Patent Publication Number: US-10777348-B2

Title: Winding layer pitch compensation for an air-core reactor

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This is a U.S. national stage of application No. PCT/AT2014/050009 filed 14 Jan. 2014. Priority is claimed on Austrian Application No. 50179/2013 filed 15 Mar. 2013, the content of which is incorporated herein by reference in its entirety. 
     BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to a winding layer pitch compensation for an air-core reactor which has at least two concentric winding layers spaced apart radially from one another. 
     2. Description of the Related Art 
     Air-core reactors are used in energy supply networks and, by contrast with oil-insulated reactors, are “dry-insulated reactors”, in which the insulation is provided by solid insulation and sufficient air clearances and creepage distances and which as a rule also do not contain any ferromagnetic core, i.e., their central air space is free. 
     The concentric winding layers of the air-core reactor are each held at their upper and lower axial ends by a holder star, which is composed of a number of star-shaped arms disposed radially. Instead of a one-piece holder star, a plurality of individual star sheets can also be used in each case, which only lie in the area below and above the winding layers, in order to save on star sheet material. The holder stars or star sheets lying opposite one another are tensioned in relation to one another in such cases with the aid of spacer strips or tension bandages extending between the winding layers, in order to hold the winding layers. During winding of the reactor, the star sheets and spacer strips are simultaneously used as winding aids, in that the lower star sheets are initially tensioned on a turning device and the winding layers are then constructed thereon, where a set of spacer strips is installed between them in each case. 
     As a result of the different conductor cross sections in the individual winding layers different pitches and/or axial installation heights of the individual winding layers are produced in such cases, which require winding layer pitch compensation. Here, compensation sheets are inserted between the star sheets lying opposite one another axially and the winding layer lying between said sheets, which support the winding layers in relation to the star sheets and center them in an axial direction. 
     Conventional compensation sheets are relatively complex parts because the height to be compensated for between a star sheet and a winding layer varies depending on the circumferential location of the reactor, radial location of the winding layer and conductor cross-section of the winding layer, which even for a single coil dimensioning demands a plurality of different individually-calculated compensation sheets. For different coil dimensionings, the required variations in compensation sheets multiply. 
     SUMMARY OF THE INVENTION 
     In view of the foregoing, it is an object of the invention to overcome the disadvantages of the known solutions and to provide a simplified winding layer pitch compensation for air-core reactors. 
     These and other objects and advantages are achieved in accordance with the invention achieved by the combination of a first set of strip-shaped star sheets, which are each intended to be radially arranged below or above the winding layers and are provided along one edge with at least one receiving slot emanating from the edge, and a second set of strip-shaped compensation sheets, which are provided in each case along one edge with at least one insert slot emanating from the edge, where a compensation sheet is pushable into each receiving slot of a star sheet in a form fitting manner and the star sheet in this case engages in a form fitting manner into its insert slot, and where the slot depths of at least two receiving slots of the set of star sheets are different. 
     In accordance with the invention, a modular plug-in system is thus created for constructing winding layer pitch compensation from only a few variable parts, these being on the one hand compensation sheets and on the other hand star sheets, which based on the their slots are able to be slotted into one another to make a form fit, where the slot depths in the star sheets define the protrusion, i.e., effective compensation height of the compensation sheets. Through this the compensation sheets can be all designed uniformly, however, with different thicknesses corresponding to the conductor cross section as explained in greater detail below, and thus produced and stocked very simply in few variants. The slot depths of the star sheets can be simply pre-calculated and then the slots made to the corresponding depths, which represents a comparatively simple final production step and can be undertaken, for example, on uniform types of unslotted star sheet blanks. Overall, a mechanically highly-rigid system extremely variable in its dimensioning and compensation options is produced, which very much facilitates both the production and also the stockkeeping of the winding layer pitch compensation. 
     For single layer area reactor, cores star sheets can be used that have only a single receiving slot, where the slot depths of the receiving slot can then be different within the set of star sheets between different star sheets. For multilayer air core reactors, it is especially advantageous when each star sheet has at least two receiving slots spaced apart from one another emanating from the edge, of which the slot depths are different, so that different effective compensation heights for different layers can be created for each individual star sheet. 
     In accordance with a preferred embodiment of the invention, the star sheets are made of metal and the receiving slots are milled into the sheets. On the one hand, this fulfils the requirements for high rigidity of the star sheets which must carry the great weight of the winding layers and, on the other hand, this makes possible an overall rapid and highly precise final production of the star sheet blanks, e.g., by CNC milling to the desired slot depths. 
