Abstract:
An intercoupled stator core is separated from a non-vertically oriented (including horizontal) generator frame by decoupling the stator core and frame coupling members and interposing a slidable member between them. Thereafter they are separated relative to each other on the sliding member. The sliding or slidable member may comprise a rail, or alternatively a roller adapted for rolling contact with one of the opposed stator core or generator structures and an engagement surface in contact with the other structure. A system for separating the stator core from a non-vertically oriented generator frame includes first and second raising end plates adapted coupled to axial ends of the stator core. The end plates project outwardly from the generator frame ends, for coupling to a raise mechanism. After the raise mechanism raises the stator core the slidable member is interposed between the stator core and generator frame.

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The invention relates to generator stator core removal, and more particularly to field removal and reinstallation of assembled stator cores from non-vertically oriented generator frames, including horizontally-oriented generator frames. 
     2. Description of the Prior Art 
     During a generator major overhaul stator cores are removed from the generator frame. Old core windings and insulation are stripped from the stator core lamina stack and replaced with new ones. The replacement stator core is assembled within the generator frame. Generally the overhaul is performed at the power generation site, rather than transporting the entire generator to an offsite repair facility. 
     Some generator designs facilitate removal of their entire stator core assembly as a module by orienting the core axis in a vertical position and lifting the core module with a crane or other hoisting device that is coupled to a lifting plate affixed to an axial end of the stator core. When vertically lifting an entire stator core module care must be taken to avoid damaging either the core or the generator frame by inadvertent contact during lifting. Given the relatively large diameter, axial length and weight of a stator core, and the relatively small radial clearance with the generator frame a small yaw of the stator core during the hoisting operation may cause inadvertent impacts. Cranes, hoists and similar heavy moving equipment are expensive to purchase or lease, require logistic planning to have them available on a job site and skilled operating engineers, thus often necessitating retention of specialized subcontractors to complete the generator refurbishment. It is desirable to minimize the number of subcontractors needed to refurbish a generator, as well as minimize likelihood of generator damage that might result from impacts incurred during vertical stator core hoisting. 
     Other generator designs are not suitable for vertically lifting stator cores prior to their refurbishment. In those generator designs the stator core is disassembled in place by hand. Service personnel serially and repetitively remove layers of core windings, insulation and individual core lamina (often up to 75000 individual laminations) in the lamina stack with hand-held tools while the generator frame is oriented with its rotor rotational axis in a vertical or horizontal position (analogous to an archaeological excavation). Such hand labor is time consuming and expensive. A typical in-place rotor core disassembly within the generator frame requires 3-8 days&#39; work by a service crew to remove layers of lamina, windings and insulation. Core disassembly external to the generator consumes less service time, and allows quicker generator service resumption. 
     SUMMARY OF THE INVENTION 
     Accordingly, an object of the invention is to remove a stator core from a generator as a module without vertically hoisting the core, so as to eliminate the need for cranes or other heavy hoisting equipment. 
     Another object of the invention is to remove a stator core from a generator as a module without vertically hoisting the core, so as to minimize likelihood of generator damage arising from inadvertent contact of the stator core and generator frame. 
     An additional object of the invention is to minimize hand labor required to remove a stator core from a generator, and specifically to avoid full core disassembly in place with hand labor. 
     These and other objects are achieved in accordance with the present invention by a method for separating an intercoupled stator core from a non-vertically oriented generator frame. The method features decoupling respective coupled stator core and frame coupling members. After the decoupling at least one sliding member is interposed between the stator core and frame. Thereafter the respective stator core and frame are slidably separated relative to each other on the at least one sliding member, so that they are separated from their initially coupled relative positions. The method of this invention avoids the need to hoist the stator core vertically out of the generator frame, or the need to disassemble the core in its entirety by hand. 
     The present invention also features an apparatus for separating a stator core having a first coupling member relative to a non-vertically oriented generator frame having a second coupling member in engagement with the first coupling member. The apparatus comprises a slidable member adapted for interposition between the disengaged stator core and generator frame. The slidable member enables relative sliding motion between the stator core and generator frame. In some embodiments the slidable member comprises a rail having a first surface for slidable engagement with one of the coupling members. In other embodiments the rail further comprises a second slidable surface for slidable engagement with the other of the coupling members. In yet other embodiments the slidable member comprises a roller adapted for rolling contact with one of the opposed stator core or generator structures and an engagement surface adapted for contact with the other structure. Interposition of a slidable member between the stator core and frame while the generator is oriented in a non-vertical position avoids inadvertent impact of the stator core and generator frame during their separation. 
