US Patent 7928622 Brushless motor with skewed rotor segments

In a brushless motor including a rotor having 2n magnetic poles and a stator having 3n slots, the magnetic poles of the rotor are composed of segment magnets arranged in three columns extending in an axial direction. The magnets of each column are displaced from the magnet of either adjacent column in a circumferential direction, forming a 3-stage step-skew structure. The segment magnets have a skew angle θskew ranging from 36° to 57° in terms of electrical angle.