Transformer, assembly, and method for manufacturing a transformer

Abstract

The invention relates to a transformer comprising a core (2) having an outer core section (2.1) and an inner limb section (2.2), wherein the inner limb section (2.2) is at least partially surrounded around its circumference by the outer core section (2.1), wherein the inner limb section (2.2), or a heat-conducting element (3), or an insulating film which is arranged on the inner limb section (2.2), is directly wound to form a primary coil (4) and a secondary coil (5), wherein the outer core section (2.1) is formed by joining together a plurality of core sub-elements (2.1.1, 2.1.2, 2.1.3, 2.1.4), wherein at least some of the core sub-elements (2.1.1, 2.1.2, 2.1.3, 2.1.4) are joined to the exterior of the wound inner limb section (2.2) in such a way that some of the core sub-elements (2.1.1, 2.1.2, 2.1.3, 2.1.4), or at least one heat-conducting element (6), or an insulating film provided thereon, are in direct contact with the winding of the primary coil (4) and of the secondary coil (5).

Description

[0001] Transformer, assembly and method for producing a transformer

[0002] The invention relates to a transformer, an assembly comprising a transformer and a housing, and a method for producing a transformer.

[0003] The expansion of electromobility requires the construction of charging stations with one or more charging points where the batteries of electric vehicles can be charged with electrical energy. Such charging points should offer a compact design while simultaneously providing high charging power.

[0004] Charging stations, in particular, include a transformer to convert electrical power to a different current / voltage ratio. Such transformers are subjected to high electrical power, for example, up to 200 kW, so that despite the transformer's very high efficiency, considerable power loss occurs (e.g., at 99.9% efficiency and 200 kW power, 200 W of power loss occurs), which must be dissipated in the form of heat.

[0005] Transformers for charging stations are known in which the transformer's coil windings are mounted on a plastic coil former. This plastic coil former has one or more insertion openings into which, after the coil former has been wound, the core elements can be inserted to form the transformer's magnetic core. A disadvantage of this known transformer is its very complex structure. This complex structure is necessary, on the one hand, to dissipate the resulting waste heat and, on the other, to adjust the required main and stray inductance of the transformer.

[0006] Based on this, the object of the invention is to provide a transformer which enables good dissipation of the heat generated in the area of ​​the coil and, moreover, has a simple structure.

[0007] The object is achieved by a transformer having the features of independent patent claim 1. An assembly comprising a transformer and a housing is the subject of independent patent claim 17, and a method for producing a transformer is the subject of further independent patent claim 18. Preferred embodiments are the subject of the dependent claims.

[0008] According to a first aspect, a transformer is disclosed. The transformer comprises a core with an outer core section and an inner leg section. The inner leg section is at least partially encompassed circumferentially by the outer core section, so that the magnetic circuit is closed via the outer core section. A primary coil and a secondary coil are provided on the inner leg section. The inner leg section or a heat-conducting element arranged on the inner leg section or an insulating film arranged on the inner leg section is directly wound to form the primary coil and the secondary coil. The heat-conducting element can be formed by a heat-conducting film or a heat-conducting pad. The outer core section is formed by joining together several core sub-elements.At least some of the core sub-elements are attached to the outside of the wound inner leg section in such a way that at least this part of the core sub-elements or at least a heat-conducting element / insulating film provided thereon directly abuts the winding of the primary coil and the secondary coil. The wound inner leg section, for example, is initially formed as a separate core element, is wound directly as such, and is then integrally connected to the outer core section as a wound inner leg section, either directly or indirectly via an insulating element arranged therebetween.In other words, one or more core sub-elements, which are part of the outer core section, are attached to the outside of the primary coil and the secondary coil in such a way that the core sub-element is directly connected to the primary coil and the secondary coil, or indirectly connected via a heat-conducting element arranged therebetween. The heat-conducting element, which is provided between the coil winding and the core sub-element, can be formed by a heat-conducting foil or a heat-conducting pad.

[0009] The technical advantage of the transformer is that by directly winding the inner leg section and adding several core sub-elements to form the outer core section, a simple and cost-effective design of the transformer is achieved. The direct winding of the inner leg section has the advantage that there is good heat transfer on the inside of the coil between the winding of the primary coil and secondary coil and the inner leg section, allowing the heat to be dissipated via the inner leg section towards the housing. The external attachment of at least one core sub-element to the primary coil and secondary coil also ensures good heat transfer on the outside of the coil between the winding of the primary coil and secondary coil and the outer core section, allowing further heat to be dissipated to the housing via the outer core section.The formation of the outer core section from several core sub-elements has the technical advantage that these can be assembled without gaps among each other and also relative to the inner leg section in such a way that even with tolerances of the individual core sub-elements and / or the inner leg section, no air gap is created which leads to a deterioration of the inductive properties of the transformer and / or to a deteriorated heat transfer.

[0010] According to one exemplary embodiment, the outer core section has at least three cuboid-shaped or plate-shaped core sub-elements. The outer core section has a single outer leg formed by a first core sub-element that runs parallel to the inner leg section and is attached to the primary coil and the secondary coil on the outside, either directly or indirectly via a heat-conducting element. The connection between the first core sub-element and the inner leg section is formed by two further core sub-elements that are designed as yokes, run transversely, in particular perpendicularly, to the inner leg section and the outer leg, and connect the outer leg to the inner leg section on opposite sides. This results in a technically very simple and compact design of the transformer.

