Patent EA-001635-B1 (EA)
Title: A transformer/reactor and a method for its manufacturing
Inventor: LEIJON MATS
IPC: H01F27/28
Filed: 1998-02-02
Abstract: 1. A transformer/reactor comprising a core and at least one winding, in which the core (1; 11; 21; 31) consists of at least two segments (4; 14; 24, 25; 33, 34, 36, 37), and the winding is flexible and comprises an electrically conducting core (7) surrounded by an inner semiconducting layer (8), an insulating layer (9) surrounding the inner semiconducting layer and consisting of solid material, and an outer semiconducting layer (10) surrounding the insulating layer, said layers adhering to each other. 2. A transformer/reactor as claimed in claim 1, characterized in that said layers (8, 9, 10) consist of materials having such elasticity and with such a relation between the coefficients of thermal expansion of the materials that the changes in volume in the layers caused by temperature fluctuations during operation can be absorbed by the elasticity of the materials, the layers thus retaining their adhesion to each other upon the temperature fluctuations that occur during operation. 3. A transformer/reactor as claimed in claim 2, characterized in that the materials in said layers (8, 9, 10) have high elasticity, preferably with an E-modulus less than 500 MPa, most preferably less than 200 MPa. 4. A transformer/reactor as claimed in claim 3, characterized in that the coefficients of thermal expansion for the materials in said layers (8, 9, 10) are of substantially the same magnitude. 5. A transformer/reactor as claimed in claim 4, characterized in that the adhesion between the layers (8, 9, 10) is of at least the same magnitude as in the weakest of the materials. 6. A transformer/reactor as claimed in claim 1 or claim 2, characterized in that each of the semiconducting layers (8, 10) essentially constitutes one equipotential surface. 7. A transformer/reactor as claimed in any of claims 1-6, characterized in that the windings of the stator (4) consist of high-voltage cable (6). 8. A transformer/reactor as claimed in claim 7, characterized in that the high-voltage cable (6) has a diameter within the interval 20-250 mm and a conductor area within the interval 80-3000 mm<2>. 9. A transformer/reactor as claimed in any of the preceding claims, characterized in that the core (1; 11; 21) is substantially annular. 10. A transformer/reactor as claimed in claim 9, characterized in that the core (1; 11; 21) comprises a window (5; 15; 25) having substantially circular shape and that the annular shape of the core is circular. 11. A transformer/reactor as claimed in claim 9, characterized in that the core comprises a window which is substantially elliptical and that the annular shape of the core is elliptical. 12. A transformer/reactor as claimed in any of claims 1-8, characterized in that in that the core (31) comprises four segments, two straight segments (36, 37) and two segments (33, 34) shaped as ring halves, the two segments shaped as ring halves being joined together via the two straight segments. 13. A transformer/reactor as claimed in any of the preceding claims, characterized in that the core (1; 11; 21) has a substantially toroidal form. 14. A transformer/reactor as claimed in any of claims 1-8, characterized in that the core has a rectangular form. 15. A transformer/reactor as claimed in any of claims 1-11 or 13-14, characterized in that the core (21) consists of two segments (23, 24). 16. A transformer/reactor as claimed in any of the preceding claims, characterized in that each segment comprises a plurality of plates (3) and in that the core is constructed as a laminated core. 17. A transformer/reactor as claimed in claim 16, characterized in that the plates (3) consist of magnetically oriented steel. 18. A transformer/reactor as claimed in claim 17, characterized in that the number of segments is sufficiently large for the magnetic orientation direction not to be lost. 19. A transformer/reactor as claimed in claim 16, characterized in that the plates (3) consist of amorphous steel. 20. A transformer/reactor as claimed in any of claims 16-19, characterized in that the adjacent segments are held together by one segment having at least one protruding plate which is fitted into a corresponding gap between plates arranged in the corresponding side of the nearest adjacent segment, thereby forming an overlap joint. 21. A transformer/reactor as claimed in any of the preceding claims, characterized in that it comprises attachment devices, preferably clamps or screws in order to join the segments. 22. A transformer/reactor as claimed in any of the preceding claims, characterized in that the segmented core contains internal ducts (17) for a coolant. 23. A transformer/reactor as claimed in claim 22, characterized in that adjacent segments are held together by at least one segment being provided with a cooling duct (17) terminating in a protruding tube end designed to be fitted to a corresponding tube end terminating the cooling duct in an adjacent segment. 24. A transformer/reactor as claimed in any of the preceding claims, characterized the transformer is a dry transformer/reactor. 25. A method for use in the manufacturing of a transformer/reactor comprising a core and at least one winding, comprising the step of manufacturing a core including at least two segments which are joined to form said core, and comprising the step of installing a winding onto said core, said winding being flexible and composed of an electrically conducting core (7) surrounded by an inner semiconducting layer (8), an insulating layer (9) surrounding the inner semiconducting layer and consisting of solid material, and an outer semiconducting layer (10) surrounding the insulating layer, said layers adhering to each other. 26. A method as claimed in claim 25, characterized in that the windings of the core are wound onto the segment before the segment is assembled to form the core.