Patent ID: 7605514

Claim:
An electric machine comprising: an armature; and a field pole unit rotating relative to said armature along a magnetic gap between said armature and said field pole unit, said armature including: an armature core having a plurality of teeth extending toward the magnetic gap at a uniform interval along a rotational direction of said armature relative to said field pole unit, and a plurality of armature coils concentratedly wound around respective teeth for the flow of phase currents from a three-phase AC power supply, wherein said field pole unit has a fixed number of magnetic poles arranged along the rotational direction, said plurality of teeth include at least one tooth around which at least two armature coils for the flow of different phase currents are wound to reduce harmonic components of magnetomotive forces produced by the armature coils when said electric machine is operated, the reduced harmonic components being of a lower order than a component synchronized with relative moving speed of said armature and said field pole unit, the number of poles P of said field pole unit and the number of teeth Q of said armature are selected from one of the combinations consisting of P=5n and Q=6n, and P=7n and Q=6n, respectively, where n is an even number, and said armature coils are wound around successive teeth with phase relationships and winding polarities arranged in the repeating order of U+/U+, U−/V+, V−/V−, W−/V+, W+/W+, W−/U+, U−/U−, U+/V−, V+/V+, W+/V−, W−/W−, and W+/U−, where U, V, and W represent phases of individual armature coils and + and − denote winding polarities of said armature coils.