     Other embodiments of the present invention feature a system for separating a stator core having axial ends and a first coupling member relative to a non-vertically oriented generator frame having axial ends and a second coupling member in engagement with the first coupling member. The system includes first and second raising end plates adapted for coupling to respective axial ends of a stator core. The end plates are adapted for projecting axially outwardly from respective axial ends of the generator frame, for coupling to a raise mechanism and thereafter separating the first and second coupling members when the raise mechanism raises stator core. The system also includes a slidable member adapted for interposition between the stator core and generator frame. The slidable member enables relative sliding motion between the stator core and generator frame. The invention system avoids the need to utilize cranes or other hoisting heavy equipment and avoids inadvertent impact of the stator core and generator frame during their separation. 
     The objects and features of the present invention may be applied jointly or severally in any combination or sub-combination by those skilled in the art. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The teachings of the present invention can be readily understood by considering the following detailed description in conjunction with the accompanying drawings, in which: 
         FIG. 1  shows an axial cross section of a horizontal, non-vertically oriented generator, including a generator frame and a separable stator core; 
         FIG. 2  shows a perspective fragmented view of a stator core and generator frame, including coupling members that retain them relative to each other; 
         FIG. 3  is a radial cross sectional view of stator core and generator frame coupling members, taken along  3 - 3  of  FIG. 2 ; 
         FIG. 4  is a partial fragmentary elevational view of the generator stator core of  FIG. 1 , showing stator core end plates; 
         FIG. 5  is a perspective view of the generator of claim  1  with raising end plates and a raise mechanism installed on the stator core, for raising the stator core relative to the generator frame; 
         FIG. 6  is a perspective view the generator of claim  1  with raising end plates after interposition of slidable member rails between the separated stator core and generator frame; 
         FIG. 7  is a detailed elevational perspective view showing the stator core resting on the slidable member rails, so that the core may be slidably removed from the generator frame; 
         FIG. 8  is perspective view similar to  FIG. 6 , after the stator core is slidably separated from the generator frame and resting on the slidable member rails of  FIG. 7 ; 
         FIG. 9  is a perspective view of an alternate embodiment slidable member, including rollers; and 
         FIG. 10  is a detailed elevational perspective view showing the stator core resting on the slidable member rollers of  FIG. 9 , so that the core may be slidably removed from the generator frame. 
     
    
    
     To facilitate understanding, identical reference numerals have been used, where possible, to designate identical elements that are common to the figures. 
     DETAILED DESCRIPTION 
     After considering the following description, those skilled in the art will clearly realize that the teachings of the present invention can be readily utilized in separation of stator cores from generator frames by orienting them in a non-vertical position, separating them radially, such as with a lifting jack or other lifting device, and interposing at least slidable member between them. Thereafter the stator core is separated axially relative to the generator frame by sliding it on the slidable member(s). In this manner cranes or other hoisting heavy equipment is not needed to separate the stator core from the generator frame, and likelihood of inadvertent damage caused by stator core/generator frame contact is avoided. By removing the stator core as a module extensive hand labor is avoided as compared to that needed to remove portions of the core while still in the generator frame. 
     Referring to  FIGS. 1-3 , generator  20  is oriented in a horizontal position, and has a generator frame  30  with an exciter axial  32  and a turbine exciter axial end  34 . The generator  20  can also be oriented in other non-vertical positions at an inclined angle relative to the power plant floor. The generator frame  30  has a circumferential frame support  36  and a plurality of axially oriented frame coupling members, shown as spring bars  38 , which are affixed to the frame supports  36  by spring bar fasteners  39 . The generator  20  has a stator core  40  with axial ends terminating in stator core finger plates  40 A and stator core end plates  40 B. Stator core through bolts  40 C and building bolts  40 D axially retain the stack of stator laminas  42 . The stator core  30  defines a plurality of circumferential, axially aligned key slots  44  that retain stator core coupling member key bars  46 . The key bars  46  are coupled to respective spring bars  38  in radially spaced relationship by key blocks  48 . The key bars  46  and spring bars  38  are coupled together by coupling fasteners and plates  49 . Rotor  50  is rotatively mounted concentric with the bore formed within the stator core  30 . The stator core retains core windings that terminate in stator end windings  60  at each axial end of the stator. Before stator core  40  services, the generator  20  is preferably positioned horizontally in an area of the power generation facility where a repair crew has sufficient space to perform repairs. Often this will entail elevating the generator  20  from a generator pit to the industrial gas turbine service deck level by installing lift trunions on the generator frame  30  exterior and jacking the entire generator under the lift trunions. 
