The present invention provides a rotor assembly comprising: a rotor including a core body, and a plurality of protrusion parts coupled to the core body so as to be detachable therefrom; and an insulator including a body encompassing the protrusion parts, and blades formed to protrude from the upper and lower surfaces of the body, thereby providing an advantageous effect of reducing the number of parts to be manufactured such that manufacturing costs and manufacturing processes can be reduced.