Patent ID: 8587174

Claim:
A rotor assembly for an electric device, the rotor assembly comprising: a plurality of electric steel sheets each defining a plurality of slots disposed angularly about and equidistant from a central axis, wherein the plurality of electric steel sheets are disposed adjacent each other to define a laminated stack having a first end surface and a second end surface spaced from the first end surface along the central axis, with the plurality of slots aligned to define a plurality of longitudinal grooves in the laminated stack; a plurality of conductor bars, with one of the plurality of conductor bars disposed within each of the plurality of longitudinal grooves, wherein each of the plurality of conductor bars includes a first end extending axially beyond the first end surface of the laminated stack along the central axis; and a first end ring disposed against and abutting the first end surface and at least partially surrounding and electrically connecting the first end of each of the plurality of conductor bars; wherein the first end of each of the plurality of conductor bars includes a textured surface having micro-sized surface irregularities mechanically interlocking with the first end ring; wherein the micro-sized surface irregularities of the textured surface include a minimum radius R defined by the equation: R = 2 ⁢ γ P wherein γ is the surface tension of a liquid material used to cast the first end ring and/or the second end ring, and P is the pressure applied to the liquid material during solidification.