Patent Publication Number: US-2017358968-A1

Title: Supporting device and method for supporting winding coils in a wind turbine generator

Description:
BACKGROUND 
     The present disclosure relates to devices and methods for supporting winding coils in a wind turbine generator. 
     Common rotating electrical machines, such as wind turbine generators, include a stator core with a number of stator core slots arranged around a circumference and adapted to receive stator coil windings to form a winding coil capable of generating a back electromagnetic force due to the magnetic flux generated by a rotor excitation device. A rotor is coaxially provided either within or outside the stator core such that a gap is defined between the rotor and stator core. 
     The coil windings are typically retained into the stator core slots through the use of wedges fitted in the slots. Since clearances in the slots may increase over time, flexible ripple springs are used in addition to the wedges. 
     Some systems retain coil windings into the stator slots by means of sets of wedges. Additionally, rigid filler strips and ripple springs are held between the wedges and the coil windings to fill the radial space between them. The ripple springs are compressed in a substantially flattened condition and bonded to the rigid filler strips through an adhesive. The ripple spring are thus compressed from a relaxed state into a constrained spring-loaded state. The filler strips and the ripple springs adhered to each other are inserted into the slots in the space between the wedge and the coil winding and the temperature in the slot is raised such that the adhesive is broken whereby the spring expands to load the winding in the slot. 
     Solutions for compensating for the increase of clearances in the slots rely upon the use of a number of different parts such as wedges, filler strips and ripple springs. This results in a cumbersome, complex and costly devices and process installation methods. 
     BRIEF DESCRIPTION 
     A supporting device for supporting winding coils in a wind turbine generator is disclosed herein including a flexible member that is adapted to be attached between two adjacent stator portions. Before attachment, that is, before being inserted between two adjacent stator portions, the flexible member is in a relaxed configuration, i.e. in an uncompressed condition. Once the flexible member has been properly inserted between two adjacent stator portions, the flexible member is in an operating configuration, i.e. in a compressed condition, that is, the flexible member is compressed by the stator portions and the winding coils of the wind turbine generator, applying a force on the winding coils for retaining them into slots formed in the stator core of the generator. 
     The winding coils are thus efficiently supported in the stator core of the generator through a simple, lightweight and small supporting device which is very easy to install and economical to manufacture. The present supporting device actively supports the winding coils fixed in position and allows vibrations to be efficiently minimized by applying a force on the winding coils while, in turn, prevents the winding coils from falling down. 
     The flexible member may be, for example, a leaf spring made of a flexible and/or elastic material such as, for example, fiberglass or similar, suitable for applying a force to the winding coils as stated above for fixing or retaining them into the stator core slots. In an embodiment of the present invention, the present support device is adapted to be fitted between stator portions without interfering the air gap between the generator rotor and the generator stator. 
     In the above mentioned relaxed configuration or uncompressed condition of the flexible member before it is inserted between two adjacent stator portions, the flexible member may have a substantially concave configuration. A substantially concave configuration means herein that flexible member has a shape that is rounded, curved or arched inward like the inside of a circle or sphere. 
     In the above mentioned operating configuration or compressed condition of the flexible member once it has been inserted between two adjacent stator portions, the flexible member may have a substantially flattened configuration. A substantially flattened configuration means herein that the flexible member has a substantially flat shape, with no slopes or curvatures. 
     The supporting device may also include a pre-tensioning tool for bringing the flexible member into a configuration allowing it to be inserted between two adjacent stator portions. The pre-tensioning tool is suitable to be applied to the flexible member such that the flexible member is deformed elastically into an inserting configuration allowing the flexible member to be arranged between two adjacent stator portions before reaching a final, operating position. 
     In the above mentioned inserting configuration of the flexible member for allowing it to be inserted between two adjacent stator portions, the flexible member may have a substantially convex configuration. A substantially convex configuration means herein that the flexible member has a shape that is rounded, curved or arched outward like the exterior of a circle or sphere. 
     In any case, the inserting configuration is substantially opposed to the relaxed configuration while the operating configuration is an intermediate condition between the relaxed configuration and the inserting configuration. 
     In one example, the pre-tensioning tool may have two separate walls and a tightening element. The tightening element is arranged such that as it is tightened to the flexible member, the separate walls of the tool push on opposite edges of the flexible member tending to bring it into the above mentioned inserting configuration allowing the flexible member to be inserted between the stator portions. 
     The tightening element of the pre-tensioning tool may be, for example, a screw adapted to be screwed on a winding coil coupling portion of the flexible member. As the screw of the pre-tensioning tool is screwed on such winding coil coupling portion of the flexible member, the walls of the pre-tensioning tool push on the flexible member to bring it into the inserting configuration. 
