Electrical generator or motor structure – Dynamoelectric – Rotary
Reexamination Certificate
1999-05-05
2001-07-31
Ramirez, Nestor (Department: 2834)
Electrical generator or motor structure
Dynamoelectric
Rotary
C310S181000, C310S261100, C310S254100, C310S06800R
Reexamination Certificate
active
06268673
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to rotating machines, e.g., turbines, motors and generators, and, more particularly, to a control coil arrangement for providing rotor balance, levitation, centering, torque, and thrust control in such machines.
BACKGROUND OF THE INVENTION
Magnetic thrust bearings providing axial thrust have recently been developed to replace mechanical thrust bearings used in all types of rotating machines, e.g., turbines, motors and generators, having a rotor and a stator. These magnetic thrust bearings serve to enhance dynamic performance, reduce power loss and possibly reduce the overall length of the associated rotating machine. A typical mechanical thrust bearing and its collar are shown in
FIG. 1A
which is a schematic cross sectional view of a rotating machine. In
FIG. 1A
, a conventional stator
10
and a rotor
12
are separated by an air gap
14
. As illustrated, rotor
12
includes a projecting thrust collar
16
which rotates with rotor
12
between a fixed thrust stop
18
. A typical magnetic thrust bearing is shown in FIG.
1
B. As illustrated, the fixed thrust stop of the mechanical thrust bearing of
FIG. 1A
is replaced by a C-core solenoid coil
19
or by a variation thereof. It will be appreciated that the thrust bearing may be of smaller diameter than the machine rotor diameter and, therefore, may have limited axial force capability. Further, the overall design of the machine may place limits on the axial spacing assigned for the bearing function, thereby additionally restricting overall control.
SUMMARY OF THE INVENTION
Generally speaking, in accordance with the invention, there are provided solenoid and other coil configurations (with or without associated permanent magnets for producing an axial bias magnetic field) which are disposed at one or both axial ends of a rotating machine rotor (with or without magnetic disks), independent of the machine orientation or axis of rotation, and which afford planar axial control at single or multiple locations for rotor balance and thrust action.
According to the invention, a rotating machine is provided which comprises: a stator; a rotor adapted for rotation relative to the stator and including an active portion; and at least one fixed coil disposed adjacent to at least one end of the active portion of the rotor for producing an axially directed flux in the active portion so as to provide rotor balance, levitation, centering, torque, and thrust control.
In one preferred embodiment, the active portion includes a magnetic disk at the at least one end thereof.
In an advantageous implementation, the fixed coil comprises a C-core or E-core solenoid coil supported by a stationary member.
In an alternative advantageous implementation, the fixed coil comprises a control coil wound on a stationary member. Preferably, the stationary member comprises a plurality of axially extending elements and a separate control coil is wound on each of the elements. In an important embodiment, a permanent magnet is disposed adjacent to the fixed coil for producing a bias flux. In one preferred embodiment, a permanent magnet is secured to an end face of each of the elements. The permanent magnets advantageously comprise arcuate segments of a segmented permanent magnet of a discontinuous annular shape.
In an alternative implementation, the permanent magnet comprises a permanent magnetic disk supported on the active portion of said rotor in spaced, opposed relation with respect to the coils.
In another implementation of the embodiment discussed above, the at least one coil preferably comprises first and second coils mounted on the stationary member in radially spaced relation. The permanent magnet is preferably mounted on the stationary member in a radial plane extending between the first and second coils. Advantageously, the stationary member comprises first and second sets of axially projecting portions, the first set forming a first discontinuous annulus of a first diameter and the first coil comprising a first plurality of windings individually wound on respective projecting portions of the first set, and the second set forming a second discontinuous annulus having a diameter smaller than the diameter of the first annulus and being nested within the first annulus, and the second coil comprising a second plurality of windings individually wound on the projecting portions of the second set. Preferably, the axially projecting portions of the first and second sets each include a radially projecting arcuate base portion at an end thereof remote from the rotor and the permanent magnet includes a plurality of arcuate segments forming a discontinuous annulus, each of the arcuate segments being supported between respective pairs of opposed arcuate base portions of the axially projecting portions of the first and second sets.
A non-magnetic barrier is advantageously disposed at the at least one end for supporting the magnetic disk on the rotor.
In an advantageous embodiment, the machine includes a fixed coil disposed adjacent to each end of the active portion thereof, i.e., at both ends of the rotor. Preferably, this active portion also includes a magnetic disk at both ends thereof. Advantageously, a permanent magnet is disposed adjacent to each of the coils for producing a bias flux. In one implementation, the permanent magnet (PM) comprises a permanent magnet disk supported with each of the coils on a stationary member. In an alternative implementation, the permanent magnet comprises a permanent magnet disk supported on the active portion of the rotor in spaced, opposed relation with respect to each of the coils.
Other features and advantages of the invention will be set forth in, or apparent from, the following detailed description of preferred embodiments of the invention.
REFERENCES:
patent: 4057369 (1977-11-01), Isenberg et al.
patent: 5250865 (1993-10-01), Meeks
patent: 5315197 (1994-05-01), Meeks et al.
patent: 5705869 (1998-01-01), Kliman et al.
patent: 5734213 (1998-03-01), Oh
patent: 5818137 (1998-10-01), Nichols et al.
Lewandowski Chad R.
Shah Manoj R.
Caress Virginia B.
Gottlieb Paul A.
Lucas John T.
Perez Guillermo
Ramirez Nestor
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