Abstract:
Embodiments of the invention relate generally to lead path configurations in generator rotors and, more particularly, to a support apparatus for a main lead and generator rotors incorporating such a support apparatus. In one embodiment, the invention provides a support apparatus for a main lead of a generator rotor, the support apparatus comprising: a cross-sectionally L-shaped body having: a first portion; and a second portion substantially perpendicular to the first portion, wherein the first portion includes an arcuate first surface for interfacing with a centering ring of the generator rotor and an arcuate second surface adapted to be substantially parallel to a rotor shaft of the generator rotor; a main lead passage extending along the arcuate first surface of the first portion and through the second portion.

Description:
BACKGROUND OF THE INVENTION 
     Embodiments of the invention relate generally to lead path configurations in generator rotors and, more particularly, to a support apparatus for a main lead and generator rotors incorporating such a support apparatus. 
     Generator rotors include an axial rotor surrounded, at least in part, by an annular stator. As the rotor rotates, an electrical current is generated in conductive coil windings within the stator. An electrically conductive lead path forms a loop from an exciter, into the coil windings, and back. Over extended periods of operation, however, physical stresses can lead to partial or complete severing of the lead path. As a consequence, the conductive quality of the lead path may be diminished, current may be lost to nearby conductive materials, and/or electrical arcing may result. Arcing and loss of current to other conductive materials may melt or otherwise damage the generator rotor or other generator components. 
     BRIEF DESCRIPTION OF THE INVENTION 
     In one embodiment, the invention provides a support apparatus for a main lead of a generator rotor, the support apparatus comprising: a cross-sectionally L-shaped body having: a first portion; and a second portion substantially perpendicular to the first portion, wherein the first portion includes an arcuate first surface for interfacing with a centering ring of the generator rotor and an arcuate second surface adapted to be substantially parallel to a rotor shaft of the generator rotor; a main lead passage extending along the arcuate first surface of the first portion and through the second portion. 
     In another embodiment, the invention provides a generator rotor comprising: a rotor shaft including an internal conductive bore; a main terminal electrically connected to the conductive bore; a plurality of rotor coil windings, including a plurality of coil end straps; a centering ring adjacent the plurality of coil windings; a support apparatus for supporting a main lead and attached to the centering ring, the support apparatus comprising: a cross-sectionally L-shaped body having: a first portion; and a second portion substantially perpendicular to the first portion, wherein the first portion includes an arcuate first surface for interfacing with a centering ring of the generator rotor and an arcuate second surface adapted to be substantially parallel to a rotor shaft of the generator rotor; a main lead passage extending along the arcuate first surface of the first portion and through the second portion; and a main lead extending from the main terminal, through the main lead passage of the support apparatus, along the plurality of rotor coil windings, to at least one of the plurality of coil end straps. 
     In yet another embodiment, the invention provides a generator rotor comprising: a rotor shaft including an internal conductive bore; a main terminal electrically connected to the conductive bore; a plurality of rotor coil windings, including a plurality of coil end straps; a non-metallic support channel comprising an elongate, axially-oriented channel; and at least one protrusion extending from the elongate, axially-oriented channel to a position between two of the plurality of coil end straps; and a main lead extending from the main terminal, through the elongate, axially-oriented channel of the non-metallic support channel, to at least one of the plurality of coil end straps. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       These and other features of this invention will be more readily understood from the following detailed description of the various aspects of the invention taken in conjunction with the accompanying drawings that depict various embodiments of the invention, in which: 
         FIG. 1  shows a cross-sectional side view of a typical air-cooled generator rotor lead path. 
         FIG. 2  shows a cross-sectional side view of a typical liquid-cooled generator rotor lead path. 
         FIGS. 3 and 4  show perspective and side views, respectively, of a main lead support apparatus according to an embodiment of the invention. 
         FIG. 5  shows a cross-sectional side view of a generator rotor lead path including the main lead support of  FIGS. 3 and 4 , according to an embodiment of the invention. 
         FIGS. 6 and 7  show perspective views of attaching devices for attaching a main lead along a portion of a lead path according to an embodiment of the invention. 
         FIG. 8  shows a cross-sectional side view of a generator rotor lead path according to an embodiment of the invention. 
         FIG. 9  shows a cross-sectional view of a non-metallic support channel according to an embodiment of the invention. 
     
    
    
     It is noted that the drawings of the invention are not to scale. The drawings are intended to depict only typical aspects of the invention, and therefore should not be considered as limiting the scope of the invention. In the drawings, like numbering represents like elements among the drawings. 
     DETAILED DESCRIPTION OF THE INVENTION 
     Turning now to the drawings,  FIG. 1  shows a cross-sectional side view of a lead path  20  in a known air-cooled generator  100  comprising a rotor body  10  and rotor shaft  12 . 