     The above mentioned coupling portion of the flexible member may be adapted to be at least partially inserted into a gap formed between adjacent winding coils when in the operating configuration. Such winding coil coupling portion may be adapted to be always in contact with adjacent winding coils when in the operating configuration. For this purpose, it may be configured in a number of different ways. For example, the winding coil coupling portion may be movable with respect to the stator portions to adapt to the gap between adjacent winding coils. In a further example, the winding coil coupling portion may have at least one projection extending outwards to adapt to the gap between adjacent winding coils. 
     A method for supporting winding coils in a wind turbine generator may be carried out using the above supporting device as follows. 
     Specifically, one or more of the above described supporting devices are provided, each including a flexible member in the relaxed configuration. Then, the flexible member is arranged into an inserting configuration so that it can be inserted between two adjacent stator portions. 
     The inserting configuration of the flexible member can be obtained by applying the above described pre-tensioning tool. The pre-tensioning tool is applied to the flexible member and tightened thereto causing the separate walls of the tool to push on opposite edges of the flexible member until the inserting configuration is reached. In such inserting configuration, the flexible member can be inserted between two adjacent stator portions. 
     Afterwards, the pre-tensioning tool is untightened from the flexible member causing its separate walls to move away from the opposite edges of the flexible member until an operating configuration of the flexible member is reached. In such operating configuration, the flexible member is compressed by the stator portions and the winding coils, remaining in contact with the winding coils of the generator. 
     The flexible member thus remains attached to regions of the stator teeth having an attaching portion such as a recess for receiving the flexible member. 
     Once the supporting device has been properly fitted between adjacent stator portions supporting the winding coils of the generator, the pre-tensioning tool can be finally removed from the flexible member. 
     In one aspect, reduction in manufacturing and assembly are achieved with the above supporting device while obtaining an efficient means for supporting winding coils in a wind turbine generator which is flexible and adaptable to the dimensional tolerances of the winding coils. 
     In another aspect, the present supporting device creates a number of air channels between the winding coils and the supporting device itself through which air is allowed to pass. This enhances cooling of the generator. 
     Additional objects and features of examples of the present supporting device will become apparent to those skilled in the art upon examination of the description, or may be learned by practice thereof. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       Particular examples of the present supporting device will be described in the following by way of non-limiting examples, with reference to the appended drawings, in which: 
         FIG. 1  is a sectional elevation of one example of a supporting device in a relaxed configuration; 
         FIG. 2  is a sectional elevation of the example of the supporting device in an inserting configuration before being inserted between two adjacent stator portions and provided with a pre-tensioning tool applied thereto; 
         FIG. 3  is a sectional elevation of the example of the supporting device in an operating configuration already inserted between two adjacent stator portions with the pre-tensioning tool being removed from the supporting device; 
         FIG. 4  is a sectional elevation of the example of the supporting device in which the flexible member and the winding coil coupling portion are separate pieces; 
         FIG. 5  is a sectional elevation of the example of the supporting device in which the winding coil coupling portion includes projecting portions; and 
         FIG. 6  is a sectional elevation of the example of the supporting device in which the flexible member is movably coupled to the stator portion. 
     
    
    
     DETAILED DESCRIPTION 
     In the figures, the supporting device has been indicated by reference numeral  100  as a whole. The supporting device  100  is intended for supporting winding coils  120 ,  121  in a wind turbine generator. The winding coils  120 ,  121  are shown in  FIGS. 2-6  of the drawings. 
     According to the examples shown in the figures, the supporting device  100  has a flexible member  140  which in the example shown is a leaf spring made of a flexible and/or elastic material such as fiberglass or similar. Other materials are also possible as long as the flexible member  140  may be elastically deformed for being inserted between two adjacent stator portions  150 ,  151  while applying a force to the winding coils  120 ,  121  for fixing or retaining them into slots formed in the stator core of the generator (not shown). The support device  100  is adapted to be fitted between stator portions  150 ,  151  without interfering the air gap between the generator rotor and the generator stator (not shown). 
     Before the flexible member  140  is inserted between two adjacent stator portions  150 ,  151 , the flexible member  140  is in a relaxed configuration as shown in  FIG. 1 , that is, in an uncompressed condition. In this condition, the flexible member  140  has a substantially concave configuration, that is, a configuration in which the flexible member  140  is curved inward like the inside of a circle or sphere as shown in  FIG. 1 . 
     As shown in  FIGS. 2 and 3  of the drawings, the supporting device  100  also has a pre-tensioning tool  180 . The pre-tensioning tool  180  includes a base  185  with separate walls  181 ,  182  and a tightening element  190 . In the non limiting example of the pre-tensioning tool  180  shown in  FIGS. 2 and 3  of the drawings, the tightening element has a screw  190  although other tightening means are possible. The screw  190  is adapted to be screwed on a threaded hole  130  formed in a winding coil coupling portion  160  of the flexible member  140 . Thus, as the screw  190  is screwed on the threaded hole  130  of the flexible member  140 , the base  185  of the pre-tensioning tool  180  approaches the flexible member  140  and its separate walls  181 ,  182  push on the flexible member  140 . This deforms the flexible member  140  bringing it into the inserting configuration shown in  FIG. 2  in which the flexible member  140  has a substantially convex configuration, that is, curved outward like the exterior of a circle or sphere as shown in  FIG. 2 , such that it can be arranged between two adjacent stator portions  150 ,  151 . 