     Furthermore, it is especially useful if the compensation sheets including their insert slots are molded or cut from plastic. In this way, the compensation sheets can simultaneously exercise an insulator function and (just apart from different thicknesses for different conductor cross sections) can be manufactured essentially uniformly, e.g. by pre-molding the plastic. If glass reinforced plastic (GRP) is used as the plastic, the slots can also be made by cutting into the sheets, which can be performed with a uniform slot depth and thus lower production demands, e.g. manually with a single template. 
     As has already been briefly discussed, the slot widths of at least two receiving slots of a star sheet are preferably different and the compensation sheets preferably have correspondingly adapted different thicknesses to enable winding layers with different conductor cross-sections to be supported. 
     In an embodiment of the invention, a number of star sheets can be welded at their ends into a star, so that they form holder stars. As an alternative, the star sheets are preferably formed as “star sheet stump”, i.e., the star sheets in their installation position do not reach into the central air space of the air-core reactor, in order to save on material and weight. 
     In any event it is especially useful if, in accordance with further embodiments of the invention, the star sheets have anchorages for spacer strips or tension bandages running between the winding layers, e.g., holes for screwing on or suspending these types of elements. 
     Other objects and features of the present invention will become apparent from the following detailed description considered in conjunction with the accompanying drawings. It is to be understood, however, that the drawings are designed solely for purposes of illustration and not as a definition of the limits of the invention, for which reference should be made to the appended claims. It should be further understood that the drawings are not necessarily drawn to scale and that, unless otherwise indicated, they are merely intended to conceptually illustrate the structures and procedures described herein. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The invention will be explained in greater detail below on the basis of an exemplary embodiment presented in the enclosed drawings, in which: 
         FIG. 1  shows a perspective view of an air-core reactor with two different embodiments (one indicated by dashed lines) of a winding layer pitch compensation in accordance with the invention; 
         FIG. 2  shows a detailed perspective view of one of the star sheets of the winding layer pitch compensation of  FIG. 1  with inserted compensation sheets; and 
         FIGS. 3 and 4  each show a detailed perspective view of a star sheet and a compensation sheet. 
     
    
    
     DETAILED DESCRIPTION OF THE EXEMPLARY EMBODIMENTS 
     With reference to  FIG. 1 , an air-core reactor  1 , e.g., for high-voltage energy supply networks, has four concentric winding layers  2 ,  3 ,  4 ,  5 , which are spaced apart from one another by spacer strips  6  distributed around the circumference to form cooling air gaps  7  between them. In this case, each of the winding layers  2 ,  3 ,  4 ,  5  is formed from a plurality of windings of a conductor  9 , such as a wire, wire run or wire cable lying above one another in the axial direction  8  of the air-core reactor  1 , and reaches (depending on conductor cross section diameter D and number of windings) an individual winding layer height h 2 -h 5  (only h 5  of the outer layer  5  shown). 
     The winding layers  2 ,  3 ,  4 ,  5  are held together at their upper and lower axial ends  10 ,  11  by multi-arm holder stars  12 ,  13 , which are tensioned against one another by tensioning bands  14  and/or the spacer strips  6 . Here, each holder star  12 ,  13  is composed from a plurality of radially-disposed star sheets  15 , which are shown into forms of embodiment in  FIG. 1 . In the embodiment of  FIG. 1 , as shown with dashed extension lines, the star sheets  15  run into the center of the central air space  16  of the air-core reactor  1  and are welded together there at their ends  17 , if necessary forming a hub into the holder star  12 ,  13 . 
     In the version depicted by solid lines in  FIG. 1 , the star sheets  15  are shortened to “star sheet stumps”, which are only disposed in the area below or above the winding layers  2 ,  3 ,  4 ,  5 , so that they no longer extend into the central air space  16  of the air-core reactor  1 . 
     As a result of the different installation heights h 2 -h 5  of the different winding layers  2 ,  3 ,  4 ,  5 , a winding layer pitch compensation is required between the star sheets  15  and the winding layers  2 ,  3 ,  4 ,  5 , more precisely between their first and last windings of the conductor  9 , in order to hold each winding layer  2 ,  3 ,  4 ,  5  in a force fit between the respective star sheets  15  lying axially opposite one another. A plurality of individual compensation sheets  18  disposed in each case between a star sheet  15  and a winding layer  2 ,  3 ,  4 ,  5  are used for this, the interaction of which with the star sheets  15  will be explained in greater detail with reference to  FIGS. 2, 3, 4 . 
     In accordance with  FIGS. 2, 3, 4 , each star sheet  15  is strip shaped, e.g., in the form of an approximately rectangular small plate, and is provided along a longitudinal edge  19  with a number of receiving slots  20  emanating from the longitudinal edge  19 . The number of receiving slots  20  corresponds to the number of winding layers  2 ,  3 ,  4 ,  5  for which the star sheet  15  is intended. For its part, each compensation sheet  18  is strip shaped, e.g., in the form of an approximately rectangular small plate, and is provided with (at least) one insert slot  22  emanating from an edge  21 . 