     Bore copper  22  (i.e., a conductive material along an internal bore of rotor shaft  12 ) extends axially through rotor shaft  12  and a main terminal  24  extends radially to rotor coil windings  30 . Where main terminal  24  electrically connects with rotor coil windings  30 , a gooseneck member  26  is commonly employed. Other components of generator  100  include a retaining ring  14 , a centering ring  16 , and a fan mount  40 . Rotor coil windings  30  include a plurality of coil end straps  32 . Coil-to-coil connectors  34 ,  36  connect adjacent coils alternately at the bottoms and tops, respectively, of coil end straps  32  to complete the circuit. Generators with lead path configurations such as that shown in  FIG. 1  often experience lead path failures in the area of gooseneck member  26 . 
     It is noted that  FIG. 1  and similar figures described below show only a portion of a generator most relevant to description of the various embodiments of the invention. Rotor body  10  and rotor shaft  12 , for example, extend below bore copper  22  and both into and out of the page, as will be apparent to one skilled in the art. 
       FIG. 2  shows a cross-sectional side view of a lead path  120  in a known liquid-cooled generator  200 . Main terminal  124  extends radially from bore copper  122 . Main lead  128  extends from main terminal  124 . Lead path configurations such as that shown in  FIG. 2  typically require one or more lead wedges  150  to retain main lead  128  in position along rotor body  110 . In some configurations, a slot is cut into rotor body  110 , into which main lead  128  lies. A J-strap  126  makes the connection to rotor coil windings  130  and is often a point at which lead path failures are experienced. 
     As will be explained in greater detail below, advantages that may be realized in the practice of some embodiments of the described invention include avoidance of the need for a separate slotting operation to form a slot into which the main lead lies and elimination of the need for lead wedges. Avoiding these additional steps and components may reduce costs and simplify the manufacture, assembly, and maintenance of generators in which the various embodiments of the invention are incorporated. 
       FIG. 3  shows a perspective view of a support apparatus  300  for supporting a main lead along a portion of a lead path, according to one embodiment of the invention. Support apparatus  300  includes a first body portion  210  and a second body portion  230  arranged substantially perpendicular thereto, to form an “L” shape in cross-section. First body portion  210  includes a first face  212 , a first arcuate top surface  214  substantially perpendicular to first face  212 , and an arcuate bottom surface  216  substantially perpendicular to first face  212  and substantially parallel to first arcuate top surface  214 . First body portion  210  has a thickness T. 
     As used herein, the terms “top” and “bottom” are intended to refer merely to relative positions within the figures shown. Inversion of support apparatus  300 , for example, would result in first arcuate top surface  214  lying beneath arcuate bottom surface  216 . 
     Second body portion  230  includes a second face  232  substantially parallel to first face  212  and separated therefrom by a depth D of first arcuate top surface  214 . A second arcuate top surface  234  lies substantially parallel to first arcuate top surface  214  and is separated therefrom by a height H of second body portion  230 . A height of support apparatus  300  includes height H and thickness T. Support apparatus  300  includes an edge  244  at which each of first face  212 , first arcuate top surface  214 , arcuate bottom surface  216 , second face  232 , and second arcuate top surface  234  terminates. (A second, similar edge  246  is shown in  FIG. 4 , described below.) 
     A main lead passage  220  extends from first face  212  through first body portion  210  to an opening (shown in  FIG. 4  below) in second body portion  230  and extends from first arcuate top surface  214  into first body portion  210  to a depth less than thickness T. That is, main lead passage  220  forms a void through which a main lead may pass through, and be supported by, support apparatus  300 . 
     In  FIG. 3 , support apparatus  300  is shown further including fastener holes  240 ,  242  which, as will be described in greater detail below, may be employed to attach support apparatus  300  to a centering ring of a generator rotor. Fasteners may include, for example, bolts, rivets, and screws. Other fastening devices and mechanisms may similarly be used and are within the scope of the invention, as will be apparent to one skilled in the art. Similarly, while support apparatus  300  is shown in  FIG. 3  including two fastener holes  240 ,  242 , more or fewer fastener holes or similar fastening/coupling devices and mechanisms may be employed in other embodiments of the invention. 
       FIG. 4  shows a side view of support apparatus  300 , as viewed facing second body portion  230  with first body portion  210  hidden and shown in phantom. In some embodiments, both first body portion  210  and second body portion  230  are non-metallic. Non-metallic materials suitable for inclusion in first body portion  210 , second body portion  230 , or both, include, for example, nylons, polyethylenes, rubbers, ceramics, and glasses. Other suitable materials will be apparent to one skilled in the art and are within the scope of the invention. 
     In other embodiments, first body portion  210 , second body portion  230 , or both, may include metallic materials. Suitable metallic materials include, for example, steel, brass, copper, aluminum, titanium, and alloys thereof. Other metallic materials are also included within the scope of the invention, as will be recognized by one skilled in the art. In embodiments where metallic materials are included in first body portion  210  and/or second body portion  230 , an insulating layer  222  may be included within main lead passage  220 . 
     In  FIG. 4 , a similar insulating layer  218  may be included along arcuate bottom surface  216 . Suitable insulating materials for use in insulating layers  218 ,  222  include, for example, ceramics and glasses, such as epoxy glass. Other insulating materials may be employed, as will be recognized by one skilled in the art, and are within the scope of the invention. 
