Methods for tuning magnetic properties of electrical steel cores for electrical devices

Abstract

Methods for tuning properties of electric machines are disclosed. A method for reducing core loss in an electric machine includes punching a plurality of laminations from one or more electrical steel sheets that results in one or more cut edges. The method further includes assembling the laminations into a core such that an outer perimeter surface of the core is defined by the cut edges. The method further includes peening the outer perimeter surface to remove residual stresses.

What is claimed is: 
     
         1 . A method for reducing core loss in an electrical device core comprising:
 punching a plurality of laminations from one or more electrical steel sheets that results in one or more cut edges;   assembling the laminations into the electrical device core such that an outer perimeter surface of the electrical device core is defined by the cut edges; and   peening the outer perimeter surface to remove residual stresses.   
     
     
         2 . The method of  claim 1  further comprising peening an inner perimeter surface that is further defined by the cut edges to remove residual stresses. 
     
     
         3 . The method of  claim 2  wherein the inner perimeter surface defines a plurality of slots and further comprising peening the slots to remove residual stresses. 
     
     
         4 . The method of  claim 1  further comprising peening magnet opening surfaces that are further defined by the cut edges to remove residual stresses. 
     
     
         5 . The method of  claim 1  wherein the peening is performed by one or more of shot peening, wet shot peening, cavitation peening and laser peening. 
     
     
         6 . A method for forming a rotor lamination comprising:
 punching a plurality of openings in the rotor lamination to form magnet openings using a punch having a leading portion configured to punch through the rotor lamination and enter a die beneath the rotor lamination and a tapered portion configured to compress edges defining the magnet openings between the punch and the die when the leading portion penetrates the die to increase plastic deformation at the edges.   
     
     
         7 . The method of  claim 6  wherein the tapered portion is configured to compress predetermined edges. 
     
     
         8 . The method of  claim 6  wherein the tapered portion is configured to compress edges that are adjacent to bridge regions that define a surface between adjacent magnet openings. 
     
     
         9 . The method of  claim 6  wherein the tapered portion is configured to compress edges that are adjacent to an outer perimeter edge of the rotor laminations. 
     
     
         10 . A method for tuning magnetic properties of an electrical device core comprising:
 punching a lamination from electrical steel such that the lamination has one or more cut edges defining an outer perimeter edge of the lamination;   masking the lamination to expose a surface immediately adjacent to and including the outer perimeter edge; and   peening the surface of the lamination.   
     
     
         11 . The method of  claim 10  wherein the cut edges further define a plurality of teeth along an inner perimeter edge of the lamination and further comprising masking the lamination to expose an inner perimeter surface that includes edges of the teeth and the inner perimeter edge; and peening the inner perimeter surface. 
     
     
         12 . The method of  claim 10  further comprising masking an opposite face of the lamination to expose the surface adjacent and including the outer perimeter edge on the opposite face; and peening the surface on the opposite face of the lamination. 
     
     
         13 . The method of  claim 10  wherein the peening is performed by one or more of shot peening, laser peening, cavitation peening and wet shot peening. 
     
     
         14 . The method of  claim 10  wherein the cut edges further define a plurality of openings within an interior of the lamination and the surface exposed during masking includes edges of the openings. 
     
     
         15 . The method of  claim 10  further comprising assembling the laminations into the electrical device core. 
     
     
         16 . The method of  claim 10  wherein the surface exposed during masking includes predetermined regions of the lamination that result in a reduction in magnetic permeability after peening. 
     
     
         17 . A method for decreasing magnetic permeability in an electrical device core comprising:
 punching a lamination for the electrical device core; and   deforming the lamination in a mold to deform the lamination in one or more predefined regions of the lamination at which deformation results in a decrease in magnetic permeability of the electrical device core.   
     
     
         18 . The method of  claim 17  wherein the mold is configured to deform the lamination in the predefined regions in a curved cross-sectional profile. 
     
     
         19 . The method of  claim 17  wherein the mold is configured to deform the lamination by forming an indentation in the predefined regions of the lamination. 
     
     
         20 . The method of  claim 17  wherein the mold is further configured to deform the lamination in the predefined regions by forming a plurality of indentations in a predetermined pattern in the predefined regions.