[0011] According to one embodiment, the outer core section is designed asymmetrically. A first core sub-element runs parallel to the inner leg section and is attached to the outside of the winding of the primary coil and the secondary coil on a first side. The winding of the primary coil and the secondary coil is exposed on a second side, which is opposite the first side, i.e. no core sub-element of the outer core section is provided on the second side. As a result, the primary coil and the secondary coil can be arranged on this second side directly or indirectly, for example via a heat-conducting element, on a wall of the housing, so that optimized heat dissipation towards the housing is achieved. The heat-conducting element can, for example, be a heat-conducting foil, a heat-conducting pad and / or a layer of potting material, wherein the layer thickness of the potting material is preferably less than 2 mm.

[0012] According to one exemplary embodiment, the core elements of the outer core section are joined to one another and / or to the inner leg section at abutments and are preferably integrally connected, in particular glued, there. The core elements and / or the inner leg section are designed and arranged relative to one another such that the abutment lines formed at the abutments immediately following one another in the circumferential direction each have an angle of 90° or substantially 90° to one another. This ensures that geometric tolerances of the core elements and / or the inner leg section can be compensated for by shifting the core elements relative to one another.This has the advantage that a core sub-element can always be arranged directly or at least indirectly via a heat-conducting element on the primary coil and the secondary coil and, despite tolerances of the inner leg section and the core sub-elements, the remaining core sub-elements can be positioned relative to one another and / or on the inner leg section in such a way that no undesirable air gaps arise that impair heat dissipation via the core and / or the inductive properties of the transformer. According to one exemplary embodiment, the outer core section forms a closed frame or box around the inner leg section wound with the primary coil and secondary coil. The inner leg section is arranged, for example, in an interior region of the outer core section and the outer core section encompasses the inner leg section circumferentially.This design allows for even heat dissipation from the primary and secondary coils to the core, both from the coil's interior through the inner leg section to the outside, and from both sides from the coil's exterior to the outer legs of the core. This allows for good heat dissipation despite the compact design.

[0013] According to one embodiment, the outer core section has at least four plate-shaped or cuboid-shaped core elements. At least four core elements can be used to form a frame- or box-like outer core section, the core elements of which each come into contact with a component in one spatial direction, for example, the free end of the inner leg section or the outer side of the primary and secondary coils, while still being able to be arranged relative to one another in a transverse, particularly perpendicular, direction such that no gap exists between the core elements and the inner leg section. This makes it possible to achieve a transformer with good heat dissipation and with low tolerances in the electrical properties.Regardless of their number, the plate-shaped or cuboid-shaped core elements have the technical advantage that the risk of core fractures is reduced due to their simple geometry. According to one embodiment, a first and a second plate-shaped or cuboid-shaped core element each run parallel to the inner leg section and rest on the outer side of the winding of the primary coil and the secondary coil, either directly or via a heat-conducting element. The first and second core elements thus form the outer legs of a shell-type transformer and ensure optimized heat dissipation to a housing in which the transformer can be housed.

[0014] According to one embodiment, a third and a fourth plate-shaped or cuboid-shaped core element each extend transversely to the inner leg section and are arranged so close to the inner leg section that the magnetic circuit is closed from the inner leg section to the outer core section. The third and fourth core elements can be located directly on the free end of the inner leg section or can be spaced from it by an insulating element. Preferably, the third and fourth core elements are located at least indirectly on the inner leg section without an air gap in order to ensure good heat transfer from the inner leg section to the third and fourth core elements.

[0015] According to one embodiment, the outer core section has at least one angularly shaped core sub-element, which is formed as a one-piece molded element. This allows the core to be formed from a reduced number of core sub-elements.

[0016] According to one embodiment, the core sub-elements of the outer core section, and preferably also the inner leg section, are bonded to the outer core section by adhesive bonding. This allows the individual core sub-elements to be firmly bonded to form a mechanically stable and manageable core.

[0017] According to one embodiment, the inner leg section has a circular, oval, polygonal, or polygonal cross-sectional shape with rounded corners. A circular cross-sectional shape results in the shortest wire length of the coil winding and thus reduced electrical loss. However, the cross-sectional shape can also be selected differently, particularly depending on the available installation space and the possible heat dissipation to the housing.

[0018] According to one embodiment, the inner leg section is formed from a plurality of inner leg core elements that are integrally connected. For example, the inner leg section can be formed from a plurality of plate-shaped inner leg core elements stacked on top of one another. Alternatively, the inner leg section can be formed from a plurality of inner leg core elements joined together in the longitudinal and transverse directions. This makes it possible, particularly with a ferrite core, to assemble the inner leg section from a plurality of cost-effectively producible inner leg core elements.

[0019] According to one embodiment, a spacer made of a thermally conductive material is provided between two immediately adjacent inner leg core elements. This allows the main inductance of the transformer to be adjusted.

