Patent ID: 7342338

Claim:
A permanent magnet electric motor comprising: a rotor having an upper stage permanent magnet and a lower stage permanent magnet provided in an axial direction on an outer circumferential face of a rotor iron core, and said lower stage permanent magnet shifted from said upper stage permanent magnet by a first stage skew angle θr with respect to a center line passing through said upper and lower stage permanent magnets, to decrease a first frequency component of a cogging torque in a circumferential direction of said rotor iron core; a stator iron core of cylindrical shape provided with a stator winding for producing a rotating magnetic field causing said rotor to be rotated; and said stator iron core divided into plural blocks in the axial direction, and shifted by a second stage skew angle θs to decrease a second frequency component of said cogging torque in a circumferential direction of said stator iron core, wherein, when the axial length of said stator iron core is Lc (m), and a theoretical angle of said first stage skew angle θr(°) is an electrical angle θt(°), the following expression is satisfied, θ t =(360°/least common multiple of the number of stator magnetic poles and the number of rotor magnetic poles)/2 (1) θ t<θr <(700×10 −3 /Lc+θt ) (2).