A rotor including a cylindrical iron core having a through hole for receiving a rotational shaft, and a squirrel-cage conductive body including a plurality of conductive bars and a pair of annular conductive end rings provided at both ends of the plurality of conductive bars is provided. The transistor has an active region protruding from a predetermined region of a substrate and a groove formed in the active region. A method of retrofitting an enclosed track rail to a material handling system having an open-roller track is also provide.