System and method for smoothing a salient rotor in electrical machines

Abstract

An electrical machine exhibiting reduced friction and windage losses is disclosed. The electrical machine includes a stator and a rotor assembly configured to rotate relative to the stator, wherein the rotor assembly comprises a rotor core including a plurality of salient rotor poles that are spaced apart from one another around an inner hub such that an interpolar gap is formed between each adjacent pair of salient rotor poles, with an opening being defined by the rotor core in each interpolar gap. Electrically non-conductive and non-magnetic inserts are positioned in the gaps formed between the salient rotor poles, with each of the inserts including a mating feature formed an axially inner edge thereof that is configured to mate with a respective opening being defined by the rotor core, so as to secure the insert to the rotor core against centrifugal force experienced during rotation of the rotor assembly.

What is claimed is: 
     
         1 . An electrical machine comprising:
 a stator;   a rotor assembly disposed within the stator and configured to rotate relative to the stator, wherein the rotor assembly comprises:
 a rotor core constructed of a stack of laminations, the rotor core comprising a plurality of salient rotor poles that are spaced apart from one another around an inner hub such that an interpolar gap is formed between each adjacent pair of salient rotor poles; and 
 a plurality of inserts positioned in the gaps formed between the plurality of salient rotor poles, the inserts each formed as a single piece extending axially through the stack of laminations of the rotor core and each being entirely formed of nonconductive and non-magnetic material. 
   
     
     
         2 . The electrical machine of  claim 1  wherein the inserts each comprise a mating feature forming an axially inner edge thereof configured to mate with a corresponding opening in each interpolar gap defined by the rotor core. 
     
     
         3 . The electrical machine of  claim 2  wherein the mating feature comprises a dovetail feature configured to mate with an opening formed in the inner hub of the rotor core. 
     
     
         4 . The electrical machine of  claim 1  wherein the rotor assembly further comprises a pair of non-conductive and non-magnetic end plates positioned on axially opposing ends of the rotor core. 
     
     
         5 . The electrical machine of  claim 4  wherein opposing ends of each insert comprise an additional mating feature formed on each end thereof configured to mate with a corresponding opening on each end plate. 
     
     
         6 . The electrical machine of  claim 1  wherein the plurality of salient rotor poles comprises a plurality of rotor teeth. 
     
     
         7 . The electrical machine of  claim 1  wherein each of the plurality of inserts comprises a T-shaped insert comprising:
 a lengthwise member extending in a radial direction; and 
 a crosswise member extending normally between two adjacent rotor poles. 
 
     
     
         8 . The electrical machine of  claim 7  wherein the crosswise member forms a smooth outer surface on the rotor in combination with a pair of adjacent rotor poles. 
     
     
         9 . The electrical machine of  claim 7  wherein each of the plurality of rotor poles comprises a pair of flange-like protrusions formed at a radially outermost portion thereof, wherein the crosswise member includes a shoulder on each end thereof configured to mate with the pair of flange-like protrusions. 
     
     
         10 . The electrical machine of  claim 7  wherein each of the plurality of rotor poles comprises a pair of axially-extending notches formed in proximity to the radially outermost portion thereof, wherein the crosswise member includes a shoulder on each end thereof configured to mate with the pair of axially-extending notches. 
     
     
         11 . A rotor assembly for an electrical machine comprising:
 a rotor core constructed of a stack of laminations, the rotor core comprising a plurality of salient rotor poles that are spaced apart from one another around an inner hub such that an interpolar gap is formed between each adjacent pair of salient rotor poles; and   a plurality of inserts positioned in the gaps formed between the plurality of salient rotor poles, the inserts each formed as a single piece extending axially through the stack of laminations of the rotor core and each being entirely formed of nonconductive and non-magnetic material.   
     
     
         12 . The rotor assembly of  claim 11  wherein the rotor assembly further comprises a pair of non-conductive and non-magnetic end plates positioned on axially opposing ends of the rotor core. 
     
     
         13 . The rotor assembly of  claim 12  wherein opposing ends of each insert comprise an additional mating feature formed on each end thereof configured to mate with a corresponding opening on each end plate. 
     
     
         14 . The rotor assembly of  claim 11  wherein each of the plurality of inserts comprises a T-shaped insert comprising:
 a lengthwise member extending in a radial direction; and 
 a crosswise member extending normally between two adjacent rotor poles. 
 
     
     
         15 . The rotor assembly of  claim 14  wherein the crosswise member forms a smooth outer surface on the rotor in combination with a pair of adjacent rotor poles. 
     
     
         16 . The rotor assembly of  claim 14  wherein each of the plurality of rotor poles comprises a pair of flange-like protrusions formed at a radially outermost portion thereof, wherein the crosswise member includes a shoulder on each end thereof configured to mate with the pair of flange-like protrusions. 
     
     
         17 . The rotor assembly of  claim 14  wherein each of the plurality of rotor poles comprises a pair of axially-extending notches formed in proximity to the radially outermost portion thereof, wherein the crosswise member includes a shoulder on each end thereof configured to mate with the pair of axially-extending notches. 
     
     
         18 . An electrical machine comprising:
 a stator;   a rotor assembly disposed within the stator and configured to rotate relative to the stator, wherein the rotor assembly comprises:
 a rotor core comprising a plurality of salient rotor poles that are spaced apart from one another around an inner hub such that an interpolar gap is formed between each adjacent pair of salient rotor poles; and 
 a plurality of inserts positioned in the gaps formed between the plurality of salient rotor poles, the inserts each formed as a single piece extending axially through the rotor core and each being entirely formed of nonconductive and non-magnetic material. 
   
     
     
         19 . The electrical machine of  claim 19  wherein the rotor core is formed as a single piece of material. 
     
     
         20 . The electrical machine of  claim 19  wherein the rotor assembly further comprises a pair of non-conductive and non-magnetic end plates positioned on axially opposing ends of the rotor core. 
     
     
         21 . The electrical machine of  claim 20  wherein opposing ends of each insert comprise an additional mating feature formed on each end thereof configured to mate with a corresponding opening on each end plate.