[0020] According to one embodiment, the inner thigh

[0021] Core elements at least partially different

[0022] Cross-sectional dimensions. In particular, the inner leg section can be divided into two halves by an inner leg core element, which is provided at a distance from the free ends of the inner leg section. The primary coil can be provided on one half and the secondary coil on the other half. The leakage inductance of the transformer can be determined by the air gap that the inner leg core element, which has the enlarged cross-sectional dimension, forms with the outer legs of the outer core section.

[0023] According to one embodiment, the primary coil and secondary coil are formed by a bifilar coil winding.

[0024] According to another embodiment, the primary coil and the secondary coil are arranged at a distance from one another on the inner leg portion.

[0025] According to one embodiment, the primary coil and secondary coil have a maximum of two winding layers in the radial direction. This effectively prevents heat buildup inside the coil winding.

[0026] According to one embodiment, the winding of the primary coil and the secondary coil is formed by an RF stranded wire. This preferably comprises a plurality of individually insulated wires, which are surrounded by a common outer insulation on the outer circumference. This minimizes electrical losses occurring at high switching frequencies.

[0027] According to one embodiment, the core has a cover element that at least partially spans an opening formed by the outer core section and has an inner contour that is shaped to match the primary and / or secondary coil. The shaped inner contour can, for example, have a concave curvature or a raised portion that is shaped to match the outer contour of the primary and / or secondary coil. Thus, additional heat dissipation to a housing into which the transformer is installed can be achieved via the cover element.

[0028] According to one embodiment, the core is made of a ferrite material. This allows the electrical losses of the transformer to be reduced.

[0029] According to a further aspect, an assembly comprising a transformer and a housing with a housing interior is disclosed. The transformer is inserted into the housing interior and encapsulated in the housing using a potting material.

[0030] According to yet another aspect, a method for manufacturing a transformer is disclosed. The method comprises the following steps:

[0031] - Providing an inner leg section;

[0032] - Providing a plurality of core sub-elements to form an outer core section;

[0033] - producing a primary coil and a secondary coil by directly winding the inner leg portion, a heat-conducting element arranged on the inner leg portion, or an insulating film arranged on the inner leg portion with an electrical conductor;

[0034] - producing an outer core section extending at least partially circumferentially around the wound inner leg section by attaching the core sub-elements to the wound inner leg section in such a way that at least one core sub-element, at least one heat-conducting element provided thereon or at least one insulating film provided thereon bears directly against the winding of the primary coil and the secondary coil;

[0035] - Material connection of the core elements of the outer core section to each other.

[0036] “Thermally conductive” in the sense of the present disclosure means thermal conductivity coefficients X > 0.5 W / mK.

[0037] The terms “approximately”, “essentially” or “about” mean, in the sense of the invention, deviations from the exact value by + / - 10%, preferably by + / - 5% and / or deviations in the form of changes that are insignificant for the function.

[0038] Further developments, advantages, and possible applications of the invention will become apparent from the following description of exemplary embodiments and from the figures. All described and / or illustrated features, individually or in any combination, are fundamentally part of the invention, regardless of their summary in the claims or their reference back to them. The content of the claims is also incorporated into the description.

[0039] The invention is explained in more detail below with reference to several exemplary embodiments. They show:

[0040] Fig. 1 shows an example of a first embodiment of the transformer in a perspective side view; Fig. 2 shows an example of a sectional view of the transformer according to Fig. 1 along a sectional plane that includes the vertical central longitudinal axis of the inner leg section;

[0041] Fig. 3 shows, by way of example, a sectional view of the transformer according to Fig. 1 along a sectional plane which runs perpendicular to the vertical central longitudinal axis of the inner leg section;

[0042] Fig. 4 shows an example of a second embodiment of the transformer in a perspective side view;

[0043] Fig. 5 shows, by way of example, a sectional view of the transformer according to Fig. 4 along a sectional plane which runs perpendicular to the vertical central longitudinal axis of the inner leg section;

[0044] Fig. 6 shows an example of a third embodiment of the transformer in a perspective side view;

[0045] Fig. 7 shows, by way of example, a sectional view of the transformer according to Fig. 6 along a sectional plane which runs perpendicular to the vertical central longitudinal axis of the inner leg section;

[0046] Fig. 8 shows an example of a fourth embodiment of the transformer in a perspective side view;

[0047] Fig. 9 shows an example of a sectional view of the transformer according to Fig. 8 along a sectional plane that includes the vertical central longitudinal axis of the inner leg section; Fig. 10 shows an example of a sectional view of the transformer according to

[0048] Fig. 8 along a sectional plane perpendicular to the vertical central longitudinal axis of the inner leg section;

[0049] Fig. 11 shows an example of a fifth embodiment of the transformer in a perspective side view;

[0050] Fig. 12 shows an example of a sixth embodiment of the transformer in a side view;

[0051] Fig. 13 shows, by way of example, a sectional view of the transformer according to Fig. 12 along a sectional plane which includes the vertical central longitudinal axis of the inner leg section;

[0052] Fig. 14 shows, by way of example, a sectional view of the transformer according to Fig. 12 along a sectional plane which runs perpendicular to the vertical central longitudinal axis of the inner leg section; and

[0053] Fig. 15 is an exemplary and schematic block diagram illustrating the method steps of a method for manufacturing a transformer.

