Patent ID: 7196445

Claim:
A permanent-magnet rotating machine comprising: a rotor having a rotor core carrying on a curved outer surface multiple permanent magnets which are arranged in two rows along an axial direction so that the permanent magnets in one row are skewed from the permanent magnets in the other row in a circumferential direction, by a row-to-row skew angle θe, expressed in terms of electrical angle; and a stator having a tubular stator core in which the rotor is disposed, the stator core including stator coils for producing a rotating magnetic field which causes the rotor to rotate, wherein the stator core has a relationship between flux density and magnetizing force that is deteriorated due to a manufacturing process as compared to the relationship between flux density and magnetizing force that is unaffected by manufacturing processes, leakage flux occurs inside the stator core along an axial direction due to the row-to-row skew of the rows of magnets, a lower limit of the row-to-row skew angle θe is larger than a theoretical angle θs, expressed in terms of electrical angle by (180 times the number of rotor poles /the smallest number of which the number of stator poles and the number of rotor poles are factors)/(number of permanent magnet rows along the axial direction), a cogging torque ratio, which is the ratio of cogging torque occurring without skew to the cogging torque occurring when the permanent magnets are skewed, at the theoretical angle θs is calculated based on a relationship between the cogging torque ratio and the row-to-row skew angle θe and the relationship between flux density and magnetizing force of the stator core that is deteriorated due to a manufacturing process, and an upper limit of the row-to-row skew angle θe is no larger than a maximum value of the row-to-row skew angle θe at which the cogging torque ratio does not exceed the calculated cogging torque ratio at the theoretical angle θs.