Electric motor having improved rotor assembly, and method by which the rotor assembly is made

Abstract

A rotor assembly for an induction motor has cast end rings located at each axial end of a magnetically permeable core. The end rings electrically connect conductor bars extending through conductor channels in the core to provide a squirrel cage arrangement. The end rings are configured to define an annular peak along which a plurality of mounting sprews are located. Preferably, the mounting sprews are positioned between adjacent pairs of radial fan blades. The annular peak may be formed by a tapered structure which advantageously provides a narrower end ring width near the rotor's outer diameter surface. The reduced width at this location presents a higher resistance in the lock rotor condition, thus yielding an improved lock rotor specification in many cases. Due to the "deep bar effect," current will flow through the thicker portion of the end rings at higher operating speeds (i.e., lower slip frequency). As a result, a lower resistance will be realized as the motor is brought up to speed.

Dependencies are inferred from the claim text.