Patent Application
20140111046
The invention relates generally to bearings used in dynamoelectric machines, and more particularly, to electrically insulated bearings for use in such machines.
Conventional large, high speed dynamoelectric machines typically include a stator and a rotor that rotates about a longitudinal axis within the stator to convert mechanical energy into electrical energy. The rotor may include a shaft and a rotor body which may include coils carry current. Bearings are typically used to secure the shaft, with a bearing at each end of the shaft, and allow it to rotate freely. Depending on the type of dynamoelectric machine, electric currents can be established intentionally or produced by, e.g., magnetic imbalances, static storage, direct application of external power to the rotor shaft, and induced electricity generated in the rotor with the use of a rectified power source. Regardless of how produced, it is desirable to insulate shaft currents from the bearings.
In the absence of insulation, the shaft currents flow from the shaft through the bearing to the end shield or to a frame through a bearing on the other end of the shaft. Such current flow through the bearings may result in wear and degradation of the bearings, damage to the shaft, blackening of lubricating oil, damage or scorching of the bearing, and other undesirable consequences.
Insulated bearing rings, such as those coated with ceramic or insulating material have been used to safeguard the bearings from such degradation and damage, but existing insulated bearing rings have a number of disadvantages including long lead times for manufacture, and lack of flexibility in size and dimensions. Another method of insulating bearings from the shaft includes providing a ceramic coating on the shaft. This method suffers from the drawback of chipped ceramic, and therefore diminished insulating capacity and bearing fit, as a result of routine bearing replacement.
A first aspect of the disclosure provides a bearing ring having: an outer ring having an inner circumferential channel disposed on a radially inward surface thereof; an inner ring disposed within the outer ring and concentric therewith, the inner ring having an outer circumferential channel disposed on a radially outward surface thereof; and an insulating ring disposed between the inner ring and the outer ring. The insulating ring includes: an outer circumferential serration extending radially outward from an outer surface of the insulating ring, and an inner circumferential serration extending radially inward from an inner surface of the insulating ring. The outer circumferential channel and the inner circumferential serration are mating features, i.e., have complementary shapes, and the inner circumferential channel and the outer circumferential serration are mating features.
A second aspect of the disclosure provides a dynamoelectric machine having: a rotor and a stator at least partially surrounding the rotor, wherein the rotor includes: a first end shield disposed on a first axial end of the rotor, and a second end shield disposed on a second axial end of the rotor; and a bearing disposed axially outboard of each of the first end shield and the second end shield. At least one of the bearings is insulated using a bearing ring including: an outer ring having an inner circumferential channel disposed on a radially inward surface thereof; an inner ring disposed within the outer ring and concentric therewith, the inner ring having an outer circumferential channel disposed on a radially outward surface thereof; and an insulating ring disposed between the inner ring and the outer ring. At least one of the first end shield and the second end shield are electrically insulated from the bearing disposed axially outward thereof.
A third aspect of the disclosure provides a method for forming an insulated bearing ring, the method including: providing an outer ring having a first diameter and an inner circumferential channel disposed on a radially inward surface thereof; providing an inner ring having a second diameter that is smaller than the first diameter, and an outer circumferential channel disposed on a radially outward surface thereof, inserting the inner ring into the outer ring such that the inner ring and the outer ring are substantially concentric; and injecting an insulating material into an annular space between the inner ring and the outer ring.
These and other aspects, advantages and salient features of the invention will become apparent from the following detailed description, which, when taken in conjunction with the annexed drawings, where like parts are designated by like reference characters throughout the drawings, disclose embodiments of the invention.
It is noted that the drawings of the disclosure are not necessarily to scale. The drawings are intended to depict only typical aspects of the disclosure, and therefore should not be considered as limiting the scope of the disclosure. In the drawings, like numbering represents like elements between the drawings.
At least one embodiment of the present invention is described below in reference to its application in connection with the operation of a dynamoelectric machine. Although embodiments of the invention are illustrated relative to a dynamoelectric machine in the form of a generator, it is understood that the teachings are equally applicable to other electric machines including, but not limited to, other types of generators and motors. Further, at least one embodiment of the present invention is described below in reference to a nominal size and including a set of nominal dimensions. However, it should be apparent to those skilled in the art that the present invention is likewise applicable to any suitable generator and/or motor. Further, it should be apparent to those skilled in the art that the present invention is likewise applicable to various scales of the nominal size and/or nominal dimensions.
As indicated above, aspects of the invention provide an insulated bearing ring and a dynamoelectric machine having an insulated bearing ring.
As shown in
In a complete bearing ring 100, inner ring 120 is disposed within outer ring 110 and positioned such that inner ring 120 and outer ring 110 are substantially concentric. The outer diameter of inner ring 120 is smaller than the inner diameter of outer ring 110, such that when inner ring 120 is disposed within outer ring 110, an annular space remains between inner ring 120 and outer ring 110. Insulating ring 130, shown in
As shown in
Insulating ring 130 may further include at least one outer axial channel 160, shown in
Insulating ring 130 may further include a substantially circumferential flange 180 disposed on an end of the insulating ring 130, as shown in
Bearing ring 100 may be used in a dynamoelectric machine such as a generator 400 or motor to support rotor 300 and insulate the bearing.
Referring back to
A method for forming insulated bearing ring 100 is also provided. An outer ring 110 (
Insulating ring 130 is provided with an outer circumferential serration 140 extending radially outward from an outer surface of the insulating ring 130. Outer serration 140 is formed when injected insulating material is forced into inner circumferential channel 115. As a result, outer serration 140 and inner circumferential channel 115 have mating shapes and dimensions, i.e., outer serration 140 and inner circumferential channel 115 are complementary to one another. Insulating ring 130 is further provided with an inner circumferential serration 150 extending radially inward from an inner surface of the insulating ring 130, wherein the inner serration 150 mates with the outer circumferential channel 125. Inner circumferential serration 150 is similarly formed when injected insulating material is forced into outer circumferential channel 125.
As shown in
Once assembled, bearing ring 100 (
As used herein, the terms “first,” “second,” and the like, do not denote any order, quantity, or importance, but rather are used to distinguish one element from another, and the terms “a” and “an” herein do not denote a limitation of quantity, but rather denote the presence of at least one of the referenced item. The modifier “about” used in connection with a quantity is inclusive of the stated value and has the meaning dictated by the context (e.g., includes the degree of error associated with measurement of the particular quantity). The suffix “(s)” as used herein is intended to include both the singular and the plural of the term that it modifies, thereby including one or more of that term (e.g., the metal(s) includes one or more metals). Ranges disclosed herein are inclusive and independently combinable (e.g., ranges of “up to about 25 mm, or, more specifically, about 5 mm to about 20 mm,” is inclusive of the endpoints and all intermediate values of the ranges of “about 5 mm to about 25 mm,” etc.).
While various embodiments are described herein, it will be appreciated from the specification that various combinations of elements, variations or improvements therein may be made by those skilled in the art, and are within the scope of the invention. In addition, many modifications may be made to adapt a particular situation or material to the teachings of the invention without departing from essential scope thereof. Therefore, it is intended that the invention not be limited to the particular embodiment disclosed as the best mode contemplated for carrying out this invention, but that the invention will include all embodiments falling within the scope of the appended claims.
