Abstract:
A tool for shaping generator bars for large power generators. In particular, a tool for shaping a stator bar out of a straight unprocessed bar.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
       [0001]    This application claims priority to PCT/EP2014/065887 filed Jul. 24, 2014, which claims priority to EP Application No. 13180905.5 filed Aug. 19, 2013, both of which are hereby incorporated in their entirety. 
     
    
     TECHNIAL FIELD 
       [0002]    The present disclosure relates to a tool for making stator bars for large power generators. More particularly, the present disclosure relates to a tool for shaping a stator bar out of a straight unprocessed bar. 
       BACKGROUND 
       [0003]    State-of-the-art electric energy conversion relies on a three-phase power network with alternating currents (AC) at 50 Hz or 60 Hz frequency and a voltage levels ranging from several hundreds of Volts to hundreds of thousands of Volts. The conversion of rotating mechanical energy into electric energy and vice versa is done by generators and by motors respectively. Those rotating machines can be divided into asynchronous and synchronous apparatuses. The three-phase windings of such machines comprise Copper strands which after Roebelling form a conductor. The windings also require groundwall insulation, especially in the slot section. An assembly consisting of a Roebel conductor in the center and of surrounding groundwall insulation is commonly referred to as a stator bar. 
         [0004]    When making stator bars, the conductor needs to be shaped. This disclosure uses the terms shaping stator bars and shaping the conductors inside a stator bar interchangeably. Unless otherwise indicated, the expression shaping a stator bar means shaping the conductors inside a stator bar. 
         [0005]    The process of shaping is carried out in several steps involving a plurality of workbenches and gates. Typically, the first stage and the second stage bending are carried out at gate. Subsequently, the main involute is shaped Also, the ends of the stator bar are shaped, then the bar is consolidated and finally lugs at the end of the stator bar are brazed onto the bar. The purpose of the lugs is electric contact between the stator bars of a power generator. Another purpose of the lugs is electric contact to the terminals of the generator. 
         [0006]    A number of approaches are mentioned in literature that try and overcome the above issues. U.S. Pat. No. 7,530,161 discloses a modular quick-form tooling system and stator bar set-up method. According to this application, a plurality of bend-forming tools  32 ,  33  are mounted on a support structure  31 . A stator bar  20  is then inserted in between a guide portion  35  and the bend-forming tools  32 ,  33  to shape the stator bar  20 . 
         [0007]    U.S. Pat. No. 7,275,300 discloses a process for rewinding stator bars of a power generator. The process disclosed in U.S. Pat. No. 7,275,300 involves a quick form shown on  FIG. 4  of the specification. The form is used to define the shapes of replacement stator bars during manufacturing. It fixates the core section  40  of a stator bar to end arm fixtures  42  on either end of the core section  40 . The form also provides a lever to assist the bending process. 
         [0008]    Yet another approach is disclosed on the internet http://www.vincent-industrie.com/en/activities/electrical/88-turbo-bars-forming-machine-tbfm.html. The machine disclosed therein uses a forming head and an involute support clamp to form stator bars for hydro- and for turbogenerators. The machine uses brushless motors to allow for accurate positioning of the stator bars during the forming process. Also, the stator bar forming machine is able to automatically load and unload bars in order to save time. 
         [0009]    The established processes for making stator bars have several disadvantages. The sourcing time for the tool used for shaping the main involute is several weeks. Also, the process for setting up and adjusting that tool is known to be time-consuming. The process of shaping a generator bar is known to take as long as 4.5 (four and a half) hours. 
         [0010]    The present disclosure is oriented towards providing the aforementioned needs and towards overcoming the aforementioned difficulties. 
       SUMMARY 
       [0011]    The object of the present disclosure is a tool and a method that reduces the time required for shaping stator bars. This object is achieved by a tool and by a method according to the independent claims of this disclosure. 
         [0012]    It is another object of the present disclosure to provide and tool and a method that are versatile. This means that a variety of different shapes of stator bars can be obtained by using the same tool or method. 
         [0013]    It is another object of the present disclosure to provide a tool and a method suitable for generator rewinds. During a generator rewind, the stator bars of a generator need to be replaced by replacement bars. The tool and the method disclosed herein shall in particular reduce the time required for generator rewinds. The tool and the method disclosed herein shall also be versatile to allow rewinds of generators with a variety of different shapes of stator bars. 
         [0014]    It is another object of the present disclosure to bring down the time required for preparation and adjustment of known tools. In a preferred embodiment, the time for preparation and adjustment shall be brought down from three weeks to three days. 
         [0015]    It is another object of the present invention to come up with a modular tool for shaping stator bars. Modularity ensures the tool can easily be adapted to accommodate different sizes and shapes of stator bars. 
     