[0054] Figures 1 to 3 show a first embodiment of a transformer 1 in different representations. The transformer has a core 2, a primary coil 4, and a secondary coil 5.

[0055] The transformer 1 has a shell-type core 2. The primary coil 4 and the secondary coil 5 are provided on an inner leg section 2.2, and an outer core section 2.1 surrounds the wound inner leg section 2.2 on the outer circumference. The outer core section 2.1 has two outer legs running parallel to the inner leg section 2.2 and two yokes running transversely to the inner leg section 2.2 and the outer legs, creating a magnetic coupling between the inner leg section 2.2 and the outer legs. No winding is provided on the outer core section 2.1. In other words, the transformer 1 is designed as a shell-type transformer, i.e., the wound inner leg section 2.2 is completely enclosed by the outer core section 2.1.

[0056] The core 2 is composed of several individual core parts which, after assembly, are materially bonded to one another, in particular glued. The inner leg section 2.2 of the core 2 is straight and directly wound on the outer circumference. “Directly wound” means that the electrical conductor 8, which forms the winding of the primary coil 4 and secondary coil 5, is either wound directly onto the inner leg section 2.2 or that only a heat-conducting element 3 or an insulating film (i.e., electrically insulating film) is provided between the inner leg section 2.2. The heat-conducting element 3 can, for example, be formed by a heat-conducting film or a heat-conducting pad. In other words, there is no coil body, for example a plastic element which serves as a carrier for the primary coil 4 and / or secondary coil 5 and into which the core 2 is subsequently inserted. Due to the direct winding of the inner leg section 2.2, the heat dissipation from the primary coil 4 and secondary coil 5 to the inner leg section 2.2 of the core 2 can be improved.

[0057] As can be seen in Fig. 2, the primary coil 4 and secondary coil 5 can be formed by bifilar winding of the inner leg section 2.2. Alternatively, the primary coil 4 and the secondary coil 5 can be provided as spatially separated coils on the inner leg section 2.2, for example, the primary coil 4 at an upper region of the inner leg section 2.2 and the secondary coil 5 at a lower region of the inner leg section 2.2, as shown in Fig. 11.

[0058] After the direct winding of the inner leg section 2.2, several core sub-elements are attached to form the outer core section 2.1. In the illustrated embodiment, the outer core section 2.1 is formed from several plate-shaped core sub-elements 2.1.1, 2.1.2, 2.1.3, 2.1.4. The first and second core sub-elements 2.1.1,

[0059] 2.1.2 each forms an outer leg and runs with its longitudinal axis parallel to the longitudinal axis LA of the inner leg section 2.2. The first and second core sub-elements 2.1.1, 2.1.2 are each attached to the directly wound inner leg section 2.2 in such a way that the side surface facing the inner leg section 2.2 either rests directly on the coil winding of the primary coil 4 and the secondary coil 5 or on a heat-conducting element 6 that is provided between the coil winding of the primary coil 4 and the secondary coil 5 and the first and second core sub-elements 2.1.1, 2.1.2. The heat-conducting element 6 can be formed, for example, by a heat-conducting film or by a heat-conducting pad. This makes it possible to achieve improved heat dissipation from the primary coil 4 and the secondary coil 5 to the first and second core sub-elements 2.1.1, 2.1.2.

[0060] The outer core section 2.1 also has a third and a fourth core sub-element 2.1.3, 2.1.4, each of which is arranged with the longitudinal axis transverse, in particular perpendicular to the longitudinal axis LA of the inner leg section

[0061] 2.2. The third and fourth core sub-elements 2.1.3, 2.1.4 are arranged at a distance from one another, one in each case in the region of the two free ends of the inner leg section 2.2. The third and fourth core sub-elements 2.1.3, 2.1.4 each span the wound inner leg section 2.2 such that they come into contact with the first and second core sub-elements 2.1.1, 2.1.2.

[0062] In order to achieve a tolerance-independent contact of the inner leg section 2.2 on the third and fourth core sub-elements 2.1 .3, 2.1.4 and a contact of the first and second core sub-elements 2.1 .1 , 2.1 .2 on the third and fourth core sub-elements 2.1 .3, 2.1.4, the plate-shaped core sub-elements 2.1 .1 , 2.1 .2, 2.1 .3, 2.1 .4 are arranged such that the core sub-elements 2.1.1 , 2.1.2, 2.1.3, 2.1.4 each bear with a narrow side against a further core sub-element and at the opposite end region with the broad side against another, further core sub-element. In other words, the joining of the core sub-elements 2.1 .1 , 2.1 .2, 2.1 .3, 2.1 .4 takes place in such a way that the circumferentially successive butt lines SL, which form at the joints between adjacent core sub-elements 2.1 .1 , 2.1 .2, 2.1 .3, 2.1 .4, are each aligned perpendicular to one another.For example, the butt line SL, which forms between the first and third core sub-elements 2.1.1, 2.1.3, runs perpendicular to the circumferentially following butt line SL, which forms between the second and third core sub-elements 2.1.2, 2.1.3. Thus, despite length tolerances of the core sub-elements 2.1.1, 2.1.2, 2.1.3, 2.1.4, they can directly contact the primary coil 4 and the secondary coil 5, as well as the free ends of the inner leg section 2.2.

