Induction motor with a circumferentially slitted squirrel cage rotor

Abstract

A rotor for an induction motor is provide. The rotor includes a core built with stacks of a plurality of steel sheets and includes a plurality of rotor slots that are radially arranged. The rotor further includes a plurality of conductor bars contained in the plurality of rotor slots, respectively, and end-rings attached to both longitudinal ends of each of the plurality of conductor bars. The rotor further includes at least one slit formed inward from an outer periphery of the rotor along a perimeter of the rotor, wherein the slit has a depth deep enough to form a groove portion in at least some region of each of the plurality of conductor bars.

What is claimed is: 
     
         1 . A rotor for an induction motor, the rotor comprising:
 a core built with stacks of a plurality of steel sheets and comprising a plurality of rotor slots that are radially arranged;   a plurality of conductor bars contained in the plurality of rotor slots, respectively; and   end-rings attached to both longitudinal ends of each of the plurality of conductor bars,   wherein the rotor further comprises at least one slit formed inward from an outer periphery of the rotor along a perimeter of the rotor, wherein the slit has a depth deep enough to form a groove portion in at least some region of each of the plurality of conductor bars.   
     
     
         2 . The rotor of  claim 1 , wherein the slit is a circular slit disposed in a plane perpendicular to an axis of rotation of the rotor, and a plurality of circular slits are disposed in a lengthwise direction of the rotor. 
     
     
         3 . The rotor of  claim 1 , wherein the slit is a helical slit which is formed along a helical path around an axis of rotation of the rotor. 
     
     
         4 . The rotor of  claim 3 , wherein the helical slit is formed on the outer periphery of the core. 
     
     
         5 . The rotor of  claim 4 , wherein the helical slit is formed so that both ends thereof are positioned between opposite sides of the rotor, and depth and/or cross-sectional area of the helical slit is gradually reduced. 
     
     
         6 . The rotor of  claim 4 , wherein the helical slit comprises a slit opening formed through opposite sides of the rotor past the end-rings. 
     
     
         7 . The rotor of  claim 6 , wherein the slit opening comprises:
 a first edge where a direction of helix of the helical slit forms an acute angle with a side of the rotor;   a second edge where the direction of helix of the helical slit forms an obtuse angle with the side of the rotor; and   a third edge where a bottom surface of the helical slit and the side of the rotor meet,   wherein the slit opening further comprises a protrusion protruding from a side portion of the rotor contiguous to the first edge.   
     
     
         8 . The rotor of  claim 7 , wherein the side portion of the rotor contiguous to the first edge comprises a threaded hole, and the protrusion is fastened into the threaded hole. 
     
     
         9 . The rotor of  claim 8 , wherein the protrusion is a head of a bolt screwed into the threaded hole.