Abstract: A rotor assembly includes a rotor core which has a central portion and a circumferential portion, wherein a shaft hole is formed at the central portion, and a plurality of conductors are arranged along the circumferential portion; a multiplicity of permanent magnets provided at a portion of the rotor core around the shaft hole; and at least one first ripple-reduction conductor formed at a polar switchover region of the rotor core, the polar switchover region being positioned between two opposite poles of two adjacent permanent magnets, so that a polar switchover of an induction voltage induced in the rotor core is alleviated to reduce a torque ripple phenomenon.

Abstract: A motor includes, a stator made of compressed soft magnetic powder, with a plurality of bolt holes formed around a circumferential outer surface of an end of the stator; a cover fitted over the end of the stator, with a plurality of coupling position adjustment parts provided around an end of the cover, the coupling position adjustment parts each comprising a plurality of through holes arranged in a direction in which the cover is fitted over the stator; and a plurality of coupling bolts, each of the plurality of coupling bolts being tightened into each of the bolt holes of the stator through the selected through hole of the associated coupling position adjustment part of the cover such that a position at which the cover is coupled to the stator is adjustable.