    
     
       BRIEF DESCRIPTION OF DRAWINGS 
         [0016]    The foregoing objects and many of the attendant advantages of this invention will become more readily appreciated as the same becomes better understood by reference to the following detailed description when taken in conjunction with the accompanying drawings, wherein: 
           [0017]      FIG. 1  provides a three-dimensional drawing of the complete tool for shaping stator bars of power generators. 
           [0018]      FIG. 2  shows an index tower  5  in three dimensions. 
           [0019]      FIG. 3  provides a side-view of a roller  20 . 
           [0020]      FIG. 4  shows a front-view of the roller  20 . 
           [0021]      FIG. 5  provides another side-view of the roller  20 . 
       
    
    
     DETAILED DESCRIPTION 
       [0022]      FIG. 1  is a three-dimensional representation of the complete tool for shaping stator bars of power generators. The complete tool comprises a foundation  1 . Two gates  2 ,  3  are mounted on the foundation  1 . Each of the gates  2 ,  3  corresponds to a workbench where a number of stages of the shaping process are carried out. The first and the second stage of the shaping process are carried out by a set of tools  4  comprised in both gates. 
         [0023]    Gate  2  comprises a plurality of index towers  5 . The index towers  5  are used to shape the stator bars and are adjustable as will be described further on. The machine has got a total of 14 index towers. Another preferred embodiment comprises less than 20 index towers  5 . A more preferred embodiment comprises less than 12 index towers  5 . Yet another preferred embodiment comprises less than 8 index towers. 
         [0024]    The complete tool may comprise one or several fixed electrical installations  6 . These fixed electrical installations  6  would typically be arranged in cubicles and be mounted to the factory floor. Electronic equipment such as relays, programmable logic controllers, computers and fuses to control the process of shaping generator bars are typically arranged inside the cubicles  6 . 
         [0025]    The complete tool may also comprise a platform  7  to provide space for an operator  8 . The operator would typically control and interfere with the bending process through a control cabinet  9 . The gate control cabinet  9  will typically be connected to the cubicles  6 , where the operator&#39;s commands are processed by various electronic processing means. 
         [0026]    The index towers  5  may actuate in response to commands that are delivered directly by the control cabinet  9 . The index towers  5  may also actuate based on commands that are entered in the control cabinet  9  and delivered through the cubicles  6 . It seems worth noting the complete tool can be run either fully automated or partially manually operated through an operator  8 . 
         [0027]      FIG. 2  shows an index tower  5  in three dimensions. The index tower  5  comprises a rail  10 . A clamp assembly  11  can be shifted along that rail  10  by turning a wheel  12 . The wheel  12  can either be operated manually or through a (brushless) motor (not shown on this drawing). The wheel  12  is preferably connected to a lead screw and shifts the clamp assembly  11  along the rail  10  through a nut. 
         [0028]    Another set of two rails  13  allows the clamp assembly  11  to be shifted in a direction substantially perpendicular to the direction of the first rail  10 . A wheel  14  is mounted on one end of the set of rails  13  and is connected to another lead screw  15 . By turning the wheel  14  and the lead screw  15  the rail  10  with the clamp assembly  11  can be shifted along the set of rails  13 . Like the wheel  12 , the wheel  14  can be operated either manually or automatically through a (brushless) motor. All adjustable axes have locking mechanisms included. 
         [0029]    In another embodiment, the lead screws are replaced by belts or chains that are either driven manually or operated automatically. 
         [0030]    Preferably, the index tower  5  comprises a support structure with holes  16  that allow fixation of the index tower  5  to foundation  1  of the complete tool. In a preferred arrangement, there are four such holes  16 . Fixation would typically be carried out through bolted connections, welded connections or rivets are also envisaged. 