       FIGS. 5-8  show a first exemplary embodiment of a stator core separation system  70 , for separating a stator core  40  from its generator frame  30  while both are oriented in a non-vertical (preferably horizontal) position, and method for separating the stator core and generator frame. The rotor  50  and associated bearing brackets are removed from the generator frame  30  using known methods. Stator core end windings  60  are removed by hand from the turbine and exciter ends of the stator core  40 , exposing the respective stator core finger plates  40 A, end plates  40 B, through bolts  40 C and building bolts  40 D. The stator core  40  and generator frame  30  are decoupled, (e.g., by physically unfastening the generator frame spring bar coupling members  38  from the stator core key bar coupling members  46  and removing non-weight bearing key blocks  48 ). Stator core end raising plates  72  are affixed to the turbine and exciter ends of the stator core  40 , such as by coupling to the through bolts  40 C (with or without through bolt extensions). The end raising plates  72  have raising plate extensions  74  that project outwardly from the axial ends of the generator frame  30 . Frame end plates  76  are affixed to each of the exciter and turbine axial ends  32 ,  34  of the generator frame  30 . A raising mechanism  78 , such as a hydraulic jack, is interposed between the respective paired stator end raising plate extensions  74  and the frame end plates  76 . The raising mechanism  78  is raised; separating the stator core  40  and generator frame  30  radially, so that there is a spaced gap with no weight-bearing physical contact between them. At least one sliding member is interposed in the gap between the generator frame  30  and stator core  40 . 
     In the embodiment of  FIGS. 5-8  the sliding member comprises at least one and preferably a plurality of rails  80  resting on the generator frame  30  and extending out of the frame, where they rest on rail support  79 . In this manner the rails  80  are also placed under the stator core  40 . The raising mechanisms  78  on each end of the generator  20  are lowered, with the stator core  40  now resting on the rails  80 . Thereafter the raising mechanisms  78  and at least the frame end plate  76  that is proximal the rail support  79  are removed, so that the stator core  40  in its entirety as a modular unit may be axially separated from the generator frame  30  by sliding it on the rails  80 . As shown in  FIG. 7 , the sliding member embodiment rails  80  are interposed between the axially supportive respective coupling members: the stator core key bars  46  and generator frame spring bars  38 . The rail  80  has a key bar sliding surface  82 , which as shown is a channel formed in the rail for slidable receipt of the key bar  46 . The rail also has a spring bar sliding surface  84  that mates with the spring bar  38 . 
     An alternate exemplary embodiment of a stator core separation system is shown in  FIGS. 9 and 10 . The sliding or slidable member comprises a roller assembly  90 , and preferably an array of roller assemblies aligned axially and interposed between the generator frame  30  and stator core  40 , such as at the 5 o&#39;clock and 7 o&#39;clock circumferential positions within the generator frame  30 , between parallel rows of spring bars  38 . In this manner the entire decoupled modular stator core  40  may be separated axially from the generator frame  30  by sliding the stator core on the roller assemblies. Each roller assembly comprises a roller  92 , for abutment against the stator core  40  outer circumference and an engagement surface  94  distal the roller  92 , for engagement with the generator frame  30 . The engagement surface  92  may mate with a complimentary engagement surface formed in a removable fixture that is inserted as part of the stator core  40  separation procedures. Alternatively a complimentary engagement surface can be permanently installed in the generator frame. 
     The roller assembly  90  preferably comprises a height adjustment mechanism  96 , such as a fluid jack, screw jack, or adjustable shim stack, which facilitates selective relative radial adjustment between the generator frame  30  and stator core  40 . Advantageously if the height adjustment mechanism  96  is a lift mechanism or jack, it can be utilized to raise the stator core  40  away from the generator frame  30  without the need for end raising plates  72 /raising plate extensions  74 , frame end plates  76  or external raising mechanisms  78  that were described in connection with the previous embodiment of  FIGS. 5-8 . Elimination of the raising system components allows the stator core  40  to be separated from the generator frame  30  without removing the stator core end windings  60 , because there is no need to install end lifting plates  72  on the axial ends of the stator core. However, if desired those raising system components can also be utilized with the roller assemblies  90  of the present invention. Once the stator core  40  is supported by the roller assemblies  90 , it can be slid in the axial direction to the exterior of the generator frame  30 , transferred to a known sling and hoist assembly or other core transport system, and transported to a repair area for refurbishment. 
     Either stator core separation system embodiment may also be utilized to install a stator core  40  into a generator frame  30 . In this manner, a stator core  40  can be removed or installed in a generator  20  as a modular structure, without a need to perform core assembly or disassembly by hand within the confined space of the generator frame  30 . 
     Although various embodiments that incorporate the teachings of the present invention have been shown and described in detail herein, those skilled in the art can readily devise many other varied embodiments that still incorporate these teachings. The invention is not limited in its application to the exemplary embodiment details of construction and the arrangement of components set forth in the description or illustrated in the drawings. The invention is capable of other embodiments and of being practiced or of being carried out in various ways. Also, it is to be understood that the phraseology and terminology used herein is for the purpose of description and should not be regarded as limiting. The use of “including,” “comprising,” or “having” and variations thereof herein is meant to encompass the items listed thereafter and equivalents thereof as well as additional items. Unless specified or limited otherwise, the terms “mounted,” “connected,” “supported,” and “coupled” and variations thereof are used broadly and encompass direct and indirect mountings, connections, supports, and couplings. Further, “connected” and “coupled” are not restricted to physical or mechanical connections or couplings.