Transformer unit, method for producing a transformer unit, and use of a transformer unit

Abstract

The invention illustrates and describes a transformer unit (1) for a power electronics converter (49), having a winding unit (3) having a primary winding (5) and a secondary winding (7), a magnetic core (9) arranged at least partially in the winding unit (3), a primary connection (15) for a high-voltage potential, said connection being arranged at a first end (11) of the winding unit (3) and being connected to the primary winding (5), and the magnetic core (9) being able to be connected to a low-voltage potential, wherein a conductive shielding electrode (19) is arranged in the region of the first end (11) and of the magnetic core (9) in such a way that the shielding electrode (19) can be brought to a high-voltage potential and in the process an at least predominantly homogeneous field can be generated between the shielding electrode (19) and the magnetic core (9). The invention furthermore illustrates and describes a method (100) for producing a transformer unit (1) for a power electronics converter (49) and to the use of a transformer unit (1) for a power electronics converter (49).

Description

[0001] Transformer unit, method for manufacturing a transformer unit and use of a transformer unit

[0002] The present invention relates to a transformer unit for a power electronic converter, a method for manufacturing a transformer unit for a power electronic converter and a use of a transformer unit for a power electronic converter.

[0003] Transformer units are known from the prior art and are used in established power electronic converters, such as solid-state transformers (SSTs). Established power electronic converters are used in modern electrical distribution and transmission systems, as well as in the integration of renewable energy sources and their use in smart grids.

[0004] The known power electronic converters comprise a high-voltage unit, a transformer unit, and a low-voltage unit. The high-voltage unit converts the incoming high voltage into an intermediate stage suitable for the transformer unit. Power electronic components, including switching elements such as IGBT or MOSFET transistors, are used to handle the high voltages efficiently and safely. The transformer unit provides galvanic isolation and voltage matching between the high-voltage and low-voltage units. It transforms the voltage from the intermediate stage of the high-voltage unit to the required level of the low-voltage unit. The low-voltage unit then converts the transformed voltage into the required output voltage. The low-voltage unit also uses power electronic components to regulate and stabilize the output voltage.This ensures that the output power meets the requirements of the connected loads.

[0005] In the context of the power electronic converters mentioned earlier, high voltage refers to voltage levels significantly higher than those typically found in conventional low-voltage systems, for example, around 20 kV, as used in solid-state transformers (SSTs). These voltage ranges are also frequently referred to as medium voltage. Such a voltage level is typical for applications in electrical power transmission and distribution, where high voltages are necessary for the efficient transmission of energy over long distances.

[0006] To convert the aforementioned voltage levels as efficiently as possible, known transformer units comprise a winding unit with a primary and a secondary winding and a magnetic core arranged within it. The primary winding is connected to a primary terminal of the transformer unit, and the secondary winding is connected to a secondary terminal of the transformer unit. It is particularly important that no flashovers occur within the transformer unit between the high voltage and the low voltage or the magnetic core.

[0007] To ensure safety, conventional transformer units feature an epoxy resin winding core, which, due to its insulating properties, reduces the risk of flashovers. Nevertheless, there is a risk of flashovers occurring when high voltage is connected to the primary winding. This can happen if the insulation is not adequately dimensioned or if field peaks occur that exceed the dielectric strength of the material. Flashovers can be caused by insufficient insulation, humid environmental conditions, or impurities that reduce the dielectric strength of the insulating materials. Such flashovers lead to short circuits and can cause serious damage to the transformer unit, as well as compromise the safety of the overall system, such as the safety storage system (SST).

[0008] In general, it is desirable in transformer units to distribute the load on the insulating materials evenly and to minimize the risk of field peaks that could lead to flashovers.

[0009] It is therefore an object of the present invention to provide a transformer unit in which the load on the insulating materials is evenly distributed and the risk of field peaks that could lead to flashovers is minimized. According to a first aspect of the invention, this object is achieved by a transformer unit for a power electronic converter with the features of claim 1. The transformer unit comprises a winding unit with a primary winding and a secondary winding and a magnetic core arranged at least partially within the winding unit. The transformer unit has a primary connection for a high-voltage potential arranged at a first end of the winding unit and connected to the primary winding. The magnetic core can be connected to a low-voltage potential.A conductive shielding electrode is arranged in the area of ​​the first end and the magnetic core in such a way that the shielding electrode can be brought to a high voltage potential and an at least predominantly homogeneous field can be generated between the shielding electrode and the magnetic core.

[0010] According to a second aspect of the invention, the aforementioned problem is solved by a transformer unit for a power electronic converter with the features of claim 2. The transformer unit comprises a winding unit with a primary winding and a secondary winding and a magnetic core arranged at least partially within the winding unit. The transformer unit has a secondary connection for a low-voltage potential, arranged at a second end of the winding unit and connected to the secondary winding. The magnetic core can be connected to a high-voltage potential. A conductive shielding electrode is arranged in the region of the second end and the magnetic core such that the shielding electrode can be brought to a low-voltage potential, thereby generating an at least predominantly homogeneous field between the shielding electrode and the magnetic core.

[0011] The transformer unit according to the second aspect of the invention differs from the transformer unit according to the first aspect in that the magnetic core is now located at high voltage potential instead of low voltage potential. In this case, the shielding electrode is arranged in the region of the second end, i.e., in the region of the secondary terminal.