[0063] The heat generated in the area of ​​the primary coil 4 and the secondary coil 5 can, as shown by the arrows in Fig. 1, be dissipated either directly via the core sub-elements 2.1.1, 2.1.2, or outwards via the inner leg section 2.2 to the core sub-elements 2.1.3, 2.1.4. To increase the insulation strength of the transformer, an electrical insulator can be provided between the free ends of the inner leg section 2.2 and the core sub-elements 2.1.3, 2.1.4. However, this insulator is preferably designed to be thermally conductive in order to ensure the best possible heat dissipation from the inner leg section 2.2 to the third and fourth core sub-elements 2.1.3, 2.1.4, despite the insulating effect.

[0064] As can be seen in Fig. 3, the inner leg section 2.2 has a circular cross-sectional shape. This allows the wire length to be minimized.

[0065] The inner leg section 2.2 is preferably formed, as can be seen in Fig. 2, from a plurality of inner leg core elements 2.2.1 arranged as a stack, thereby forming the columnar inner leg section 2.2. The inner leg core elements 2.2.1 are preferably integrally connected to one another, in particular glued, in order to be firmly connected to one another, so that the inner leg section 2.2 (optionally with a heat-conducting element 3 extending circumferentially around the inner leg section 2.2) can be directly wound.

[0066] To set a desired main inductance of the transformer 1, a spacer 7 can be inserted between two consecutive inner leg core elements 2.2.1. The spacer 7 is made, for example, from a material with low magnetic conductivity. Thus, a gap can be created between two consecutive inner leg core elements 2.2.1 via the material thickness of the spacer 7. The width of the gap influences the main inductance. The spacer 7 is preferably made of a thermally conductive material to continue to ensure heat transport through the inner leg section 2.2.

[0067] As shown in the alternative embodiment of Fig. 11, one or more inner leg core elements 2.2.1 can have a larger cross-sectional dimension than the remaining inner leg core elements 2.2.1. In this case, the primary coil 4 and the secondary coil 5 are preferably provided on the inner leg section 2.2, separated by the larger-sized inner leg core elements 2.2.1. Between the side surfaces of the inner leg core element 2.2.1 facing the outer core section 2.1, which has a larger cross-sectional dimension, and the outer core section 2.1, air gaps are formed, which are dimensioned such that a predetermined leakage inductance of the transformer 1 is established.

[0068] Figures 4 to 5 and 6 to 7 show a second and a third embodiment of a transformer 1, respectively. Only the differences compared to the previously described embodiment will be explained below. Otherwise, the previous explanations also apply to these embodiments of the transformer 1.

[0069] The essential difference between the transformers 1 according to Figures 4, 5 and 6, 7 is that the inner leg section 2.2 has a cross-sectional shape that deviates from the circular shape.

[0070] For space reasons, it may be necessary to reduce the overall width of the transformer 1. In this case, the inner leg section 2.2 can, for example, have a polygonal or substantially polygonal cross-sectional shape, as is the case in the embodiment of the transformer 1 according to Figures 4 to 5. In particular, the inner leg section 2.2 can have an at least substantially square, rectangular, or a cross-sectional shape with more than four corner regions. To prevent damage to the insulation of the electrical conductor 8 of the primary and secondary coils 4, 5 due to the edges and an excessively small bending radius, the corner regions are preferably rounded.

[0071] Furthermore, alternatively, the inner leg section 2.2 can have an oval or substantially oval shape, as is the case in the exemplary embodiment according to Figures 6 and 7. "Oval or substantially oval shape" is understood here in particular to mean a rectangular basic shape with rounded corners, so that the narrow sides are semicircular or substantially semicircular in shape.

[0072] Figs. 8 to 10 show a further embodiment of a transformer 1 according to the invention. Only the differences compared to the previously described embodiments are explained below. Otherwise, the previous explanations also apply to this embodiment of the transformer 1 according to Figs. 8 to 10.

[0073] The essential difference between this embodiment and the previously described embodiments is that the outer core section 2.1 is asymmetrical to the wound

[0074] Inner leg section 2.2 is formed. The outer core section 2.1 has only a single outer leg, which is arranged on one side of the wound inner leg section 2.2. The core 2 therefore does not have a second outer leg that runs parallel to a first outer leg and to the inner leg section 2.2 and is arranged on the other side of the inner leg section 2.2 to form a symmetrical core 2. In other words, the outer core section 2.1 is not designed as a frame that circumferentially surrounds the wound inner leg section 2.2 arranged centrally in this outer core section 2.1.

[0075] In this exemplary embodiment, the outer core section 2.1 comprises at least two core sub-elements. In the exemplary embodiment shown, the outer core section 2.1 has three core sub-elements 2.1.1, 2.1.2, 2.1.3. The first core sub-element 2.1.1 is arranged as a plate- or block-like core sub-element parallel to the inner leg section 2.2 and is arranged on the directly wound inner leg section 2.2 in such a way that the inner side of the first core sub-element 2.1.1 facing the inner leg section 2.2 comes into contact with the primary coil 4 and secondary coil 5 either directly or via a heat-conducting element 6 arranged therebetween.

