Passive magnetic bearings for rotating equipment including induction machines

Abstract

Permanent magnet bearings are incorporated into rotating equipment, such as induction machines, in addition to active magnetic or lubricated primary shaft support bearings. The passive magnetic bearings incorporate permanent magnets that generate directionally oriented magnetic fields of selective intensity. The magnetic field directions are aligned with a desired shaft support bearing preload direction and intensity, for example to exert axial thrust or radial preloads on the support bearings. A plurality of magnetic bearings may be oriented in opposed relationship with neutral or offsetting resultant forces. The passive magnetic force preload may be utilized to offset rotor vertical weight during induction startup or stopping cycles. Passive magnetic force preload may be applied to lubricated bearings to assure their operational stability. The passive magnetic bearings can also absorb radial or axial thrust forces imparted on the rotor shaft during induction machine operation, that may reduce machine operational noise, and energy consumption.

What is claimed is: 
     
         1 . An induction machine apparatus, comprising:
 a machine housing;   a bearing housing coupled to the machine housing;   a stator in the machine housing;   a rotor oriented within the stator, having a rotor shaft rotatively captured in the bearing housing;   a rotor shaft support bearing, selected from the group consisting of a lubricated bearing and an active magnetic bearing, in the bearing housing, rotatively capturing the rotor shaft; and   a permanent magnet bearing in the machine housing, the permanent magnet bearing exerting a directional magnetic force on the rotor shaft that generates a desired intensity and magnitude preload force on the support bearing,   wherein the directional magnetic force preloads the support bearing axially.   
     
     
         2 . The apparatus of  claim 1 , wherein the permanent magnet bearing comprises a sector-shaped permanent magnet, having an inner concave surface in opposed spaced relationship with the rotor shaft, an outer convex surface, axial width, and axial ends; and the magnetic force generated thereby is aligned axially with the rotor shaft centerline. 
     
     
         3 . The apparatus of  claim 2 , wherein the permanent magnet sector shape subtends a circumference of less than 180 degrees. 
     
     
         4 . The apparatus of  claim 2 , wherein the permanent magnet has axial ends defining surface areas, and further comprising electrical steel flanking both axial ends thereof at least partially along the surface area thereof, for orienting the axially directed magnetic force exerted on the shaft. 
     
     
         5 . The apparatus of  claim 4 , wherein the electrical steel comprises a plurality of laminations oriented axially with respect to the permanent magnet. 
     
     
         6 . The apparatus of  claim 2 , further comprising electrical steel affixed to the rotor shaft in opposed spaced relationship with the permanent magnet and at least part of the axial width thereof, for orienting the magnetic force exerted on the shaft. 
     
     
         7 . The apparatus of  claim 1 , further comprising:
 an annular-shaped permanent magnet, having an inner diameter circumference circumscribing an axial axis of the rotor, and respective first and second axial ends;   a flange radially projecting from the rotor in opposed spaced relationship with the first axial end of the permanent magnet; and   a flange constructed of electrical steel having a hub portion concentric with the permanent magnet inner diameter circumference and a rim portion radially projecting from the hub portion that abuts the second end of the permanent magnet.   
     
     
         8 . An induction machine apparatus, comprising:
 a machine housing;   a bearing housing coupled to the machine housing;   a stator in the machine housing;   a rotor oriented within the stator, having a rotor shaft rotatively captured in the bearing housing;   a rotor shaft support bearing, selected from the group consisting of a lubricated bearing and an active magnetic bearing, in the bearing housing, rotatively capturing the rotor shaft;   a permanent magnet bearing in the bearing housing in tandem with the support bearing, having:   a permanent magnet oriented in opposed spaced relationship with the rotor shaft and exerting a directional magnetic force thereon;   electrical steel laminations oriented proximal the permanent magnet for orienting the magnetic force exerted on the shaft;   wherein the permanent magnet bearing directional magnetic force generates a desired intensity and magnitude preload force on the support bearing,   wherein the directional magnetic force preloads the support bearing axially.   
     
     
         9 . The induction machine apparatus of  claim 8 , wherein a plurality of permanent magnet bearings is coupled to the induction machine and are oriented to generate offsetting opposed preload forces on the support bearing. 
     
     
         10 . The induction machine of  claim 8 , wherein the permanent magnet is sector-shaped, having an inner concave surface in opposed spaced relationship with the rotor shaft, an outer convex surface, axial width, and axial ends; and the magnetic force generated thereby is aligned axially with the rotor shaft centerline. 
     
     
         11 . The induction machine of  claim 10 , wherein the permanent magnet sector shape subtends a circumference of less than 180 degrees. 
     
     
         12 . The induction machine of  claim 10 , wherein the permanent magnet has axial ends defining surface areas, and further comprising electrical steel flanking both axial ends thereof at least partially along the surface area thereof, for orienting the axially directed magnetic force exerted on the shaft. 
     
     
         13 . An induction machine comprising:
 a machine housing;   a bearing housing coupled to the machine housing;   a stator in the machine housing;   a rotor oriented within the stator, having a rotor shaft rotatively captured in the bearing housing;   a rotor shaft support bearing, selected from the group consisting of a lubricated bearing and an active magnetic bearing, in the bearing housing, rotatively capturing the rotor shaft; and   a method for preloading bias force on the support bearing, comprising:   
       providing a permanent magnet bearing that generates a directional magnetic force; 
       coupling the permanent magnet bearing to the induction machine proximal the rotor; and 
       orienting the permanent magnet bearing so that its directional magnetic force is exerted on the rotor shaft and generates a desired preload force intensity and direction on the support bearing,
 wherein the directional magnetic force preloads the support bearing axially. 
 
     
     
         14 . The induction machine of  claim 13 , wherein a plurality of permanent magnet bearings is coupled to the induction machine and is oriented to generate offsetting opposed preload forces on the support bearing. 
     
     
         15 . The induction machine of  claim 13 , wherein the permanent magnet bearing comprises a sector-shaped permanent magnet, having an inner concave surface in opposed spaced relationship with the rotor shaft, an outer convex surface, axial width, and axial ends; and the magnetic force generated thereby is aligned axially with the rotor shaft centerline. 
     
     
         16 . The induction machine of  claim 15 , wherein the permanent magnet sector shape subtends a circumference of less than 180 degrees. 
     
     
         17 . The induction machine of  claim 15 , wherein the permanent magnet has axial ends defining surface areas, and further comprising electrical steel flanking both axial ends thereof at least partially along the surface area thereof, for orienting the axially directed magnetic force exerted on the shaft. 
     
     
         18 . The induction machine of  claim 17 , wherein the electrical steel comprises a plurality of laminations oriented axially with respect to the permanent magnet. 
     
     
         19 . The induction machine of  claim 15 , further comprising electrical steel affixed to the rotor shaft in opposed spaced relationship with the permanent magnet and at least part of the axial width thereof, for orienting the magnetic force exerted on the shaft. 
     
     
         20 . The induction machine of  claim 13 , further comprising:
 an annular-shaped permanent magnet, having an inner diameter circumference circumscribing an axial axis of the rotor, and respective first and second axial ends;   a flange radially projecting from the rotor in opposed spaced relationship with the first axial end of the permanent magnet; and   a flange constructed of electrical steel having a hub portion concentric with the permanent magnet inner diameter circumference and a rim portion radially projecting from the hub portion that abuts the second end of the permanent magnet.