[0012] The transformer unit is explained in more detail below, primarily according to the first aspect, with the explanations applying analogously to the transformer unit according to the second aspect. This applies in particular to identical or similar structural features of the two aspects.

[0013] The transformer unit comprises a winding assembly with a primary winding and a secondary winding, and a magnetic core at least partially integrated within the winding assembly. The winding assembly of the transformer unit can consist of, or be constructed with, the primary and secondary windings, both of which may be embedded in a polymer. The polymer may be a synthetic resin, such as an epoxy resin mixture. The primary and secondary windings are arranged such that a common magnetic core can pass through both windings, allowing the primary and secondary windings and the magnetic core together to form the basic structure of the transformer unit. The polymer can serve as a mechanical stabilizer.Furthermore, the polymer can also serve as an insulating material, protecting the primary and secondary windings from moisture, contaminants, and / or electrical flashovers. After embedding in the polymer, the winding unit can be cured, forming a solid, compact, and / or resistant body capable of withstanding the electrical and mechanical stresses encountered during the transformer unit's operation.

[0014] The winding unit has at least one recess extending through the primary and secondary windings. The winding unit is therefore open at both ends, allowing the magnetic core to be positioned within it. The winding unit can thus have a free space at both ends through which the magnetic core can be inserted. The magnetic core can be inserted into the winding unit by inserting two or four U-shaped half-shells from each side. The magnetic core can be divided transversely, creating two U-shaped half-shells that form an upper and a lower part of the magnetic core. These two parts can then be further divided longitudinally, resulting in a magnetic core consisting of a total of four U-shaped half-shells.These U-shaped half-shells can be positioned within the winding unit to close the magnetic circuit and achieve (ideally good) magnetic coupling between the primary and secondary windings. The U-shaped half-shells are specifically designed to ensure a uniform distribution of magnetic flux and / or to maximize the overall performance and / or efficiency of the transformer unit.

[0015] The transformer unit has a primary terminal for a high-voltage potential located at a first end of the winding unit and connected to the primary winding. The primary winding of the winding unit, which may comprise a primary winding and a secondary winding embedded in a polymer, can be designed such that the primary winding exits the winding unit at its first end. This can be advantageously achieved by (specially) insulated connecting wires or cables branching off from the ends of the primary winding and passing through the insulating polymer material. Brass bushings, for example, can be used for the primary terminal, which can also be referred to as the high-voltage terminal, and which serves to connect the high voltage to the primary winding. Inside the winding unit, the primary winding or a strand of the primary winding can be connected to the primary terminal.Outside the winding unit, a cable can be connected to the primary terminal to establish a connection to a high-voltage unit or other electrical components. The primary terminal itself can be equipped with (suitable) terminals or connectors that enable the simplest and / or safest possible connection to the high-voltage unit.

[0016] Particularly in transformer units for power electronic converters, it is especially advantageous, due to limited installation space, to route the primary connection at one end of the transformer unit in a direction parallel to the winding axis of the primary winding. Since power electronic converters, such as the power electronic converter cells of an SST, in which the transformer units described here can be used, are typically relatively flat, the transformer unit itself can also advantageously have a flat design or low height. An object is considered "flat" here, in particular, if its height is less than half its length and / or width.Therefore, the primary winding can be advantageously routed to the primary terminal of the transformer unit at the first end, and the secondary winding to the secondary terminal at the second end. This allows for a particularly flat design of the transformer unit. Furthermore, this has the advantage of providing an insulating gap between the primary and secondary terminals, and thus also between the high and low voltages.

[0017] The magnetic core can be connected to a low-voltage potential. "Low-voltage potential" can also mean that the magnetic core is grounded, thus bringing it to earth potential. Through the grounded magnetic core, potential voltages that may arise through induction or malfunction can be safely dissipated to earth. This has the advantage of reducing the risk of electrical flashovers. However, the low-voltage potential is not limited to earth potential.

[0018] A conductive shielding electrode is positioned in the region of the first end and the magnetic core such that the shielding electrode can be brought to a high-voltage potential, thereby generating at least a predominantly homogeneous field between the shielding electrode and the magnetic core. At the exit point of the primary terminal or on wires connected to the primary terminal, high electric field strengths can occur when the primary terminal is connected to a high voltage. These high field strengths, especially with insufficient electrical insulation and therefore inadequate potential reduction, can increase the risk of partial discharges, flashovers, or breakdowns.

[0019] As mentioned previously, the winding unit is open at both ends to facilitate the insertion of the magnetic core. Consequently, the transformer unit has a section, particularly between the magnetic core and the first end, where no insulating material is present. In this area, there is an increased risk of partial discharges, as high electric field strengths can occur at the primary terminal, which is at high voltage, and these field strengths can only be dissipated to a limited extent over the short air path. The risk of partial discharges can be significantly reduced by the shielding electrode, as a homogeneous electric field helps to distribute the electric field strengths more evenly and prevent local field peaks. Partial discharges typically occur at points with particularly strong concentrated electric fields, so-called field peaks, which exceed the dielectric strength of the insulating material.This is particularly true for areas where the electric field passes through materials with a low dielectric constant, such as air. A homogeneous field can contribute to a more uniform distribution of electric field strengths and / or minimize voltage differences between the primary terminal and the magnetic core. This can advantageously increase the overall insulation strength of the transformer unit and / or reduce the probability of partial discharges that could lead to flashovers or breakdowns.