[0076] The second core sub-element 2.1.2 is arranged above the free end of the inner leg section 2.2 in such a way that, on the one hand, it rests with a first side surface, either directly or via a heat-conducting insulator, against the upper end face of the inner leg section 2.2, and on the other hand, it rests by means of a second side surface against a side face of the first core sub-element 2.1.1. In the same way, the third core sub-element 2.1.3 is arranged below the free end of the inner leg section 2.2 in such a way that, on the one hand, it rests with a first side surface, either directly or via a heat-conducting insulator, against the lower end face of the inner leg section 2.2, and on the other hand, it rests by means of a second side face against a side face of the first core sub-element 2.1.1.3, the magnetic circuit is closed on one side, and the heat generated by the current flow through the primary and secondary coils 4, 5 is dissipated through the core 2 toward a housing (not shown) that encloses the transformer 1 on the outside. On the other hand, the primary and secondary coils 4, 5 can be placed opposite a housing, for example, on the side opposite the first core sub-element 2.1.1, or very close to this housing, so that direct heat dissipation from the primary and secondary coils 4, 5 to the housing can occur.

[0077] Alternatively, the first core part element 2.1 .1 can be designed as an L-shaped molded part and thus replace the second or third core part elements 2.1.2, 2.1.3.

[0078] In the embodiment of Figs. 8 to 10, the inner leg section 2.2 preferably has a substantially square or substantially rectangular cross-section, as can be seen in particular in Fig. 10. Due to the large direct contact surface, the heat dissipation from the primary and secondary coils 4, 5 to the first core sub-element 2.1.1, on the one hand, and from the primary and secondary coils 4, 5 to the housing, on the other hand, can be improved.

[0079] Preferably, the transformer 1 has the following features regardless of the embodiment described above:

[0080] The electrical conductor 8, which forms the primary and secondary coils, is preferably a high-frequency stranded wire. This wire comprises a plurality of individual wires. The individual wires each have electrical insulation on the outside to electrically insulate the individual wires from one another. Furthermore, the individually insulated wires of the high-frequency stranded wire are surrounded by an outer insulation that electrically insulates the electrical conductor 8 on the outer circumference. The use of a high-frequency stranded wire reduces the electrical losses of the transformer 1.

[0081] The core 2, in particular the inner leg core elements 2.2.1 and the core elements 2.1.1, 2.1.2, 2.1.3, 2.1.4 of the outer core section 2.1, are formed from an electrically non-conductive ceramic material with high magnetic conductivity, in particular a ferrite. This allows the electrical losses of the transformer 1 to be reduced.

[0082] The transformer 1 is designed, in particular, as a charging station transformer, i.e., for use in a DC charging station. Such transformers are high-frequency power transformers that provide electrical power in the range from 5 kW to 200 kW, in particular between 25 kW and 100 kW, and are designed for switching frequencies in the range from 20 kHz to 150 kHz, in particular 40 kHz to 100 kHz.

[0083] The transformer 1 is preferably designed for electrical voltages in the range between 500V and 1000V and electrical currents up to 150Aeff.

[0084] As previously stated, the transformer 1 is designed to be inserted into a housing and encapsulated therein. The transformer 1 is cooled by heat transfer from the transformer 1 to the housing and subsequent heat dissipation from the housing. It should be noted that no cooling fluid is provided in the interior of the housing in which the transformer 1 is provided.

[0085] To ensure the best possible heat dissipation from transformer 1 to

[0086] To reach the housing, heat is dissipated via core 2 to the housing. Core 2, in particular the outer core section 2.1, is provided at least partially in close proximity to the housing's outer wall. "In close proximity" here means, in particular, distances of less than 2 mm.

[0087] In addition, the windings of the primary and secondary coils 4, 5 can also be partially routed to the system externally, either directly or indirectly via a heat-conducting element on the housing. This allows for direct heat dissipation from the primary and secondary coils 4, 5 to the housing.

[0088] The outer core section 2.1 can have a cover section which at least partially closes a lateral opening of the outer core section 2.1, as can be seen by way of example in Figures 1, 4 and 6. The cover section can be made of the same material as the outer core section, in particular of a ferrite. The cover section can have an inner contour which is adapted to the outer contour of the primary and secondary coils 4, 5. The cover section comes into contact with these either directly or via a heat-conducting element. On the outside, the cover section either lies directly against the housing or is provided in the immediate vicinity of the outer housing wall. “In the immediate vicinity” here means in particular distances of less than 2 mm.The inner contour of the cover section is adapted to the outer contour of the primary and secondary coils 4, 5, allowing improved heat dissipation from the primary and secondary coils 4, 5 to the housing.

[0089] Figs. 12 to 14 show a further embodiment of a transformer 1 according to the invention. Only the differences compared to the previously described embodiments are explained below. Otherwise, the previous explanations also apply to this embodiment of the transformer 1 according to Figs. 12 to 14.

