US Patent 7233090 Electric machine, in particular brushless synchronous motor

An electrical machine, in particular a brushless synchronous motor has a stator (14) and a rotor (12) with salient poles (18) disposed distributed over its circumference, each of which poles has an enclosed permanent magnet (11) and a pole shoe (19) that extends radially outward from the permanent magnet and defines an air gap (13) between the stator (14) and rotor (12). In order to achieve a low cogging torque and a low torque undulation, the pole shoes (19) are embodied as magnetically anisotropic, with a preferred direction of the greater magnetic conductivity extending parallel to the radial salient pole axis.