         [0031]    The clamp assembly  11  comprises two brackets  17   a ,  17   b . The brackets  17   a ,  17   b  fix a stator bar during the shaping process. The brackets  17   a ,  17   b  are configured to withstand the forces that occur when shaping a stator bar made of metal, in particular a stator bar made of Copper or of an Aluminum alloy. To that end, the brackets  17   a ,  17   b  preferably engage or disengage pneumatically or hydraulically. 
         [0032]    The brackets  17   a ,  17   b  are pivotally mounted to a support element  18 . Due to the pivotal mounting, the brackets  17   a ,  17   b  may rotate about an axis parallel to the rail  10 . The support element  18  would preferably provide a step motor to automate the rotation of the brackets  17   a ,  17   b . In another embodiment, the support element  18  provides for manual adjustment of the angle at which the brackets  17   a ,  17   b  are pivotally mounted. 
         [0033]    In another envisaged embodiment not shown on  FIG. 2 , the support  18  may rotate about an axis parallel to the set of rails  13 . This embodiment gives the index tower  5  another degree of freedom by allowing for the clamp assembly  11  to rotate about one more axis. This rotation of the support  18  together with the clamp assembly  11  can also be carried out either manually or automatically through a (brushless) step motor. 
         [0034]    In a preferred embodiment, the index tower  5  comprises a housing  19 . The housing  19  is shifted together with the clamp assembly  11  along the rail  10 . The housing  19  is typically used for any electronic components such as pre-amplifiers and position indicators that are required to run and control the clamp assembly  11 . 
         [0035]      FIG. 3  gives a side-view of a roller  20 . The complete tool typically comprises a plurality of rollers  20 . These rollers  20  are movably mounted to an overhead three-axis system. That overhead three-axis system is fitted to each gate. They  20  are configured to move along a stator bar to shift the stator bar in the right position so the brackets  17   a ,  17   b  of the index towers  5  can engage. The positions of the rollers  20  typically move in three dimensions through lead screws or through belts or through chains. 
         [0036]    The rollers  20  provide a first bracket  21   a  and a second bracket  21   b . The second bracket  21   b  is pivotally (about an axis  22 ) mounted to the first bracket  21   a . The second bracket  21   b  provides a guide  25  which is pivotally mounted to the second bracket  21   b . The pivotal mounting of the guide will be described with reference to  FIG. 5 . The pivotal mounting of the second bracket  21   b  and of the guide  25  ensures the roller  20  can be adjusted to any particular shape that a stator bar may take in the bending process. 
         [0037]      FIG. 4  shows a front-view of the roller  20 . In  FIG. 4 , the second bracket  21   b  together with the guide  25  has been tilted at an angle  23  with respect to the first bracket  21   a . The tilting is a consequence of rotating the second bracket  21   b  and the guide  25  about the axis  22  shown on  FIG. 3 .  FIG. 4  also shows the second bracket  21   b  comprises first and second side-walls  24   a  and  24   b.    
         [0038]      FIG. 5  provides another side-view of the roller  20  and should be compared to  FIG. 3 . In  FIG. 5  the guide  25  has been tilted at an angle  26 . In  FIG. 5  the rotation of the guide  25  is about an axis perpendicular to the plane of the drawing. That axis stands perpendicular to the aforementioned axis  22  shown on  FIG. 3 . The rotation of the guide  25  shown on  FIG. 5  gives the roller  20  another degree of freedom and allows adjustment to any given shape of a stator bar. 
         [0039]    In a preferred embodiment, the guide  25  is mounted to the bracket  21   b  through a spring. In practice, the tensile force applied by the spring rotates the guide  25  to properly accommodate the stator bar. 
         [0040]    The aforementioned embodiments focus on shaping stator bars. It is understood by the skilled person that the same embodiments can also be used to shape rotor bars of power generator. In general, the embodiments can be applied to shape all sorts of generator bars including but not limited to stator and rotor bars. 
         [0041]    While the invention has been described in connection with what is presently considered to be the most practical and preferred embodiment, it is to be understood that the invention is not to be limited to the disclosed embodiments, but on the contrary, is intended to cover various modifications and equivalent arrangements included within the spirit and scope of the appended claims.