Patent Publication Number: US-7210218-B2

Title: Method for fabricating electrical core sheet assemblies

Description:
BACKGROUND OF THE INVENTION 
   Field of the Invention 
   The invention relates to a method for fabricating electrical core sheet assemblies such as transformer limbs, transformer yokes and transformer cores. The electrical core sheets, whose main surfaces have been provided with an anti-corrosion layer, are cut into the desired shape. 
   In transformer core fabrication, the electrical core sheets (also referred to as core plates) are customarily cut into the desired shape at the outset. The two main surfaces of the utilized core sheets are already provided with an anti-corrosion layer by the sheet manufacturer. Next, the cut core sheets are assembled so as to form the transformer limbs and the bottom transformer yoke. Next, the side surfaces of these transformer limbs and of the bottom transformer yoke must be provided with an anti-corrosion layer. The winding is then installed around the transformer limbs; that is to say, the transformer limbs are wrapped. In the next step, the cut core sheets of the top transformer yoke are mounted. The side surfaces of the top transformer yoke are then provided with an anti-corrosion layer. The final production of the transformer then occurs. 
   In that method, additional manual production steps are required for coating the side surfaces of the transformer limbs and the transformer yokes, in particular. 
   SUMMARY OF THE INVENTION 
   It is accordingly an object of the invention to provide a method for fabricating core sheet assemblies, which overcomes the above-mentioned disadvantages of the heretofore-known devices and methods of this general type and which is simplified in comparison with the prior methods for producing electrical core sheet assemblies. 
   With the foregoing and other objects in view there is provided, in accordance with the invention, a method of fabricating an electrical core sheet assembly, such as a transformer limb, a transformer yoke, or a transformer core. The method comprises the following method steps: 
   providing electrical core sheets with main surfaces having an anti-corrosion layer; 
   cutting the electrical core sheets into a desired shape to form cutting edges at lateral surfaces of the core sheets; 
   providing the cutting edges with an anti-corrosion layer; and 
   subsequently assembling the cut core sheets into the core sheet assembly. 
   In other words, the objects of the invention are achieved in that the side surfaces (that is to say, the cutting edges) of the cut core sheets are first provided with an anti-corrosion layer, and only then are the cut core sheets assembled into the desired core sheet assembly. 
   In accordance with an added feature of the invention, the anti-corrosion layer is applied by rolling, spreading, or spraying. 
   In accordance with a concomitant feature of the invention, a two-component epoxy resin system is used. 
   The advantages that can be achieved with the invention consist particularly in the simplification of the production of electrical core sheet assemblies by the providing of the all-round coating of cut core sheets prior to the assembling of the core sheet assembly, by virtue of the fact that fewer production steps are required overall. The coating process, i.e. the application of the anti-corrosion layer to the cutting edges, can be performed fully automatically, which improves the quality of the anti-corrosion layers compared to a manual coating technique. 
   Other features which are considered as characteristic for the invention are set forth in the appended claims. 
   Although the invention is illustrated and described herein as embodied in a method for fabricating electrical core sheet assemblies, it is nevertheless not intended to be limited to the details shown, since various modifications and structural changes may be made therein without departing from the spirit of the invention and within the scope and range of equivalents of the claims. 
   The construction and method of operation of the invention, however, together with additional objects and advantages thereof will be best understood from the following description of specific embodiments when read in connection with the accompanying drawing. 

   
     BRIEF DESCRIPTION OF THE DRAWING 
     The FIGURE is a sectional view of a section taken through a core sheet. 
   

   DESCRIPTION OF THE PREFERRED EMBODIMENTS 
   Referring now to the sole FIGURE of the drawing in detail, there is shown a cross-section of an electrical core sheet  1  that has been cut into a desired shape. The two main surfaces of the core sheet  1  have already been provided with anti-corrosion layers  2  and  3  at the manufacturer&#39;s. In addition, all lateral edges (i.e. cut edges) of the core sheet  1  are provided with anti-corrosion layers  4  and  5  following the cutting of the core sheet and before the assembly of several core sheets into a core sheet assembly. That is, each individual core sheet is provided with all-around corrosion protection. 
   In the fabrication of a core sheet assembly, particularly a transformer core, the electrical core sheets  1  are first cut into the desired shape. As described above, after the core sheets  1  are cut, all side edges (cutting edges) of the core sheets  1  are provided with anti-corrosion layers  4  and  5 . Next, the cut core sheets  1  are assembled, forming the transformer limbs and the bottom transformer yoke. The winding is then placed around the transformer limbs; i.e., the transformer limbs are wrapped. In the next step, the cut core sheets of the top transformer yoke are mounted. The final production of the transformer then occurs. 
   The coating of the cut edges of the core sheets is performed automatically immediately following the cutting of the core sheets in the core cutting apparatus, with the coating material being rolled, spread, or sprayed on. A two-component epoxy resin system with sufficient temperature resistance can be used as the coating material.