Transformer

Abstract

The invention relates to a transformer (1). The transformer (1) comprises two low-voltage windings (3, 5) and one high-voltage winding (7), wherein the two low-voltage windings (3, 5) are wound interleaved.

Description

The invention relates to a transformer, in particular a transformer for a wind turbine.With the transformer of a wind turbine, the electrical voltage generated by a generator of the wind turbine is adapted to a rated voltage of a power supply network, into which the electrical energy generated by the wind turbine is fed. The transformer receives an output voltage of a converter of the wind turbine as the primary voltage. The converter adjusts a frequency of a voltage of a generator of the wind turbine to a grid frequency of the energy supply grid. In this case, the converter is intended to compensate for the greatest possible amount of reactive power in order to maintain the grid stability, with the smallest possible short-circuit current of the transformer at the same time.The invention is based on the object of specifying a transformer which enables a converter of a wind turbine to compensate for the greatest possible amount of reactive power.The object is achieved according to the invention by a transformer having the features of claim 1.Advantageous embodiments of the invention are the subject matter of the dependent claims.A transformer according to the invention comprisestwo low-voltage windings anda high-voltage winding, whereinthe two low-voltage windings are wound in an interleaved manner.In a transformer according to the invention, the low-voltage winding is therefore divided into two low-voltage windings in comparison with a conventional transformer. As a result, the reactive power compensation by the converter of the wind turbine can be advantageously increased compared to a transformer with only one low-voltage winding. Furthermore, the low-voltage windings are interleaved instead of being wound geometrically separately from one another, as for example in so-called dual-pole transformers. This results in the two low-voltage windings generating a leakage flux that is similar to that of a single winding with the same total current. This leads to very similar impedances and thus a very similar short-circuit current of the transformer with the two low-voltage windings as in a transformer with only one low-voltage winding. A transformer according to the invention having two low-voltage windings which are wound in an interleaved manner in relation to one another therefore makes it possible to increase the reactive power compensation with an unchanged short-circuit current of the transformer, substantially with respect to a low-voltage winding.In one embodiment of the invention, the transformer has a transformer core, wherein the low-voltage windings and the high-voltage winding are wound around the transformer core. The transformer core amplifies and concentrates the magnetic field of the transformer.In a further embodiment of the invention, each low-voltage winding is a foil winding with a conductor foil wound around a winding axis, and the conductor foils of the two low-voltage windings are wound around the winding axis in a manner lying one on top of the other. The conductor foil of each low voltage winding is, for example, an aluminum foil or a copper foil. The conductor foils of the two low-voltage windings are electrically insulated from one another. By winding the conductor foils lying one on top of the other about the winding axis, the conductor foils follow one another alternately radially with respect to the winding axis. The formation of the conductor foils as aluminum foils or copper foils enables a high electrical conductivity of the low-voltage windings.In an alternative embodiment of the invention to the aforementioned embodiment, each low-voltage winding has a conductor running as a helix around a winding axis, and the helices formed by the conductors of the two low-voltage windings form a double helix. The conductor of each low-voltage winding is, for example, a twisted conductor. Furthermore, the conductors of the two low-voltage windings are manufactured, for example, from copper or aluminum. The conductors of the two low-voltage windings thus each form a helix running about the winding axis, wherein these two helices are offset relative to one another parallel to the winding axis. Twisted conductors have many individual conductors which are insulated from one another. This embodiment of the conductors advantageously reduces eddy current losses in the conductors compared to solid conductors which have the same cross-sectional area as the twisted conductors. The manufacture of the conductors from copper or aluminum enables a high electrical conductivity of the low-voltage windings.In a further embodiment of the invention, the high-voltage winding is wound around the low-voltage windings. For example, high-voltage winding has a conductor which is a round conductor or a flat conductor or a twisted conductor. This embodiment of the invention takes into account that the low-voltage winding generally has fewer turns and thicker conductors than the high-voltage winding and, owing to the higher voltage, requires better insulation than the low-voltage windings. By winding the high voltage winding around the low voltage windings, the isolation of the high voltage winding can be used to improve overall isolation of the transformer. Further, by disposing the high voltage winding on the outside of the transformer, the size and weight thereof can be reduced and the heat dissipation efficiency of the transformer can be improved.A wind turbine according to the invention has a transformer designed according to the invention.The above-described properties, features and advantages of this invention and the manner in which these are achieved become clearer and more clearly comprehensible in conjunction with the following description of exemplary embodiments, which are explained in more detail in conjunction with the drawings. The following are shown: FIG. 1 shows a first sectional illustration of a first exemplary embodiment of a transformer according to the invention, FIG. 2 shows a second sectional illustration of the transformer shown in FIG. 1, FIG. 3 shows a side view of a second exemplary embodiment of a transformer according to the invention, FIG. 4 shows a block diagram of an exemplary embodiment of a wind turbine according to the invention.Corresponding parts are provided with the same reference numerals in the figures.FIGS. 1 (1 ) and 2 (2 ) show a first exemplary embodiment of a transformer 1 according to the invention. The transformer 1 comprises two low-voltage windings 3, 5, a high-voltage winding 7 and a transformer core 9. FIG. 1 shows the transformer 1 in a schematic first sectional illustration in a first sectional plane. FIG. 2 shows the transformer 1 in a schematic second sectional illustration in a second sectional plane which is orthogonal to the sectional plane of FIG. 1, wherein the high-voltage winding 7 is not illustrated in FIG. 2.The low voltage windings 3, 5 and the high voltage winding 7 are wound around the transformer core 9. The transformer core 9 is formed from electric sheets 11 which are electrically insulated from one another and are arranged parallel to one another. A longitudinal axis of the transformer core 9 forms a winding axis 12 around which the low-voltage windings 3, 5 and the high-voltage winding 7 are wound.Each low-voltage winding 3, 5 is a foil winding with a conductor foil 13, 15 wound around the winding axis 12, The conductor foils 13, 15 of the two low-voltage windings 3, 5 are wound around the winding axis 12 in a manner lying one on top of the other and electrically insulated from one another. Each conductor foil 13, 15 is, for example, a copper foil or an aluminum foil.The high voltage winding 7 is wound around the low voltage windings 3, 5. The high-voltage winding 7 is thus at a greater distance from the winding axis 12 and from the transformer core 9 than the low-voltage windings 3, 5.FIG. 3 (FIG. 3 ) shows a second exemplary embodiment of a transformer 1 according to the invention. the transformer 1 in turn comprises two low-voltage windings 3, 5, a high-voltage winding 7 and a transformer core 9, wherein the high-voltage winding 7 is not illustrated in FIG. 3.The low voltage windings 3, 5 and the high voltage winding 7 are wound around the transformer core 9. The transformer core 9 is formed from electric sheets 11 which are electrically insulated from one another and are arranged parallel to one another. A longitudinal axis of the transformer core 9 forms a winding axis 12 around which the low-voltage windings 3, 5 and the high-voltage winding 7 are wound.Each low-voltage winding 3, 5 has a conductor 17, 19 running as a helix around the winding axis 12. The helices formed by the conductors 17, 19 of the two low-voltage windings 3, 5 form a double helix. The conductor 17, 19 of each low-voltage winding 3, 5 is, for example, a twisted conductor, the individual conductors of which are each manufactured, for example, from copper or aluminum.The high-voltage winding 7, not shown in FIG. 3, is wound around the low-voltage windings 3, 5. The high-voltage winding 7 is thus at a greater distance from the winding axis 12 and from the transformer core 9 than the low-voltage windings 3, 5.FIG. 4 (FIG. 4 ) shows a block diagram of an exemplary embodiment of a wind turbine 21 according to the invention. the wind turbine 21 comprises a generator 23, an inverter 25 and a transformer 1 according to the invention. the generator 23 is configured to convert the rotations of a rotor of the generator 23 generated by wind force into electrical energy. The inverter 25 is configured to adjust a frequency of an electric voltage generated by the generator 23 to a frequency of a power supply network to which the electric power generated by the wind turbine 21 is input. The transformer 1 is configured to adapt the voltage to a rated voltage of the energy supply network.The transformer 1 is designed like a transformer described with reference to FIGS. 1, 2 to 3.Although the invention has been illustrated and described in more detail by preferred exemplary embodiments, the invention is not restricted by the disclosed examples and other variations can be derived therefrom by the person skilled in the art without departing from the scope of protection of the invention.

