Radial magnetic bearing

Details Radial magnetic bearing Radial magnetic bearing

1998-06-09

2001-12-11

Dougherty, Thomas M. (Department: 2834)

Electrical generator or motor structure

Dynamoelectric

Rotary

C310S216006

Reexamination Certificate

active

06329733

ABSTRACT:

FIELD OF THE INVENTION
This invention relates to magnetic bearings, and more particularly, to radial magnetic bearings having flux paths transverse to the axis of rotation for the rotor.
BACKGROUND OF THE INVENTION
Radial magnetic bearings having flux paths transverse to the axis of rotation for the rotor are well known in the art. Traditionally, such bearings have one or more actuator cores
10
, each of which have constant cross-sectional area magnetic flux paths through the poles
12
and back iron
14
of the core
10
, as seen in FIG.
1
. The core
10
shown in
FIG. 1
is conventionally referred to as an E-core because it is E-shaped with three poles
12
extending from the back iron
14
, and a coil
16
wound around each of the three poles. The constant cross-sectional area design allows for the coils
16
to be pre-wound and then slid over the poles
12
in the radial direction during assembly. Additionally, providing a coil
16
on each of the poles
12
serves to increase the magnetic flux through each of the poles and to minimize magnetic flux leakage to the poles
12
on neighboring actuator cores
10
.
For such magnetic bearings, the maximum load capacity is determined by the bearing force generated when either the actuator cores
10
or the rotor
18
become magnetically saturated. In the traditional, constant cross-sectional area designs such as shown in
FIG. 1
, saturation typically occurs either in the back iron
14
or in the area of the coils
16
. This is undesirable because the bearing force of such magnetic bearings is proportional to the square of the magnetic flux density in the gap G between the rotor
18
and the tips of the core poles
12
. For optimum bearing actuator design, the cores
10
should be magnetically saturated close to the gap G between the tips of the poles
12
and the rotor
18
.
There is a continuing desire to improve the load capacity of radial magnetic bearings. Further, there is a desire to provide increased load capacity with little or no increase in the packaging size required for such bearings.
SUMMARY OF THE INVENTION
It is the principal object of the invention to provide a new and improved radial magnetic bearing.
It is another object of the invention to provide a radial magnetic bearing having an increased load capacity.
It is another object of the invention to provide a radial magnetic bearing having a higher load capacity than traditional radial magnetic bearings with similar packaging sizes.
An exemplary embodiment of the invention achieves at least some of the foregoing objects in a magnetic actuator core for a radial bearing that supports a rotor for rotation about an axis. The magnetic actuator core includes a back iron, and a plurality of poles spaced circumferentially about the axis and extending radially from the back iron. Each of the poles has a taper wherein the circumferential width of the pole tapers from larger to smaller as the pole extends from the back iron.
In one form of the invention, a pair of circumferentially spaced poles extend radially inward from the back iron. The poles define a coil slot extending radially inward from the back iron between the poles. The coil slot has a uniform circumferential width over substantially the entire radial length of the coil slot.
In accordance with the invention, a magnetic bearing is provided for supporting a rotor rotation about an axis. The magnetic bearing includes a plurality of actuator cores spaced circumferentially about the axis. Each of the actuator cores includes a back iron, a center pole extending radially from the back iron tip, two outer poles spaced circumferentially about the axis on opposite sides of the center pole and extending radially inward from the back iron.
In one form, a coil is wound around the center pole of each actuator core to generate a magnetic flux to support the motor. Each actuator core is characterized by the absence of a coil on either of the two outer poles.
In one form, each of the outer poles define a coil slot with the center pole of the actuator core that extends radially inward from the back iron between the outer pole and the center pole. The coil slot has a minimum circumferential width S. A circumferential gap having a circumferential width C is provided between the outer poles of circumferentially adjacent core segments, with the circumferential width C being less than the circumferential width S.


REFERENCES:
patent: 3560776 (1971-02-01), Kildishev
patent: 4983870 (1991-01-01), McSparran
patent: 5202598 (1993-04-01), Katsumata
patent: 5528210 (1996-06-01), Huang et al.
patent: 5804896 (1998-09-01), Takehara et al.

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