An electric motor comprises a stator having a plurality of conductive windings radially spaced about a central axis. The motor includes a rotor located radially inward of the stator and rotationally fixed with respect to a shaft disposed along the central axis. The rotor defines an area in which, upon rotation of the rotor, a low pressure vacuum is created drawing air radially outward, with respect to the rotor, from the area. The rotor also includes an annular plate disposed at a transverse end of the rotor coaxial with the shaft. The annular plate defines at least one hole extending axially through the annular plate and in pneumatic communication with the area. The hole is configured so air is drawn by the low pressure vacuum through the hole to the area.

In a squirrel-cage rotor, the theoretical ideal groove cross section is divided radially into at least two zones, which are displaced relative to each other alternatively in and against the direction of rotation of the rotor, the groove cross section including protuberances that extend into the theoretical ideal groove cross section and bulges that extend from the theoretically ideal groove cross section in a manner that the width of a tooth between the individual grooves remains the same as the theoretical ideal groove cross section, thus preventing the conductor rods from shifting either as they cool after aluminum has been introduced into the grooves or at high rotational rotor speeds.

A permanent magnet rotor comprising a housing defining a central rotor axis, an inner ring secured within the housing and annularly extending around the rotor axis, a plurality of permanent magnets supported within the housing and annularly spaced around the inner ring, and an outer ring secured within the housing, annularly extending around the permanent magnets, and including a plurality of outer ring segments. The rotor further comprises filler material filling spaces between adjacent permanent magnets and adjacent outer ring segments; and a plurality of damper plates located radially outside the filler material, engaging the housing, and engaging and extending between adjacent outer ring segments.

A method of fabricating a dynamo-electric machine rotor is provided. The method includes forming a plurality of laminations, such that a plurality of openings extend through the laminations between an outer peripheral edge and an inner peripheral edge arcuately spaced about the lamination wherein each opening includes an edge with a tongue that extends into the opening, stacking the laminations to form a core wherein adjacent opening are substantially aligned to form a slot in the core and filling the core slots with rotor bar material.