Claims

Transformer (1) comprising - two low-voltage windings (3, 5) and - one high-voltage winding (7), wherein - the two low-voltage windings (3, 5) are wound in an interleaved manner.Transformer (1) according to Claim 1, having a transformer core (9), the low-voltage windings (3, 5) and the high-voltage winding (7) being wound around the transformer core (9).Transformer (1) according to Claim 1 or 2, wherein each low-voltage winding (3, 5) is a foil winding having a conductor foil (13, 15) wound around a winding axis (12), and the conductor foils (13, 15) of the two low-voltage windings (3, 5) are wound around the winding axis (12) in a manner lying one on top of the other.Transformer (1) according to claim 3, wherein the conductor foil (13, 15) of each low voltage winding (3, 5) is an aluminium foil or a copper foil.Transformer (1) according to Claim 1 or 2, wherein each low-voltage winding (3, 5) has a conductor (17, 19) running as a helix around a winding axis (12), and the helices formed by the conductors (17, 19) of the two low-voltage windings (3, 5) form a double helix.Transformer (1) according to claim 5, wherein the conductor (17, 19) of each low voltage winding (3, 5) is a twisted conductor.Transformer (1) according to Claim 5 or 6, wherein the conductors (17, 19) of the two low-voltage windings (3, 5) are manufactured from copper or aluminium.Transformer (1) according to one of the preceding claims, wherein the high-voltage winding (7) is wound around the low-voltage windings (3, 5).Transformer (1) according to one of the preceding claims, wherein the high-voltage winding (7) has a conductor which is a round conductor or a flat conductor or a twisted conductor.Wind turbine (21) having a transformer (1) designed according to one of the preceding claims.

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