Apparatus and methods for passive magnetic reductionof thrust force in rotating machines

A method for generating an axial thrust force profile in a rotating machine, comprising the steps of:

• configuring the rotating machine to comprise a first magnetic circuit comprising a rotor comprising:
• two generally parallel surfaces,
• a shaft oriented substantially perpendicular to one of the surfaces and connected to the rotor,
• one or more bearing for supporting the shaft, and
• a coil for carrying a current and generating a magnetic flux in the first magnetic circuit, and further wherein the method comprises the steps of:
• providing a first magnetic pole piece and second magnetic pole piece;
• configuring a first gap between the first magnetic pole piece and one of the surfaces;
• configuring a second gap between the second magnetic pole piece and the other surface;
• configuring the pole pieces so that current flowing in the coil induces flux to flow in a second magnetic circuit comprising the pole pieces, the gaps and the rotor;
• and
• configuring a magnetic saturation characteristic of the second magnetic circuit to provide a pre-determined axial thrust force profile as a function of the magnitude of the current flowing in the coil as the current varies over a range.

An uninterruptable power supply rotating machine providing for the reduction of axial thrust force using a passive magnetic reduction flux circuit, said rotating machine comprising:

• a housing;
• a field winding within the housing and being adapted to generate a balanced magnetic flux defining first and second portions;
• a pair of armature windings;
• a rotor, the first flux portion to flow through the housing, armature windings, and rotor;
• and
• a pair of pole pieces formed as a structural portion of said housing for passively managing the magnetic saturation of the electromagnetic circuit existing during the operation of the uninterruptable power supply
• said pair of pole pieces defining differing cross-sectional areas and being positioned between the housing and rotor, the pole pieces and the rotor defining gaps there between configured to have reluctances approximately equal to each other, the second flux portion to flow through the housing, pole pieces, gaps, and rotor, the differing cross-sectional areas to cause one of the pole pieces to saturate at a lower magnetic flux level than the other pole piece.

A passive magnetic unloading kit for a rotating machine which includes a housing;

• a field winding within the housing adapted to generate a magnetic flux;
• a pair of armature air gaps each defining a reluctance;
• and a rotor, the passive magnetic unloading kit comprising:
• a first pole piece defining a first cross-sectional area;
• and
• a second pole piece defining a second cross-sectional area which is different than the first cross-sectional area of the first pole piece;
• wherein the pole pieces are adapted to be positioned between the housing and rotor, so that the pole pieces and the rotor to define gaps there between and wherein the gaps to have reluctances approximately equal to each other,
• wherein a first portion of the magnetic flux to flow through the housing, armature windings, and rotor and wherein a second portion of the magnetic flux to flow through the housing, pole pieces, gaps, and rotor and wherein the differing cross-sectional areas to cause one of the pole pieces to saturate at a lower magnetic flux level than the other pole piece.