Transformer

Abstract

The invention relates to a transformer (1), in particular a medium frequency transformer, comprising a transformer core (2) with several core legs (4) which are connected to each other via yokes (3), and at least two conductor arrangements (5, 6) which are arranged around at least one of the core legs (4), characterized in that each conductor arrangement (5, 6) is designed as a stack of sheet metal lamellae with a plurality of sheet metal lamellae (7) arranged one above the other in a stacking direction.

Description

[0001] The invention relates to a transformer, in particular a medium-frequency transformer, comprising a transformer core with a plurality of core limbs connected to one another via yokes, and at least two conductor arrangements arranged around at least one of the core limbs. In particular, the invention relates to a medium-frequency transformer designed for frequencies from 100 Hz to several 1 kHz.

[0002] Transformers are known in the state of the art in a wide variety of designs. It is also known to reduce the size of transformers and design them for higher frequencies. For example, medium-frequency transformers require a transformer core with core limbs of significantly smaller cross-sections for comparable power transmission compared to conventional transformers operating at the usual mains frequency of 50 Hz. However, this does not apply to the conductors of the conductor arrangements designed as windings, which must transmit the load current. Accordingly, winding a winding wire with a comparatively large cross-section around a core limb with a comparatively small cross-section poses manufacturing problems.

[0003] Based on this prior art, it is an object of the present invention to provide a transformer of the type mentioned at the outset with an alternative structure.

[0004] To achieve this object, the present invention provides a transformer, in particular a medium-frequency transformer, comprising a transformer core with a plurality of core limbs connected to one another via yokes, and at least two conductor arrangements arranged around at least one of the core limbs, characterized in that each conductor arrangement is designed as a lamination stack with a plurality of laminations arranged one above the other in a stacking direction, which laminations can be made in particular of copper or aluminum. Thanks to this structure, the conductor arrangements can be manufactured by stacking individual laminations around the associated core limb, thus eliminating the traditional winding process and significantly simplifying production, particularly with comparatively small core limb cross-sections, as occur in medium-frequency transformers.

[0005] According to one embodiment of the present invention, the sheet metal laminations have an electrically insulating coating, for example a thin layer of lacquer or enamel, in order to prevent a short circuit.

[0006] Preferably, the laminations are each U-shaped, which allows them to be stacked around the associated core leg particularly easily and in a space-saving manner. In particular, the laminations are stacked in such a way that at least one stack formed from the main laminations also has a U-shape when the core leg is viewed from above.

[0007] Advantageously, the laminations are each formed from a plurality of lamination strips arranged adjacent to one another in a direction transverse to the stacking direction and preferably U-shaped. Thanks to the slots then present between adjacent lamination strips of a lamination, eddy current losses can be reduced.

[0008] The lamination stack of at least one conductor arrangement preferably has main laminations and counter laminations that are electrically connected to one another, the counter laminations being shorter than the main laminations. The main laminations are each guided around the associated core leg, while the counter laminations are positioned such that they are not interlinked with the magnetic flux through the transformer core. By providing such counter laminations, eddy current losses can be reduced and stray inductances can be adjusted. Furthermore, several adjacent main laminations can be electrically connected to one another via counter laminations such that these main laminations are electrically connected in series across the stack depth and are traversed by current in the same direction, which allows the length of the conductor to be adjusted.Thus, the main laminations of the high-voltage conductor arrangement are advantageously connected in series via counter laminations, in particular all main laminations of the high-voltage conductor arrangement.

[0009] In at least one conductor arrangement, in particular in the low-voltage conductor arrangement, sheet metal laminations, in particular all main sheet metal laminations, are electrically connected in parallel in the stacking direction.

[0010] According to one embodiment of the present invention, the transformer is characterized in that the transformer core has at least three adjacently arranged core legs, that at least two high-voltage windings and at least two low-voltage windings are arranged on the central transformer core leg, that the at least two high-voltage windings are positioned between the low-voltage windings, and that the laminations of the high-voltage winding are connected in series in the stacking direction and laminations of the low-voltage windings, in particular all laminations of the low-voltage windings, are connected in parallel in the stacking direction.

[0011] Further advantages and features of the present invention will become apparent from the following description with reference to the accompanying drawings. Fig. 1 is a sectional schematic plan view of a transformer according to an embodiment of the present invention; Fig. 2 a sectional schematic side view of the Fig. 1 transformer shown; Fig. 3 a schematic perspective exploded view of a portion of a transformer winding of the Fig. 1 shown transformer; and Fig. 4 is a sectional schematic plan view of a main lamination according to another embodiment of the present invention.

