Rotor design for an electric motor having brazed structure for connecting rotor bars

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 comprising:
 a rotor shaft;   a plurality of laminated discs formed into a stack of laminated discs, wherein the plurality of laminated discs include a plurality of slots, wherein the plurality of slots of the plurality of laminated discs are co-aligned within the stack of laminated discs, and wherein the stack of laminated discs is mounted to the rotor shaft;   a plurality of rotor bars passing through the plurality of slots of the stack of laminated discs, wherein first end portions of the plurality of rotor bars extend out and away from a first end surface of the stack of laminated discs, and wherein second end portions of the plurality of rotor bars extend out and away from a second end surface of the stack of laminated discs;   a plurality of first separate and independent slugs, wherein respective first separate and independent slugs of the plurality of first separate and independent slugs, are interposed between respective first end portions of respective pairs of rotor bars of the plurality of rotor bars; and   a plurality of second separate and independent slugs, wherein respective second separate and independent slugs of the plurality of second separate and independent slugs, are interposed between respective second end portions of respective pairs of rotor bars of the plurality of rotor bars.   
     
     
         2 . The rotor assembly of  claim 1 , further comprising:
 a first containment ring positioned over the first end portions of the plurality of rotor bars and over the plurality of first separate and independent slugs; and   a second containment ring positioned over the second end portions of the plurality of rotor bars and over the plurality of second separate and independent slugs.   
     
     
         3 . The rotor assembly of  claim 2 , wherein the first end portions of the plurality of rotor bars and the plurality of first separate and independent slugs have been machined, and wherein the second end portions of the plurality of rotor bars and the plurality of second separate and independent slugs have been machined. 
     
     
         4 . The rotor assembly of  claim 1 , wherein the plurality of first separate and independent slugs and the plurality of second separate and independent slugs are coated in silver. 
     
     
         5 . The rotor assembly of  claim 4 , wherein the plurality of first separate and independent slugs and the plurality of second separate and independent slugs are made of copper. 
     
     
         6 . The rotor assembly of  claim 4 , wherein the plurality of first separate and independent slugs are brazed to respective first end portions of the plurality of rotor bars and the plurality of second separate and independent slugs are brazed to the plurality of rotor bars. 
     
     
         7 . The rotor assembly of  claim 1 , wherein a lower portion of the plurality of first separate and independent slugs, and the plurality of second separate and independent slugs, is chamfered. 
     
     
         8 . The rotor assembly of  claim 1 , wherein an upper edge of the plurality of first separate and independent slugs, and the plurality of second separate and independent slugs, includes a marking. 
     
     
         9 . The rotor assembly of  claim 8 , wherein the marking includes a groove. 
     
     
         10 . The rotor assembly of  claim 1 , wherein the plurality of first separate and independent slugs extend beyond the first end portions in a first axial direction away from the first end surface of the stack of laminated discs and wherein the plurality of second separate and independent slugs extend beyond the second end portions in a second axial direction away from the second end surface of the stack of laminated discs. 
     
     
         11 . A rotor assembly comprising:
 a rotor shaft;   a plurality of laminated discs formed into a stack of laminated discs, wherein the plurality of laminated discs include a plurality of slots, wherein the plurality of slots of the plurality of laminated discs are co-aligned within the stack of laminated discs, and wherein the stack of laminated discs is mounted to the rotor shaft;   a plurality of rotor bars passing through the plurality of slots of the stack of laminated discs, wherein first end portions of the plurality of rotor bars extend out and away from a first end surface of the stack of laminated discs, and wherein second end portions of the plurality of rotor bars extend out and away from a second end surface of the stack of laminated discs;   a plurality of first separate and independent slugs, wherein respective first separate and independent slugs of the plurality of first separate and independent slugs, are interposed between respective first end portions of respective pairs of rotor bars of the plurality of rotor bars; and   a plurality of second separate and independent slugs, wherein respective second separate and independent slugs of the plurality of second separate and independent slugs, are interposed between respective second end portions of respective pairs of rotor bars of the plurality of rotor bars;   wherein less than all of the first end portions of the plurality of rotor bars and the plurality of first separate and independent slugs have been machined to define a first machined portion; and   wherein less than all of the second end portions of the plurality of rotor bars and the plurality of second separate and independent slugs have been machined to define a second machined portion.   
     
     
         12 . The rotor assembly of  claim 11 , further comprising:
 a first containment ring positioned over the first end portions of the plurality of rotor bars and over the plurality of first separate and independent slugs; and   a second containment ring positioned over the second end portions of the plurality of rotor bars and over the plurality of second separate and independent slugs.   
     
     
         13 . The rotor assembly of  claim 12 , wherein the first containment ring is positioned over the first machined portion of the plurality of rotor bars and the plurality of first separate and independent slugs, and wherein the second containment ring is positioned over the second machined portion of the plurality of rotor bars and the plurality of second separate and independent slugs that have been machined. 
     
     
         14 . The rotor assembly of  claim 11 , wherein the plurality of first separate and independent slugs and the plurality of second separate and independent slugs are coated in silver. 
     
     
         15 . The rotor assembly of  claim 14 , wherein the plurality of first separate and independent slugs and the plurality of second separate and independent slugs are made of copper. 
     
     
         16 . The rotor assembly of  claim 14 , wherein the plurality of first separate and independent slugs are brazed to respective first end portions of the plurality of rotor bars and the plurality of second separate and independent slugs are brazed to the plurality of rotor bars. 
     
     
         17 . The rotor assembly of  claim 11 , wherein a lower portion of the plurality of first separate and independent slugs, and the plurality of second separate and independent slugs, is chamfered. 
     
     
         18 . The rotor assembly of  claim 11 , wherein an upper edge of the plurality of first separate and independent slugs, and the plurality of second separate and independent slugs, includes a marking. 
     
     
         19 . The rotor assembly of  claim 18 , wherein the marking includes a groove. 
     
     
         20 . The rotor assembly of  claim 11 , wherein the plurality of first separate and independent slugs extend beyond the first end portions in a first axial direction away from the first end surface of the stack of laminated discs and wherein the plurality of second separate and independent slugs extend beyond the second end portions in a second axial direction away from the second end surface of the stack of laminated discs.