Patent ID: 8601671

Claim:
A method of manufacturing a permanent-magnet synchronous motor, comprising: assembling a rotor having permanent magnets with 2×p poles (where p is a natural number) and inserting the rotor into a toroidal stator that has Z (where Z is a natural number) slots and Z teeth, and on which a coil is arranged; rotating the rotor with no electrical current flowing through the coil and measuring cogging torque of the rotor as a function of angle of rotation of the rotor relative to the stator; identifying angular locations on an outer periphery of the stator where the cogging torque measured has an extreme value; and placing the stator inside a frame and inserting pressurizing parts, which apply pressure to the outer periphery of the stator toward the rotor, between the frame and the stator, at N locations, wherein N is any one of the positive values calculated from N=p, N=±2×p−Z×i1 (where i1 is an integer and at least 0), and N=Z×i1±2×p, the pressurizing parts located at the N locations locally change relative permeability of the stator and reduce the cogging torque measured, and at least one of the pressurizing parts is located at a position where the cogging torque measured is zero or substantially zero.