[0012] The Fig. 1 to 3 show a transformer 1 according to an embodiment of the present invention or components thereof. The transformer 1 is a medium-frequency transformer that can be designed for frequencies from 100 Hz to several 1 kHz. It comprises a laminated transformer core 2 made of steel with three core limbs 4 connected via yokes 3, wherein the cross-section of the middle core limb 4 is selected to be twice as large as the cross-section of the two outer core limbs 4. The transformer 1 also comprises four conductor assemblies 5, 6, which are arranged one above the other around the middle core limb 4 and are insulated in the direction of the transformer core 2, for example by insulating sleeves (not shown in detail). The two middle conductor assemblies 5 serve as high-voltage conductor assemblies, and the two outer conductor assemblies 6 serve as low-voltage conductor assemblies.Each conductor arrangement 5, 6 is provided as a lamination stack with a plurality of U-shaped laminations 7 arranged one above the other in a stacking direction. In this case, these laminations are made of copper or aluminum and provided with an electrically insulating coating, for example, made of lacquer or enamel. The laminations 7 of the high-voltage conductor arrangements 5 are electrically connected in series, and the laminations 7 of the low-voltage conductor arrangements 6 are connected in parallel. As shown in FIG. Fig. 3, for the technical implementation of the series connection, each of the U-shaped main laminations 7.1 and counter laminations 7.2 is provided, wherein the length of the counter laminations 7.2 is selected to be less than the length of the main laminations 7.1. Each counter lamination 7.2 is electrically connected at one of its free ends to the main lamination 7.1 arranged above it and at the other free end to the main lamination 7.1 arranged below it, for which purpose corresponding contact surfaces 8 are formed on the main and counter laminations 7.1 and 7.2, wherein the downwardly facing contact surfaces 8 in Fig. 3 are shown hatched. Accordingly, the counter plate slats 7.2, as shown in Fig. 3, indicated by arrows 9, converts the current flow during transformer operation without interlinking it with the core flux, resulting in current flowing through all main laminations 7.1 in the same direction. Furthermore, the counter laminations 7.2 reduce the leakage flux between the two main arms of the main laminations 7.1. This also allows the leakage inductance to be controlled over the length of the counter laminations 7.2. Eddy current losses are also reduced.

[0013] It should be noted that the illustrated circuit of high-voltage and low-voltage conductor arrangements 5, 6 can also be multiplied. Furthermore, a different arrangement of the high-voltage and low-voltage conductor arrangements 5, 6 can also be selected. Furthermore, counter-lamination laminations 7.2 can also be provided in a suitable manner for the low-voltage conductor arrangements 6 in order to adjust the stray inductance and / or reduce eddy current losses and / or vary the length of the main laminations 7.1 connected in parallel.

[0014] Fig.Figure 4 shows a variant according to the invention in which the laminations 7 are each formed from a plurality of lamination strips 10 arranged adjacent to one another in a direction transverse to the stacking direction. Thanks to the slots then present between adjacent lamination strips 10 of a lamination 7, eddy current losses can be reduced. Counter lamination strips (not shown in detail) can also be arranged between the lamination strips 10 to achieve the effects described above.

[0015] Although the invention has been illustrated and described in detail by the preferred embodiment, the invention is not limited by the disclosed examples, and other variations may be derived therefrom by those skilled in the art without departing from the scope of the invention. Thus, the transformer core can be designed as a toroidal core and also have two core limbs, around each of which one or more conductor arrangements are arranged, thereby dividing the current flow. Transformer cores with more than three core limbs are also conceivable.

[0016] Regardless of the grammatical gender of a particular term, persons with male, female or other gender identities are included.

Claims

[1] Transformer (1), in particular a medium-frequency transformer, comprising a transformer core (2) with a plurality of core limbs (4) which are connected to one another via yokes (3), and at least two conductor arrangements (5, 6) which are arranged around at least one of the core limbs (4), characterized by that each conductor arrangement (5, 6) is designed as a lamination stack with a plurality of laminations (7) arranged one above the other in a stacking direction. [2] Transformer (1) according to claim 1, characterized by that the sheet metal laminations (7) have an electrically insulating coating. [3] Transformer (1) according to claim 1 or 2, characterized by that the sheet metal slats (7) are each U-shaped. [4] Transformer (1) according to one of the preceding claims, characterized bythat the sheet metal laminations (7) are each formed from a plurality of sheet metal lamination strips (10) which are arranged adjacent to one another in a direction transverse to the stacking direction and are preferably U-shaped. [5] Transformer (1) according to one of the preceding claims, characterized by in that the lamination stack of at least one conductor arrangement (5, 6) has main laminations (7.1) and counter laminations (7.2) which are electrically connected to one another, the counter laminations (7.2) having a shorter length than the main laminations (7.1). [6] Transformer (1) according to one of the preceding claims, characterized by that in at least one conductor arrangement (6) sheet metal laminations are electrically connected in parallel in the stacking direction. [7] Transformer (1) according to one of the preceding claims, characterized bythat the transformer core (2) has at least three adjacently arranged core limbs (4), that at least two high-voltage windings (5) and at least two low-voltage windings (6) are arranged on the central core limb (4), that the at least two high-voltage windings (5) are positioned between the low-voltage windings (6), and that the laminations (7.1) of the high-voltage winding (5) are connected in series in the stacking direction and laminations (7.1) of the low-voltage windings (6), in particular all laminations (7.1) of the low-voltage windings (6) are connected in parallel in the stacking direction.

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