Rotor Design for an Electric Motor

Abstract

A rotor assembly is provided in which a solid rotor ring is formed at either end of a stack of laminated discs, the solid rotor rings yielding improved electrical and mechanical characteristics in a low weight assembly. The solid rotor rings are fabricated by brazing slugs between the end portions of the rotor bars, the braze joints contacting a large percentage (at least 90%) of the rotor bar end portions.

What is claimed is: 
     
         1 . A rotor assembly for an electric motor, comprising:
 a rotor shaft;   a plurality of laminated discs formed into a stack of laminated discs, wherein each of said plurality of laminated discs includes a plurality of slots, wherein said plurality of slots of each of said plurality of laminated discs are co-aligned within said stack of laminated discs, and wherein said stack of laminated discs is mounted to said rotor shaft;   a plurality of rotor bars passing through said plurality of slots of said stack of laminated discs, wherein a first end portion of each of said plurality of rotor bars extends out and away from a first end surface of said stack of laminated discs, and wherein a second end portion of each of said plurality of rotor bars extends out and away from a second end surface of said stack of laminated disc;   a first plurality of slugs, wherein each of said first plurality of slugs is interposed between said first end portions of a corresponding pair of said plurality of rotor bars, and wherein each of said first plurality of slugs is joined to said first end portions of said corresponding pair of said plurality of rotor bars via a first pair of braze joints, and wherein each of said first pair of braze joints is brazed to at least 90% of said first end portions of said corresponding pair of said plurality of rotor bars; and   a second plurality of slugs, wherein each of said second plurality of slugs is interposed between said second end portions of a corresponding pair of said plurality of rotor bars, and wherein each of said second plurality of slugs is joined to said second end portions of said corresponding pair of said plurality of rotor bars via a second pair of braze joints, and wherein each of said second pair of braze joints is brazed to at least 90% of said second end portions of said corresponding pair of said plurality of rotor bars.   
     
     
         2 . The rotor assembly of  claim 1 , further comprising:
 a first containment ring positioned around a section of said first end portions of said plurality of rotor bars and over a section of said first plurality of slugs brazed to said first end portions of said plurality of rotor bars; and   a second containment ring positioned around a section of said second end portions of said plurality of rotor bars and over a section of said second plurality of slugs brazed to said second end portions of said plurality of rotor bars.   
     
     
         3 . The rotor assembly of  claim 2 , wherein said section of said first end portions of said plurality of rotor bars and said section of said first plurality of slugs brazed to said first end portions of said plurality of rotor bars is machined prior to positioning said first containment ring, and wherein said section of said second end portions of said plurality of rotor bars and said section of said second plurality of slugs brazed to said second end portions of said plurality of rotor bars is machined prior to positioning said second containment ring. 
     
     
         4 . The rotor assembly of  claim 1 , wherein said plurality of rotor bars are formed from copper, wherein said first plurality of slugs are formed from copper and subsequently coated with silver; and wherein said second plurality of slugs are formed from copper and subsequently coated with silver. 
     
     
         5 . The rotor assembly of  claim 1 , wherein each of said first pair of braze joints is brazed to at least 95% of said first end portions of said corresponding pair of said plurality of rotor bars, and wherein each of said second pair of braze joints is brazed to at least 95% of said second end portions of said corresponding pair of said plurality of rotor bars. 
     
     
         6 . The rotor assembly of  claim 1 , wherein each of said first pair of braze joints is brazed to at least 99% of said first end portions of said corresponding pair of said plurality of rotor bars, and wherein each of said second pair of braze joints is brazed to at least 99% of said second end portions of said corresponding pair of said plurality of rotor bars.