[0020] In summary, it can be stated that a transformer unit is provided in which the load on the insulating materials is advantageously distributed more evenly and / or the risk of field peaks that could lead to flashovers is minimized.

[0021] In one embodiment, the shielding electrode is arranged at least partially along the electric field between the first or second end and the magnetic core. By arranging the shielding electrode between the first or second end and the magnetic core, a homogeneous electric field can be generated in the free space through which the magnetic core is guided, thereby reducing the risk of partial discharges and / or field spikes. The arrangement along the electric field is understood to mean, in particular, any arrangement of the shielding electrode that can generate a field that is as homogeneous as possible between the primary terminal and the magnetic core.

[0022] In one embodiment, the winding unit comprises an insulating material, and the primary and secondary windings are embedded in this insulating material. The insulating material can be a polymer, for example, an epoxy resin mixture. This polymer advantageously offers particularly high electrical insulation properties, which can make it possible to isolate large voltage differences between the primary and secondary windings and / or reduce electric fields. By embedding the primary and secondary windings in the polymer, the risk of flashovers and / or partial discharges can be reduced, especially since the polymer can distribute the electric field strengths evenly in the area of ​​the windings and / or prevent concentrated field peaks. This can contribute to improving the safety and / or reliability of the transformer unit.

[0023] In one embodiment, the transformer unit has a first termination unit arranged at its first end, with the shielding electrode being located on the first termination unit. The first termination unit can serve to close the winding unit and / or to close the space between the magnetic core and the winding unit. This allows the transformer unit to be closed at its first end, preventing the magnetic core from being led out of the winding unit, which can contribute to a more robust transformer unit.

[0024] In one embodiment, the transformer unit has a second termination unit arranged at its second end, with the shielding electrode being located on this second termination unit. The second termination unit can serve to terminate the winding unit and / or close the space between the magnetic core and the winding unit. This allows for a transformer unit with an enclosed space, which improves electrical insulation and / or reduces the risk of field strength concentrations. This enclosed space can help ensure or improve the stability of the electric fields within the transformer unit, further reducing the risk of partial discharges and / or flashovers. The second termination unit can also advantageously contribute to increasing mechanical stability and / or protecting the transformer unit from contamination.

[0025] In one embodiment, the first or second termination unit has a connection on a side opposite the shielding electrode for connecting the high-voltage potential or the low-voltage potential. This connection allows the shielding electrode to be connected to the high-voltage potential or the low-voltage potential in a particularly simple manner, especially through the space enclosed by the first and second termination units. This advantageously results in a particularly simple connection of the shielding electrode to the high-voltage or low-voltage potential. In particular, this makes it especially easy to use and connect the transformer unit in a power electronic converter.

[0026] In one embodiment, the shielding electrode has an arc-shaped cross-section. An arc-shaped cross-section here means, in particular, that the shielding electrode has a rounded and / or curved shape in its cross-sectional view, preferably without sharp corners and / or edges. An arc-shaped cross-section can be circular, oval, teardrop-shaped, parabolic, or kidney-shaped. The arc-shaped cross-section advantageously reduces the risk of locally increased electric field strengths that can arise from sharp edges. High field strengths caused by edges or corners can lead to flashovers or corona discharges, which can impair both the efficiency and the safety of the transformer unit.The arc-shaped cross-section advantageously allows the electric field to be distributed more evenly and / or reduces or even prevents the maximization of field strength at specific points. This advantageously contributes to a homogenized field distribution between two potentials, for example, the primary connection at high voltage and the magnetic core at low voltage.

[0027] Preferably, the shielding electrode has a torus shape with an elliptical longitudinal section. This means, in particular, that the shielding electrode is tubular, similar to a bent tube. The torus shape can therefore have an elongated, especially oval or oval-like, shape in plan view. This has the particular advantage that the elliptical geometry enables the most efficient possible distribution of the electric field to the magnetic core. Furthermore, the torus shape allows for a robust design and / or effective heat dissipation, which can increase the operational reliability and performance of the shielding electrode.In one embodiment, the shielding electrode extends along a yoke of the magnetic core and has a first width that corresponds to at least 50%, preferably at least 60%, more preferably at least 80%, and more preferably 100%, of a second width of the yoke of the magnetic core. The first width of the shielding electrode and the second width of the yoke are understood to be the extent in the front view of the magnetic core, viewed from the front. This means that the first and second widths are considered along a line passing through a front face of the yoke and a front face of the shielding electrode. This first and second width, or coverage, of the shielding electrode relative to the yoke allows for generous coverage of the yoke by the shielding electrode, thereby achieving a field that is as homogeneous as possible along the second width of the yoke.

[0028] In one embodiment, the shielding electrode extends in a direction perpendicular to the primary terminal and has a first width that corresponds to at least 100%, preferably at least 120%, and more preferably at least 150%, of a third width of the primary terminal. The primary terminal has at least two connections. The direction of extension of the primary terminal is understood to be the third width, from one end of a first connection to the other end of a second connection. Thus, the third width of the primary terminal is understood to be the extent of the connections. The first width of the shielding electrode relative to the primary terminal allows the shielding electrode to cover the primary terminal, thereby achieving a field that is as homogeneous as possible along the third width of the primary terminal.