     A compensation sheet  18  is now able to be inserted into each receiving slot  20  of a star sheet  15  in a form fitting manner such that the star sheet  15  simultaneously engages into the insert slot  22  of the compensation sheet  18  to make a form fit, as shown in  FIG. 2 . The compensation sheets  18  are thus inserted onto or into the star sheets  15  as a normal or transversely. The slot widths B S  of the receiving slots  20  of the star sheets  15  correspond in each case respectively to the thicknesses D A  of the compensation sheets  18  received therein and, vice versa, in accordance with the slot widths B A  of the slots  22  of the compensation sheets  18 , corresponds to the thicknesses D S  of the star sheets  15  inserted into them. 
     The star sheets  15  preferably have a uniform thickness D S , and correspondingly the slot widths B A  of the insert slots  22  are uniformly the same. The compensation sheets  18 , on the other hand, have different thicknesses D A , and these depend on the conductor cross section diameter D of the winding layer  2 ,  3 ,  4 ,  5  to be supported. Accordingly, the slot thicknesses B S  of the receiving slots  20  of the star sheets  15  are also different and are adapted to the thickness D A  of the compensation sheet  18  to be received in each case. 
     The slot thicknesses T A  of the insert slots  22  of the compensation sheets  18  are preferably (even if not necessarily) uniform. By contrast the slot depths T S  of the different receiving slots  20  of a star sheet  15  are different in each case, i.e., at least two slot depths T S  of two receiving slots  20  are different from one another. This means that the compensation sheets  18  penetrate to different depths into a star sheet  15  and thus create different effective compensation heights ah 2 , ah 3 , ah 4 , ah 5  (in  FIG. 2  only ah 5  is shown for the outermost layer  5 ) between a star sheet  15  and a winding layer  2 ,  3 ,  4 ,  5 . In such cases, star sheets  15  distributed over the circumference of air-core reactor  1  also have increasing or decreasing slot depths T S , in order to receive the rise of the conductor  9  of a winding layer  2 ,  3 ,  4 ,  5  in the course of the first or last winding. 
     The star sheets  15  are preferably made of metal, especially an aluminum alloy, and the receiving slots  20  therein are preferably made by milling, e.g., CNC milling. The compensation sheets  18  for the purposes of insulation are preferably made of plastic, e.g. glass reinforced plastic (GRP). The insert slots  22  in the compensation sheets  18  can be molded out at the same time during the production of the plastic compensation sheets  18  or can be cut, punched, milled etc. into them subsequently. Here, as a rule, only one uniform slot depth T A  and one uniform slot width B A  are required. As a result, the cutting in of the insert slots  22  can also be performed manually with the aid of a single template. 
     The star sheets  15  can be equipped with additional anchorages for the spacer strips  6 , such as a plurality of holes  23 , with which the spacer strips  6  can be screwed on. Further anchorages, such as holes  24 , can be provided for additional tension bandages (tension strips) with which the star sheets  15  lying axially opposite one another can be additionally tensioned. 
     In the production of the air-core reactor  1 , the star sheets  15  can be inserted, for example, into holders  25  that can be installed on the turning disk of a winding machine distributed over the circumference and then the compensation sheets  18  (or initially only the radially innermost compensation sheet  18 ) pushed onto them. After the winding of the first, innermost winding layer  2 , a set of spacer strips  6  is distributed over the circumference and screwed to the star sheets  18 , then the next compensation sheets  18  (provided this has not yet been done) are placed onto the star sheets  15 , then the next winding layer  3  is wound, etc. 
     It should be understood that in simple forms of embodiments for single-layer reactor cores, the star sheets  15  can each have only one single receiving slot  20 , where the receiving slots  20  of different star sheets  15  in a set of star sheets can have different slot depths T S , in order to receive the rise of the conductor  9  over the circumference of the air-core reactor  1 . 
     Thus, while there have been shown, described and pointed out fundamental novel features of the invention as applied to a preferred embodiment thereof, it will be understood that various omissions and substitutions and changes in the form and details of the devices illustrated, and in their operation, may be made by those skilled in the art without departing from the spirit of the invention. For example, it is expressly intended that all combinations of those elements and/or method steps which perform substantially the same function in substantially the same way to achieve the same results are within the scope of the invention. Moreover, it should be recognized that structures and/or elements shown and/or described in connection with any disclosed form or embodiment of the invention may be incorporated in any other disclosed or described or suggested form or embodiment as a general matter of design choice. It is the intention, therefore, to be limited only as indicated by the scope of the claims appended hereto.