Apparatus and Method for Magnetically Unloading a Rotor Bearing

Abstract

An apparatus and method for unloading a rotor bearing is described. The apparatus includes an electromagnet for levitating the rotor. In one embodiment, a sensor of the magnetic field near the electromagnet is used to control the current to levitate the rotor. In another embodiment, a method is provided that includes rotating the rotor, increasing the current to levitate the rotor and decrease the gap between electromagnet and rotor, and then reducing the current to levitate the rotor with a minimal amount of electric power to the electromagnet.

1 - 11 . (canceled) 
     
     
         12 . A flywheel device comprising:
 a housing;   a rotor disposed within the housing;   a lower bearing assembly comprising lower bearings and an upper bearing assembly comprising upper bearings disposed between the rotor and a plate; and   an off-loading electromagnet configured to provide a vertical off-loading force that lifts the rotor against the upper bearings in a vertical direction and off of the lower bearings.   
     
     
         13 . The flywheel device of  claim 12 , further comprising:
 a force sensor configured to measure a load applied to at least one of the upper bearings or the lower bearings; and   a control system configured to adjust a field of the off-loading electromagnet based on the measured load.   
     
     
         14 . The flywheel device of  claim 13 , wherein the controller is configured to compare the measured load to predetermined load limits. 
     
     
         15 . The flywheel device of  claim 13 , wherein the load applied to at least one of the upper bearings or the lower bearings comprises a vertical force that is applied against the at least one of the upper bearings or the lower bearings. 
     
     
         16 . The flywheel device of  claim 12 , further comprising a spring configured to exert a minimum required force in the vertical direction on at least one of the lower bearings or the upper bearings via the rotor. 
     
     
         17 . The flywheel device of  claim 12 , wherein the housing is hermetically sealed and provides a vacuum envelope within which the rotor is displaced. 
     
     
         18 . The flywheel device of  claim 17 , wherein the housing is configured to support the rotor, provide an alignment fixture for the lower bearing assembly, the upper bearing assembly, and a shaft of the rotor, and provide a suspension system from the rotor. 
     
     
         19 . The flywheel device of  claim 12 , wherein the housing comprises an upper housing member that provides a suspension element for the rotor. 
     
     
         20 . The flywheel device of  claim 12 , wherein the off-loading electromagnet is structurally integrated into an upper housing member of a vacuum chamber formed by the housing. 
     
     
         21 . The flywheel device of  claim 12 , wherein the housing comprises an upper housing member, a bottom plate, and a cylindrical section. 
     
     
         22 . The flywheel device of  claim 12 , wherein the off-loading force that lifts the rotor against the upper bearings in the vertical direction causes the rotor to apply a vertical force to the upper bearings.