[0029] As previously mentioned, the transformer unit can be used in a power electronic converter. Such a power electronic converter can be, for example, a single-phase transformer (SST) or a cell of an SST. A cell of an SST can comprise a high-voltage unit, a low-voltage unit, and the transformer unit described here. The transformer unit is positioned between the high-voltage unit and the low-voltage unit. The cell can have a frame or chambers with cell walls in which the high-voltage unit, the transformer unit, and the low-voltage unit are arranged. In one embodiment, the shielding electrode can be formed by a cell wall of the frame or chamber of the power electronic converter cell. For example, the shielding electrode can be formed by a cell wall of the high-voltage unit.This is particularly advantageous because the cell wall of the high-voltage unit is already at a high-voltage potential. Furthermore, in this embodiment, a separate component for the shielding electrode is not required, allowing the transformer unit to have a lower material density.

[0030] According to a third aspect of the invention, the aforementioned problem is solved by a method for manufacturing a transformer unit for a power electronic converter with the features of claim 11. The method comprises the following steps: providing a winding unit, a magnetic core, and a shielding electrode. The winding unit has a primary terminal or secondary terminal connected at a first end to the primary or secondary winding. Inserting the magnetic core into the winding unit. Attaching the shielding electrode in a region of the first end of the winding unit and the magnetic core, wherein the shielding electrode can be brought to a high-voltage potential or a low-voltage potential, thereby generating an at least predominantly homogeneous field between the shielding electrode and the magnetic core.In particular, the process can be carried out to manufacture a transformer unit described here.

[0031] The winding unit has a primary or secondary connection at a first end, connected to either the primary or secondary winding. The winding unit, magnetic core, and shielding electrode can be the winding unit, magnetic core, and shielding electrode described herein. In particular, the winding unit has a primary and secondary winding embedded in a cured polymer. The magnetic core has, in particular, at least two U-shaped half-shells, preferably four U-shaped half-shells, such that the magnetic core can have half-shells divided in both the longitudinal and transverse directions. The shielding electrode can be provided as a separate component and connected to the winding unit.This has the advantage that a modular design of the transformer unit can be achieved, in which the winding unit, the magnetic core and the shielding electrode can be interchangeable.

[0032] The method involves inserting the magnetic core into the winding unit. The winding unit has at least one recess extending through the primary and secondary windings. As mentioned previously, the winding unit is open at both ends to allow the magnetic core to be positioned within it. Therefore, the winding unit can have a free space at each end through which the magnetic core can be inserted. The magnetic core can be inserted into the winding unit by inserting two or four U-shaped half-shells into the winding unit from each side. These U-shaped half-shells can be positioned to close the magnetic circuit and / or provide magnetic coupling between the primary and secondary windings.The U-shaped half-shells can be designed to enable the most uniform distribution of magnetic flux possible and / or to improve the overall performance and / or efficiency of the transformer unit.

[0033] Preferably, the method involves joining parts of the magnetic core, preferably with an adhesive, before the magnetic core is inserted. This means, in particular, that if the magnetic core consists of several parts, for example, four U-shaped half-shells, at least some of these U-shaped half-shells are joined or bonded together before being inserted into the winding unit. This applies especially to two U-shaped half-shells that form an upper or lower half of the magnetic core. These two U-shaped half-shells can be joined together, preferably bonded, before insertion into the winding unit, creating two U-shaped half-shell units, each of which can be inserted into the winding unit through one end.

[0034] Bonding the U-shaped half-shells serves primarily to improve the structural integrity of the magnetic core and to firmly connect them, thus advantageously forming a stable unit comprising the winding assembly and the magnetic core. Bonding the U-shaped half-shells ensures that the magnetic core retains its shape during operation and does not fall apart or shift. The adhesive can also help to fill any gaps between the half-shells, thereby improving the magnetic properties of the core. Furthermore, the adhesive can contribute to improved heat dissipation and increase the mechanical strength of the entire transformer assembly.

[0035] The method further comprises attaching the shielding electrode in a region of the first end of the winding unit and the magnetic core, wherein the shielding electrode can be brought to a high-voltage potential or a low-voltage potential, thereby generating an at least predominantly homogeneous field between the shielding electrode and the magnetic core. "Attaching" refers in particular to positioning the shielding electrode relative to the magnetic core and / or relative to the primary and / or secondary terminals. The shielding electrode can be connected to and / or positioned relative to the winding unit, the primary terminal, the secondary terminal, or the magnetic core. Fastening means can be provided for this purpose, with which the shielding electrode can be attached to the winding unit, the primary terminal, the secondary terminal, and / or the magnetic core.This allows for particularly precise positioning of the shielding electrode, so that a field that is as homogeneous as possible can be generated between the shielding electrode and the magnetic core.