     After the flexible member  140  has been inserted between the two adjacent stator portions  150 ,  151 , the flexible member  140  is in an operating configuration as shown in  FIG. 3 , that is, in a compressed condition. Specifically, in this condition the flexible member  140  is compressed by the stator portions  150 ,  151  and the winding coils  120 ,  121  of the wind turbine generator. In this compressed condition of the flexible member  140 , the winding coils  120 ,  121  are actively supported in position while vibrations are reduced as a force is applied thereon by the flexible member  140  that is inserted in between. The winding coils  120 ,  121  are in turn prevented from falling down by the flexible member  140 . In this operating configuration shown in  FIG. 3 , the flexible member  140  has a substantially flattened configuration, that is, a configuration in which the flexible member  140  is substantially flat, with no slopes or curvatures. Finally, in the operating configuration of the supporting device  100  shown in  FIG. 3 , a number of air channels are created between the winding coils  120 ,  121  and the flexible member  140 . Air is allowed to pass through such channels enhancing cooling of the generator. 
     The above mentioned winding coil coupling portion  160  of the flexible member  140  may be adapted to be at least partially inserted into a gap  170  formed between adjacent winding coils  120 ,  121  when the flexible member  140  is in the operating configuration as shown in  FIG. 3 . The winding coil coupling portion  160  may be adapted to be always in contact with adjacent winding coils  120 ,  121 .  FIGS. 4-6  show examples of winding coil coupling portions  160  for achieving this. In the example shown in  FIG. 4 , the winding coil coupling portion  160  is a separate piece from the flexible member  140  which provides a self-centring feature of the coupling portion  160  with respect to the winding coils  120 ,  121 . In the example of  FIG. 5 , the winding coil coupling portion  160  has projections  161 ,  162  extending outwards from the coupling portion  160  to the adjacent winding coils  121 ,  122  to adapt to the gap  170 . In the example shown in  FIG. 6 , the supporting device  100 , which includes a flexible member  140  and a winding coil coupling portion  160 , is movable with respect to the stator portions  150 ,  151 , so that the winding coil coupling portion  160  can adapt to the gap  170 . 
     For supporting winding coils  120 ,  121  in the stator of a wind turbine generator, a number of the above described supporting devices  100  may be provided with their flexible member  140  in the relaxed, uncompressed configuration as shown in  FIG. 1 . A pre-tensioning tool  180  is applied to the flexible members  140  in order to bring them into the inserting configuration shown in  FIG. 2 . For this purpose, the screw  190  of the pre-tensioning tool  180  is screwed on the threaded hole  130  of the coupling portion  160  of the flexible member  140 , thus causing the separate walls  181 ,  182  of the tool  180  to push on corresponding opposite edges  141 ,  142  of the flexible member  140  so that the flexible member  140  is elastically deformed into the inserting configuration shown in  FIG. 2 . In such inserting configuration, the flexible member  140  has a substantially convex configuration and can be inserted between adjacent stator portions  150 ,  151 . 
     Then, the screw  190  of the pre-tensioning tool  180  is untightened from the threaded hole  130  of the coupling portion  160  of the flexible member  140  such that the separate walls  181 ,  182  of the tool  180  move away from the flexible member until the operating configuration shown in  FIG. 3  is reached. In this configuration, the flexible member  140  is compressed by the stator portions  150 ,  151  and the winding coils  120 ,  121  so that it comes into contact with winding coils  120 ,  121 . 
     Finally, the pre-tensioning tool  180  is removed from the flexible member  140  once properly fitted between the adjacent stator portions  150 ,  151 . 
     In some cases, the pre-tensioning tool  180  could be left in the supporting device  100  with the screw  190  partially or totally unscrewed. This could be useful for example to adjust the degree of deformation of the flexible member  140  of the supporting device  100  over the time, if required. 
     Although only a number of particular examples of the present supporting device for supporting winding coils in a wind turbine generator have been disclosed herein, it will be understood by those skilled in the art that other alternative examples and/or uses and obvious modifications and equivalents thereof are possible. 
     For example, although the present supporting device has been described as suitable for wind turbine generators, the present supporting device may however be also applied to any other types of rotating electrical machines. Also, although the flexible member has been described in one example as a leaf spring made of a flexible and/or elastic material, other types of flexible members could be used as long as a suitable force is applied to the winding coils for retaining them in position in the stator core. 
     The present disclosure thus covers all possible combinations of the particular examples described and should not be limited by particular examples, but should be determined only by a fair reading of the claims that follow.