[0090] The transformer 1 of Figures 12 to 14 is designed similarly to the embodiment of the transformer 1 according to Figures 8 to 10. The essential difference lies in the design of the inner leg section 2.2. The inner leg section 2.2 is also modular in this case, consisting of several rod- or block-shaped inner leg core elements 2.2.1 that are arranged next to one another as seen transversely to the longitudinal axis LA. For example, four rod- or block-shaped inner leg core elements 2.2.1 are joined together as a core element group in a layer of core elements aligned transversely to the longitudinal axis LA. The longitudinal axes of the inner leg core elements 2.2.1, along which the inner leg core elements 2.2.1 have the longest extension, are aligned parallel to the longitudinal axis LA of the inner leg section 2.2. The inner leg core elements 2.2.1 can have a length that is equal to or substantially equal to the length of the inner leg section 2.2.Alternatively, the inner leg section 2.2 can also be formed from several layers of inner leg core elements 2.2.1, viewed in the direction of the longitudinal axis LA, in the illustrated embodiment from two layers. A spacer 7 can be provided between the two layers. The spacer can be made of a thermally conductive material. The material thickness of the spacer 7 can be used to adjust the main inductance of the transformer 1. The inner leg core elements 2.2.1 are preferably integrally connected to one another.

[0091] A method for manufacturing a transformer 1 is described below with reference to Fig. 15. It should be noted that the steps of the method can be performed, at least in part, in a different order.

[0092] First, an inner leg section 2.2 is provided (S10). This provision can include assembling the inner leg section 2.2 from several inner leg core elements 2.2.1, which are integrally connected, in particular glued, to one another. The provided inner leg section 2.2 is rod-shaped or column-shaped and can therefore be wound directly.

[0093] In addition, several core sub-elements 2.1.1, 2.1.2, 2.1.3, 2.1.4 are provided, which are intended to form an outer core section 2.1 (S11). The core sub-elements 2.1.1, 2.1.2, 2.1.3, 2.1.4 are preferably cuboid-shaped and can be arranged relative to one another such that the outer core section 2.1 closes the magnetic circuit from one free end of the inner leg section 2.2 to the other end of the inner leg section 2.2.

[0094] Subsequently, a primary coil 4 and a secondary coil 5 are produced by directly winding the inner leg section 2.2 or a heat-conducting element 3 arranged on the inner leg section 2.2 with an electrical conductor 8 (S12). The primary coil 4 and the secondary coil 5 can be provided separately from one another on the inner leg section and spaced apart from one another. Alternatively, they can be interlocked by bifilamentary winding of the inner leg section 2.2.

[0095] After producing the wound inner leg section 2.2, the outer core section 2.1 is joined, which extends at least partially circumferentially around the inner leg section 2.2. The outer core section 2.1 is formed by attaching the core sub-elements 2.1.1, 2.1.2, 2.1.3, 2.1.4 to the wound inner leg section 2.2 such that at least one core sub-element 2.1.1, 2.1.2, 2.1.3, 2.1.4 or at least one heat-conducting element 6 provided thereon directly abuts the winding of the primary coil 4 and the secondary coil 5 (S13). The joining is carried out in such a way that the butt lines, which form at the joining points of the core elements 2.1.1, 2.1.2, 2.1.3, and 2.1.4, run at right angles to each other. This allows for the compensation of geometric tolerances inherent in the inner leg section 2.2 and the core elements 2.1.1, 2.1.2, 2.1.3, and 2.1.4.

[0096] Finally, the core elements of the outer core section 2.1 are joined, in particular glued, to one another (S14). Preferably, the inner leg section 2.2 is also glued to the outer core section 2.1 at the free end, so that the elements of the core 2 are firmly connected to one another.

[0097] To form an assembly, the transformer 1 is preferably placed inside a housing and encapsulated therein. The housing interior is adapted to the geometry of the transformer 1 in such a way that the outer core section 2.1 and, if applicable, a section of the primary coil 4 and the secondary coil 5 are arranged directly adjacent to and in direct contact with, or at a small distance from, the housing wall, preferably less than 5 mm. This allows for optimized heat dissipation of the heat generated in the area of ​​the coil windings via the core 2 to the housing and, if applicable, directly from the coil windings to the housing. One or more heat-conducting elements can be provided between the transformer 1 and the housing in order to improve heat dissipation from the transformer 1 to the housing. The invention has been described above using exemplary embodiments.It is understood that numerous changes and modifications are possible without departing from the scope of protection defined by the patent claims.