[0036] In one embodiment, the method comprises the following steps: Connecting the magnetic core to one potential derived from the high-voltage potential and the low-voltage potential. Connecting the shielding electrode to the other potential derived from the high-voltage potential and the low-voltage potential. Thus, the shielding electrode is always brought to, or connected to, a potential different from that of the magnetic core. This allows for the creation of a (unambiguous) electrical path or a field that is as homogeneous as possible between the two potentials, thereby reducing the risk of electrical arcing between the potentials, particularly in areas where the electric field passes through regions of materials with a low dielectric constant, such as air.In one embodiment, when the shielding electrode is located at the first end, it is connected to a high-voltage potential and the magnetic core to a low-voltage potential. Conversely, when the shielding electrode is located at the second end, it can be connected to a low-voltage potential and the magnetic core to a high-voltage potential. The transformer unit has primary and secondary terminals at both the first and second ends. These terminals can include connection sockets that are connected to the primary and secondary windings. Depending on the shielding electrode's position, the shielding electrode and the magnetic core can be brought to their respective potentials or connected to their respective voltage levels.The shielding electrode can be attached to either the first or second end and thus positioned between the magnetic core and the primary or secondary terminal. Typically, the primary terminal is connected to a high-voltage potential and the secondary terminal to a low-voltage potential. The magnetic core can be connected to either the high-voltage or the low-voltage potential. Therefore, the magnetic core and the shielding electrode can be connected according to the method described here, depending on the arrangement of the shielding electrode. This has the advantage that the shielding electrode does not require a fixed position, and the transformer unit can be connected depending on the arrangement of the shielding electrode.

[0037] According to a fourth aspect of the invention, the aforementioned problem is solved by using a transformer unit described herein for a power electronic converter with the features of claim 13. Accordingly, when the shielding electrode is arranged at the first end, the shielding electrode is connected to a high-voltage potential and the magnetic core to a low-voltage potential, and when the shielding electrode is arranged at the second end, the shielding electrode is connected to a low-voltage potential and the magnetic core to a high-voltage potential.

[0038] Further features, advantages, and applications of the present invention will become apparent from the following description of the embodiments and the figures. All features described and / or illustrated, individually and in any combination, constitute the subject matter of the invention, irrespective of their composition in the individual claims or their cross-references. In the figures, the same reference numerals denote identical or similar objects.

[0039] Figure 1 shows a schematic partial representation of an embodiment of a transformer unit,

[0040] Figure 2 shows another schematic partial representation of the transformer unit from Figure 1 ,

[0041] Figure 3 shows a schematic representation of an electric field of a transformer unit, as known from the prior art.

[0042] Figures 4a and 4b show schematic representations of the electric field of the transformer unit from Figures 1 and 2.

[0043] Figure 5 shows a schematic representation of a power electronic converter with the transformer unit from Figures 1 and 2, and

[0044] Figure 6 shows a flowchart of a process for manufacturing a transformer unit.

[0045] Figure 1 shows a schematic partial representation of an embodiment of a transformer unit 1. The transformer unit 1 has a winding unit 3 with a primary winding 5 and a secondary winding 7 (not shown in Fig. 1) and a magnetic core 9 arranged at least partially within the winding unit 3. The winding unit 3 of the transformer unit 1 can consist of the primary winding 5 and the secondary winding 7, both of which are embedded in a polymer. The polymer can be a synthetic resin, such as an epoxy resin mixture. The primary and secondary windings 5, 7 are arranged such that the magnetic core 9 can pass through both windings, so that the primary and secondary windings 5, 7 and the magnetic core 9 together form the basic structure of the transformer unit 1.The polymer can serve not only as a mechanical stabilizer but also as an insulating material, protecting the primary and secondary windings 5, 7 from moisture, impurities, and electrical flashovers. After being embedded in the polymer, the winding unit 3 is cured, forming a solid, compact, and resistant structure capable of withstanding the electrical and mechanical stresses during the operation of the transformer unit 1.

[0046] The transformer unit 1 has a first end 11 and a second end 13. At the first end 11 of the winding unit 3, a primary terminal 15 is arranged, which is connected to the primary winding 5. The primary terminal 15 is intended for connection to a high-voltage potential. At the second end 13 of the winding unit 3, a secondary terminal 17 is arranged, which is connected to the secondary winding 7. The secondary terminal 17 is intended for connection to a low-voltage potential. The magnetic core 9 can be connected to a low-voltage potential or to ground potential.

[0047] In the present embodiment, a conductive shielding electrode 19 is arranged at the first end 11 in the region of the first end 11 and the magnetic core 9 such that the shielding electrode 19 can be brought to a high voltage potential and an at least predominantly homogeneous field can be generated between the shielding electrode 19 and the magnetic core 9.

[0048] In an alternative embodiment not shown, the magnetic core 9 can be connected to a high-voltage potential. At the second end 13, a conductive shielding electrode 19 is arranged in the region of the second end 13 and the magnetic core 9 such that the shielding electrode 19 can be brought to a low-voltage potential, thereby generating at least a predominantly homogeneous field between the shielding electrode 19 and the magnetic core 9.

[0049] The transformer unit 1 according to the alternative embodiment differs from the transformer unit 1 according to the present embodiment in that the magnetic core 9 is located at high voltage potential instead of low voltage potential. In this case, the shielding electrode 19 is arranged in the region of the second end 13. The transformer unit 1 according to the present embodiment is explained in more detail below, with the explanations applying analogously to the transformer unit 1 according to the alternative embodiment. This applies in particular to identical or similar structural features of the two embodiments.

[0050] As shown in Figure 1, the transformer unit 1 has a first termination unit 21 arranged at the first end 11, with the shielding electrode 19 being arranged on the first termination unit 21. The first termination unit 21 can serve to close the winding unit 3 and close any free space between the magnetic core 9 and the winding unit 3. This allows the transformer unit 1 to be closed at the first end 11, preventing the magnetic core 9 from being led out of the winding unit 3, thus contributing to a more robust transformer unit 1.

