateral side portion of the flanges in a radial direction of the stator core is defined as h, and a length of the magnetic air gap is defined as g, relationship
• 1≤h/g≤2
• is held;
• and also,
• when a circumferential distance between opposing faces of the flanges being adjacent to each other is defined as a, relationship
• a/g≥0.2
• is satisfied, wherein,
• when a circumferential width of the slots corresponding to a portion of the teeth, existing from the flanges on an outer radial side of the stator, where the circumferential width of the stator becomes a smallest is defined as S1, a maximum outer diameter of the rotor core is defined as Rout, and the number of slots is defined as Ns, the width S1 of the slots satisfies a relationship
• 0.5×2π(Rout+g+h)/Ns≤S1≤0.6×2π(Rout+g+h)/Ns, and also
• the circumferential width of the slots gradually increases in accordance with a position on an outer radial side of the stator, and is maximized on a back-portion of the slots or a back-portion's vicinity thereof.