Patent attributes
A permanent-magnet rotating machine includes a rotor having a rotor core carrying on a curved outer surface multiple permanent magnets arranged in two rows along an axial direction. The permanent magnets in one row are skewed from those in the other row in a circumferential direction by a row-to-row skew angle (electrical angle) θe. A stator having a tubular stator core in which the rotor disposed, includes stator coils for producing a rotating magnetic field for rotating the rotor. A lower limit of the row-to-row skew angle θe larger than 30 degrees (electrical angle). A ratio, of cogging torque occurring in the absence of skew to cogging torque occurring when the permanent magnets are skewed, at a row-to-row skew angle of 30 degrees is calculated based on the cogging torque ratio, the row-to-row skew angle θe, and B-H curve properties of the stator core. An upper limit of the row-to-row skew angle θe is not larger than the maximum value at which the cogging torque ratio does not exceed the calculated cogging torque ratio at 30 degrees.