[0051] Furthermore, the transformer unit 1 has a second termination unit 23 arranged at its second end 13. In another embodiment, a further shielding electrode 19 can be arranged on the second termination unit 23. The second termination unit 23 can serve to terminate the winding unit 3 and close the free space between the magnetic core 9 and the winding unit 3. This allows a transformer unit 1 with a sealed space to be achieved, in which the electrical insulation is improved and the risk of field strength concentrations is reduced. This sealed space helps to ensure the stability of the electric fields within the transformer unit 1, thereby further reducing the risk of partial discharges and flashovers. The second termination unit 23 can also contribute to increasing the mechanical stability and protecting the transformer unit 1 from contamination.

[0052] Figure 2 shows a further schematic partial representation of the transformer unit 1 from Figure 1. The first termination unit 21 has a terminal 25 on one side opposite the shielding electrode 19, connected to the shielding electrode 19, for connecting the high-voltage potential. The terminal 25 allows the shielding electrode 19 to be connected to the high-voltage potential in a particularly simple manner, especially through the space enclosed by the first termination unit 21. This results in a particularly simple connection of the shielding electrode 19 to the high-voltage potential. In particular, this makes the transformer unit 1 particularly easy to use and connect.

[0053] The primary winding 5 is led outwards from the winding unit 3 to the primary terminal 15 at its first end 11. This can be achieved using specially insulated connecting wires or cables that branch off from the ends of the primary winding 5 and pass through the insulating polymer material. Brass bushings, for example, can be used for the primary terminal 15, which can also be referred to as the high-voltage terminal and serves to connect the high voltage to the primary winding 5. Inside the winding unit 3, the primary winding 5, or a strand of the primary winding 5, is connected to the primary terminal 15. Outside the winding unit 3, a cable or strand can be connected to the primary terminal 15 to establish a connection to a high-voltage unit or other electrical components.The primary terminal 15 itself can be equipped with suitable terminal blocks or connectors that allow for a simple and safe connection to the high-voltage unit.

[0054] The winding unit 3 has at least one recess 27 extending through the primary and secondary windings 5, 7. Thus, the winding unit 3 is open at both ends 11, 13, allowing the magnetic core 9 to be positioned within the winding unit 3. The winding unit 3 can therefore have a free space 29 at both ends 11, 13, through which the magnetic core 9 can be passed. The magnetic core 9 has a first U-shaped half-shell 31 and a second U-shaped half-shell 33, which together form an upper core part 35 and an upper U-shaped half-shell of the magnetic core 9, respectively, which can be inserted at the first end 11 of the winding unit 3.

[0055] These U-shaped half-shells 31, 33 can be positioned in the winding unit 3 to close the magnetic circuit and achieve optimal magnetic coupling between the primary and secondary windings 5, 7. The U-shaped half-shells 31, 33 are designed to enable a uniform distribution of the magnetic flux and maximize the overall performance and efficiency of the transformer unit 1.

[0056] In the present embodiment, the magnetic Kem 9 is connected to a low-voltage potential. "Low-voltage potential" also means that the magnetic Kem 9 is grounded, thereby bringing it to earth potential. By grounding the magnetic Kem 9, potential voltages that may arise through induction or malfunction can be safely discharged to earth. This has the advantage of reducing the risk of electrical flashovers.

[0057] The conductive shielding electrode 19 is arranged in the region of the first end 11 and the magnetic core 9 such that the shielding electrode 19 can be brought to a high-voltage potential, thereby generating at least a predominantly homogeneous field between the shielding electrode 19 and the magnetic core 9. At the exit point of the primary terminal 15 or at wires connected to the primary terminal 15, high electric field strengths can occur when the primary terminal 15 is connected to a high voltage. In the case of insufficient electrical insulation and therefore insufficient potential reduction, these high field strengths can increase the risk of partial discharges, flashovers, or breakdowns. The homogeneous electric field is shown in Figure 5.

[0058] The shielding electrode 19 has an arc-shaped cross-section. An arc-shaped cross-section means that the shielding electrode 19 has a rounded or curved shape in its cross-sectional view, preferably without sharp corners or edges. In the present embodiment, the shielding electrode 19 has a circular cross-section. In alternative embodiments, the shielding electrode 19 can have an oval, teardrop, parabolic, or kidney-shaped form. The arc-shaped cross-section reduces the risk of locally increased electric field strengths that can be caused by sharp edges. High field strengths caused by edges or corners can lead to flashovers or corona discharges, which can impair both the efficiency and the safety of the transformer unit 1.The arc-shaped cross-section allows for a more uniform distribution of the electric field and avoids maximizing the field strength at specific points. This contributes to a homogenized field distribution between two potentials, for example, the primary terminal 15 at high voltage and the magnetic core 9 at low voltage.

[0059] Furthermore, the shielding electrode 19 has a torus shape with an elliptical longitudinal section. This means that the shielding electrode 19 is tubular, similar to a bent tube. The torus shape therefore has an elongated, oval-like form in plan view. This has the advantage that the elliptical geometry enables an efficient distribution of the electric field to the magnetic core 9. In addition, the torus shape allows for a robust construction and effective heat dissipation, which can increase the operational reliability and performance of the shielding electrode 19. Figures 3, 4a, and 4b below illustrate how the electric field can lead to field peaks in transformer units 1 known from the prior art without a shielding electrode 19.

