Patent ID: 7239060

Claim:
A direct current (DC) motor comprising: a stator, including a number of poles 2P and a stator core; a concentrated-winding rotor, including: a rotor core made of a ferromagnetic material and separated from the stator core by an airgap, a number of rotor slots S, and a number of rotor teeth S, wherein S/2 of the rotor teeth have different geometrical dimensions from other remaining ones of the rotor teeth, and wherein, for each tooth of the S/2 of the rotor teeth, a plurality of non-overlapping coils of insulated wire is wound around the tooth; and a commutator with a number of segments Z, wherein the number of stator poles 2P, the number of rotor slots S, and the number of commutator segments Z to satisfy the following conditions: P is an integer and 1 < P < 10 S = 2P + 2A A is an integer and 1 < A < P Z = k*LCM(S/2, 2P) ± n k is an integer greater than 0 LCM is the Least Common Multiple of S/2 and 2P n is equal to 0 or k or Z = LCM(S/2, 2P)/2.