       FIG. 5  shows a cross-sectional side view of a generator rotor  400  according to an embodiment of the invention. Support apparatus  300  is shown attached to centering ring  316 . Main lead  328  passes from a main terminal  324 , through support apparatus  300  (i.e., through main lead passage  220  ( FIGS. 3-4 )) and along rotor coil windings  330 . Main lead  328  may be supported along rotor coil windings  330  by a plurality of attaching devices  500  attached to coil-to-coil connectors  334 . 
     Several advantages may be realized in practicing the embodiment of the invention shown in  FIG. 5 . Both the slotting and lead wedges typical of lead path configurations such as that shown in  FIG. 2  are eliminated. The gooseneck member ( 26  in  FIG. 1 ) typical of other configurations is similarly eliminated. Servicing of main terminal  324  and other components of the lead path  320  is easier and requires less or no disassembly of generator rotor components. The positioning of main terminal  324  closer to fan mount  340  provides greater cooling of main terminal  324  than in other lead path configurations. 
     Significantly, the lead path configuration shown in  FIG. 5  and similar configurations according to other embodiments of the invention are suitable for use in both air-cooled generator rotors and liquid-cooled generator rotors. That is, a single lead path configuration may be scaled according to the duty requirements of the generator rotor. As shown in  FIGS. 1 and 2 , significantly different lead path configurations are currently used in air-cooled and liquid-cooled generator rotors. 
       FIG. 6  shows a perspective view of attaching device  500  of  FIG. 5 . In the embodiment of  FIG. 6 , attaching device  500  includes a first body member  410  and a second body member  420 , which may be secured together by a pair of fasteners  430 ,  432 . In use, first body member  410  would typically be placed over a coil-to-coil connector ( 334  in  FIG. 5 ) and the main lead ( 328  in  FIG. 5 ) positioned beneath the coil-to-coil connector, and both secured from below by second body member  420 . In some embodiments, the coil-to-coil connector and main lead are separated by an insulating material  422 , such as may be used in insulating layers  218 ,  222  ( FIG. 4 ), as described above. 
       FIG. 7  shows another embodiment of an attaching device  600  in which the body  510  is unitary and secured by a single fastener  530 . Use of attaching device  600  is similar to that described above with respect to the embodiment of  FIG. 6 . 
       FIG. 8  shows a cross-sectional side view of a generator rotor  700  having a lead path  620  according to another embodiment of the invention. In  FIG. 8 , main lead  628  is enclosed within a non-metallic support channel  900  beneath rotor coil windings  630 . Support channel  900  includes an elongate, axially-oriented channel  810  and a plurality of protrusions  820 ,  822 ,  830 ,  832 . Some protrusions  820 ,  822  extend upward (i.e., away from rotor body  610 ) from channel  810  to reside between adjacent coil-to-coil connectors  634  and/or adjacent coil end straps  632 , thereby restricting movement of support channel  900  and main lead  628  in non-axial directions. In order to permit axial movement of main lead  628  and/or rotor coil windings  630 , a width of protrusions  820 ,  822  is preferably less than a space between coil end straps  632  adjacent alternate coil-to-coil connectors  634 . In some embodiments, to prevent or reduce movement of main lead  628  in non-axial directions, one or more attaching devices, such as those shown in  FIGS. 6 and 7 , may be used to secure channel  810  to coil-to-coil connectors  634 . 
     Other protrusions  830 ,  832  extend downward (i.e., toward rotor body  610 ) from channel  610  to reside along or adjacent rotor body  610 , thereby restricting movement of support channel  900  and main lead  628  toward rotor body  610 . 
     Support channel  900 , including channel  810  and protrusions  820 ,  822 ,  830 ,  832  are non-metallic and may include any number of non-metallic materials. Suitable materials include, for example, glasses and ceramics. In some embodiments, support channel  900  is comprised primarily or exclusively of an epoxy glass. 
       FIG. 9  shows a cross-sectional view of support channel  900 . Protrusion  822  extends upward (i.e., away from rotor body  610  ( FIG. 8 )) and protrusion  832  extends downward (i.e., toward rotor body  610 ) from channel  810 . Main lead  628  resides within channel  810  and above protrusion  832 . 
     The terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the disclosure. As used herein, the singular forms “a”, “an” and “the” are intended to include the plural forms as well, unless the context clearly indicates otherwise. It will be further understood that the terms “comprises” and/or “comprising,” when used in this specification, specify the presence of stated features, integers, steps, operations, elements, and/or components, but do not preclude the presence or addition of one or more other features, integers, steps, operations, elements, components, and/or groups thereof. 
     This written description uses examples to disclose the invention, including the best mode, and also to enable any person skilled in the art to practice the invention, including making and using any devices or systems and performing any related or incorporated methods. The patentable scope of the invention is defined by the claims, and may include other examples that occur to those skilled in the art. Such other examples are intended to be within the scope of the claims if they have structural elements that do not differ from the literal language of the claims, or if they include equivalent structural elements with insubstantial differences from the literal language of the claims.