[0060] Figure 3 shows a schematic representation of the electric field of a transformer unit 1, as known from the prior art. As already mentioned, the transformer unit 1 known from the prior art does not have a shielding electrode 19. In the representation in Figure 3, the voltage levels are indicated by the different shades of gray, as shown in the scale. Also shown are electric field lines, which represent a transition between different voltage levels. The risk of flashovers is highest where the electric field lines are closest together, as this indicates a high voltage drop and a high field strength. Figure 3 shows that the electric field lines are particularly close together between the primary terminal 15 and the magnetic core 9.

[0061] In general, it can be seen that high electric field strengths occur in the transformer unit 1 without a shielding electrode 19, even where no insulating material is present. This is the case, firstly, outside the winding unit 3, above the first termination unit 21, and secondly, between the first termination unit 21 and the magnetic core 9. As shown in Figure 2 and indicated in Figure 3, there is a free space 29 between the magnetic core 9 and the first termination unit 21. No insulating material is arranged in this free space 29, since the winding unit 3 has an opening at both ends 11, 13 for inserting the magnetic core 9. Therefore, the risk of flashovers is highest in areas without insulating material, especially in the free space 29, due to the air, which has a significantly lower dielectric constant compared to the insulating material.

[0062] Partial discharges typically occur at points with particularly strong concentrated electric fields, so-called field peaks, which exceed the dielectric strength of the insulating material. This is especially true for areas where the electric field passes through materials with a low dielectric constant, such as air. A homogeneous field can ensure a uniform distribution of the electric field strengths and minimize voltage differences between the primary terminal 15 and the magnetic core 9. This can increase the overall insulation strength of the transformer unit 1 and reduce the probability of partial discharges that could lead to flashovers or breakdowns.

[0063] It is also shown that a high field strength occurs between the primary terminal 15 and the magnetic core 9 in a direction perpendicular to the primary terminal 15. As can be seen in Figure 2, the insulating material, which has a high dielectric constant, is arranged in this area, so that the electric field can be reduced in this area, thus lowering the risk of flashovers. Figure 4 below illustrates the electric field of a transformer unit 1 described herein with the shielding electrode 19.

[0064] Figure 4 shows a schematic representation of the electric field of the transformer unit 1 from Figures 1 and 2. In Figure 4, the electric field is again represented by the different shades of gray, with the electric field lines indicated by the transitions between the shades. As already mentioned, the winding unit 3 is open at both ends 11, 13 to allow the insertion of the magnetic core 9. Therefore, the transformer unit 1 has a free space 29 between the magnetic core 9 and the first end 11, in which no insulating material is located. In this area, there is an increased risk of partial discharges, since high electric field strengths or voltage drops can occur between the primary terminal 15, which is at high voltage, and the magnetic core 9, which is at low voltage. These can only be dissipated to a limited extent over the short air path.The risk of partial discharges can be reduced by the shielding electrode 19, since a homogeneous electric field distributes the electric field strengths more evenly and prevents local field peaks. This applies particularly to areas such as the free space 29 and the area above the first termination unit 21, where no insulating material is present.

[0065] The shielding electrode 19 is arranged at least partially along the electric field between the first end 11 and the magnetic core 9. This arrangement of the shielding electrode 19 between the first end 11 and the magnetic core 9 ensures that a homogeneous electric field can be generated in the free space 29 through which the magnetic core 9 is guided, thereby reducing the risk of partial discharges and field spikes. The arrangement along the electric field refers to any arrangement of the shielding electrode 19 that can generate the most homogeneous field possible between the primary terminal 15 and the magnetic core 9.

[0066] The shielding electrode 19 is arranged along a yoke 37 of the magnetic core 9 and, in the present embodiment, has a first width 39 that corresponds to at least 60% of a second width 41 of the yoke 37 of the magnetic core 9. The first width 39 of the shielding electrode 19 and the second width 41 of the yoke 37 are understood to be the extent in the front view of the magnetic core 9, viewed from the front as shown in Figure 4. The first width 39, or the coverage of the shielding electrode 19 relative to the yoke 37, allows for generous coverage of the yoke 37 by the shielding electrode 19, thereby achieving a field that is as homogeneous as possible along the second width 41 of the yoke 37. In the present embodiment, the first width corresponds to at least 160% of a third width 43 of the primary connection 15. The primary connection 15 has at least a first connection 45 and a second connection 47.The extension direction of the primary terminal 15 is defined as the third width 43 from one end of the first terminal 45 to the other end of the second terminal 47. Thus, the third width 43 of the primary terminal 15 encompasses the extension of terminals 45 and 47. The first width 39 of the shielding electrode 19, relative to the primary terminal 15, allows the shielding electrode 19 to cover the primary terminal 15, thereby achieving a field that is as homogeneous as possible along the third width 43 of the primary terminal 15.

[0067] Figure 5 shows a schematic representation of a power electronic converter 49 with the transformer unit 1 from Figures 1 and 2. As already mentioned, the transformer unit 1 can be used in a power electronic converter 49. Such a power electronic converter 49 can, for example, be an SST or a cell of an SST. A cell of an SST can comprise a high-voltage unit 51, a low-voltage unit 53, and a transformer unit 1 as described here. The transformer unit 1 is arranged between the high-voltage unit 51 and the low-voltage unit 53.