[0098] List of reference symbols

[0099] 1 transformer

[0100] 2 core

[0101] 2.1 outer core section

[0102] 2.1.1 first core subelement

[0103] 2.1.2 second core sub-element

[0104] 2.1.3 third core element

[0105] 2.1.4 fourth core element

[0106] 2.2 Inner leg section

[0107] 2.2.1 Inner leg core element

[0108] 3 Heat conducting element

[0109] 4 Primary coil

[0110] 5 Secondary coil

[0111] 6 Heat conducting element

[0112] 7 spacers

[0113] 8 electrical conductors

[0114] LA longitudinal axis

[0115] SL butt line

Claims

Patent claims 1) Transformer comprising a core (2) with an outer core section (2.1) and an inner leg section (2.2), wherein the inner leg section (2.2) is at least partially encompassed circumferentially by the outer core section (2.1), wherein the inner leg section (2.2), a heat-conducting element (3) or an insulating film, which are arranged on the inner leg section (2.2), are directly wound to form a primary coil (4) and a secondary coil (5), wherein the outer core section (2.1) is formed by joining together several core sub-elements (2.1.1, 2.1.2, 2.1.3, 2.1.4), wherein at least some of the core sub-elements (2.1.1, 2.1 .2, 2.1 .3, 2.1 .4) is attached on the outside to the wound inner leg section (2.2) in such a way that a part of the core sub-elements (2.1.1 , 2.1.2, 2.1.3, 2.1.4) or at least one heat-conducting element (6) provided thereon or an insulating film lie directly on the winding of the primary coil (4) and the secondary coil (5). 2) Transformer according to claim 1, characterized in that the outer core section (2.1) has at least three cuboid-shaped or plate-shaped core sub-elements (2.1.1, 2.1.2, 2.1.3, 2.1.4). 3) Transformer according to claim 1 or 2, characterized in that the outer core section (2.1) is designed asymmetrically and a core part element (2.1.1) runs parallel to the inner leg section (2.2) and is attached on a first side to the outside of the winding of the primary coil (4) and the secondary coil (5) and that the winding of the primary coil (4) and the secondary coil (5) is exposed on a second side, which is opposite the first side. 4) Transformer according to claim 1 or 2, characterized in that the outer core section (2.1) forms a closed frame or box around the inner leg section (2.2) wound with the primary coil (4) and secondary coil (5). 5) Transformer according to claim 4, characterized in that a first and a second cuboid-shaped core part element (2.1.1, 2.1.2) each run parallel to the inner leg section (2.2) and rest on the outside of the winding of the primary coil (4) and the secondary coil (5) directly or by means of a heat-conducting element (6) or an insulating film. 6) Transformer according to claim 4 or 5, characterized in that a third and a fourth plate-shaped core part element (2.1.3, 2.1.4) each run transversely to the inner leg section (2.2) and are arranged on the inner leg section (2.2) in such a way that the magnetic circuit is closed from the inner leg section (2.2) to the outer core section (2.1). 7) Transformer according to claim 1, 3 or 4, characterized in that the outer core section (2.1) has at least one angularly formed core part element which is designed as a one-piece shaped element. 8) Transformer according to one of the preceding claims, characterized in that the core sub-elements (2.1 .1 , 2.1 .2, 2.1 .3, 2.1 .4) of the outer core section (2.1 ) are connected to one another by gluing. 9) Transformer according to one of the preceding claims, characterized in that the inner leg section (2.2) has a circular, oval, polygonal or polygonal with rounded corners cross-sectional shape. 10) Transformer according to one of the preceding claims, characterized in that the inner leg section (2.2) is formed from several inner leg core elements (2.2.1) which are integrally connected. 11) Transformer according to claim 10, characterized in that a spacer (7) made of a heat-conducting material is provided between two immediately consecutive inner leg core elements (2.2.1). 12) Transformer according to claim 10 or 11, characterized in that the inner leg core elements (2.2.1) have at least partially different cross-sectional dimensions. 13) Transformer according to one of the preceding claims, characterized in that the primary coil (4) and secondary coil (5) are formed by a bifilar coil winding or that the primary coil (4) and the secondary coil (5) are arranged at a distance from one another on the inner leg section (2.2). 14) Transformer according to one of the preceding claims, characterized in that the winding of the primary coil (4) and the secondary coil (5) is formed by an RF stranded wire. 15) Transformer according to one of the preceding claims, characterized in that the core (2) has a cover element which at least partially forms a cover element through the outer core section (2.1). formed opening and has an inner contour adapted to the shape of the primary and / or secondary coil (4, 5). 16) Transformer according to one of the preceding claims, characterized in that the core (2) is formed from a ferrite material. 17) Assembly comprising a transformer (1) according to one of the preceding claims and a housing with a housing interior, wherein the transformer (1) is introduced into the housing interior and is potted in the housing by means of a potting material. 18) Method for producing a transformer (1) comprising the following steps: - providing an inner leg section (2.2) (S10); - Providing a plurality of core sub-elements (2.1.1, 2.1.2, 2.1.3, 2.1.4) to form an outer core section (2.1) (S11); - producing a primary coil (4) and a secondary coil (5) by directly winding the inner leg section (2.2), a heat-conducting element (3) or an insulating film arranged on the inner leg section (2.2) with an electrical conductor (8) (S12); - producing an outer core section (2.1) extending at least partially circumferentially around the wound inner leg section (2.2) by attaching the core sub-elements (2.1.1, 2.1.2, 2.1.3, 2.1.4) to the wound inner leg section (2.2) in such a way that at least one core sub-element (2.1.1, 2.1.2, 2.1.3, 2.1.4), at least one heat-conducting element (6) provided thereon or an insulating film directly is applied to the winding of the primary coil (4) and the secondary coil (5) (S13); - Material connection of the core elements (2.1 .1 , 2.1 .2, 2.1.3, 2.1.4) of the outer core section (2.1) among themselves (S14).

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