Stator for permanent magnet brushless electric motor rotor - uses ring stator winding perpendicular to rotor axis with U=shaped pole pieces in form of segment of annulus

摘要

The stator has a winding (10) in the form of a ring coaxial with the rotor axis and in a plane perpendicular to the rotor axis. The ferromagnetic pole pieces (1-8) are U-shaped when viewed from a direction perpendicular to the rotor axis, and straddle the stator winding. Each pole piece has the shape of a segment of an annulus (16) when viewed along the direction of the rotor axis. Alternate segments (1,2) have the bridge (14,12) of the U-shaped pole piece outside then inside the stator winding (10). The rotor has two discs mounted perpendicular to its axis and carrying, at the same pitch as the stator poles, permanent magnets with alternate polarity. The ferromagnetic discs face the ends (16) of the stator poles so the magnetic path through the stator poles is parallel to the rotor axis. This stator construction allows closer pole placement with less leakage flux and consequent reduction in rotor size for a given rotor torque.