[0068] Particularly in transformer units 1 for power electronic converters 49, due to limited installation space, it is necessary to route the primary terminal 15 at one end 11 of the transformer unit 1 in a direction parallel to the winding axis of the primary winding 5. Since power electronic converters 49, such as power electronic converter cells of an SST, in which the transformer unit 1 described here can be used, are flat, the transformer unit 1 itself must also have a flat design or low height. Therefore, the primary winding 5 can be routed to the primary terminal 15 of the transformer unit 1 at the first end 11, and the secondary winding 7 to the secondary terminal 17 of the transformer unit 1 at the second end 13. This results in a particularly flat design for the transformer unit 1.This also has the advantage that a required insulation distance can be maintained between the primary connection and the secondary connection, and therefore also between the high voltage and the low voltage.

[0069] Figure 6 shows a flowchart of a method 100 for manufacturing a transformer unit 1. The method 100 is for manufacturing a transformer unit 1 for a power electronic converter 49 and comprises, in a first step 101, the provision of a winding unit 3, a magnetic core 9, and a shielding electrode 19. In a second step 102, the method 100 comprises inserting the magnetic core 9 into the winding unit 3, and in a third step 103, attaching the shielding electrode 19 to a region of the first end 11 of the winding unit 3 and the magnetic core 9, wherein the shielding electrode 19 can be brought to a high-voltage potential or a low-voltage potential, thereby generating an at least predominantly homogeneous field between the shielding electrode 19 and the magnetic core 9.

[0070] The winding unit 3 has a primary terminal 15 or secondary terminal 17 connected at a first end 11 to the primary winding 5 or the secondary winding 7. The winding unit 3, the magnetic core 9, and the shielding electrode 19 can be the winding unit 3, the magnetic core 9, and the shielding electrode 19 described herein. In particular, the winding unit 3 has a primary and secondary winding 5, 7 embedded in a cured polymer. The magnetic core 9 has, in particular, at least two U-shaped half-shells 31, 33, preferably four U-shaped half-shells, such that the magnetic core 9 has half-shells divided in both the longitudinal and transverse directions. The shielding electrode 19 is provided as a separate component and can be connected to the winding unit 3.This has the advantage that a modular design of the transformer unit 1 is achieved, in which the winding unit 3, the magnetic core 9 and the shielding electrode 19 can be interchangeable.

[0071] In the second step 102, the magnetic core 9 is inserted into the winding unit 3. The winding unit 3 has at least one recess 27 extending through the primary and secondary windings 5, 7. As already mentioned, the winding unit 3 is open at both ends 11, 13, so that the magnetic core 9 can be arranged in the winding unit 3. Accordingly, the winding unit 3 can have the free space 29 at both ends 11, 13 through which the magnetic core 9 can be passed. The magnetic core 9 is inserted into the winding unit 3 by inserting two or four U-shaped half-shells 31, 33 into the winding unit 3 from each side. These U-shaped half-shells 31, 33 can be positioned so that they close the magnetic circuit 9 and achieve magnetic coupling between the primary and secondary windings 5, 7.The U-shells 31, 33 are designed to enable a uniform distribution of the magnetic flux and to improve the overall performance and efficiency of the transformer unit 1.

[0072] In the third step 103, the shielding electrode 19 is attached in a region of the first end 11 of the winding unit 3 and the magnetic core 9, wherein the shielding electrode 19 can be brought to a high-voltage potential or a low-voltage potential, thereby generating at least a predominantly homogeneous field between the shielding electrode 19 and the magnetic core 9. Attachment is understood to mean positioning the shielding electrode 19 relative to the magnetic core 9 or relative to the primary terminal 15 or secondary terminal 17. The shielding electrode 19 can be connected to and positioned relative to the winding unit 3, the primary terminal 15, the secondary terminal 17, or the magnetic core 9. Fastening means can be provided for this purpose, with which the shielding electrode 19 can be attached to the winding unit 3, the primary terminal 15, the secondary terminal 17, or the magnetic core 9.This allows for a particularly precise positioning of the shielding electrode 19, so that a homogeneous field can be generated between the shielding electrode 19 and the magnetic core 9.

[0073] Method 100 involves, in a fourth step 104, connecting the magnetic core 9 to one of the high-voltage and low-voltage potentials, and in a fifth step 105, connecting the shielding electrode 19 to the other of the high-voltage and low-voltage potentials. Thus, the shielding electrode 19 is always brought to, or connected to, a potential different from that of the magnetic core 9. This allows a clear electrical path or a homogeneous field to be created between the two potentials, thereby reducing the risk of electrical arcing between the potentials, particularly in areas where the electric field passes through regions of materials with a low dielectric constant, such as air.

[0074] Method 100 is designed such that when the shielding electrode 19 is arranged at the first end 11, the shielding electrode 19 is connected to a high-voltage potential and the magnetic core 9 to a low-voltage potential. When the shielding electrode 19 is arranged at the second end 13, the shielding electrode 19 is connected to a low-voltage potential and the magnetic core 9 to a high-voltage potential. The transformer unit 1 has primary and secondary terminals 15 and 17 at both the first and second ends 11 and 13, respectively. The primary and secondary terminals 15 and 17 can have terminal sockets that are connected to the primary and secondary windings 5 ​​and 7. Depending on the arrangement of the shielding electrode 19, the shielding electrode 19 and the magnetic core 9 can be brought to a respective potential or connected to a respective voltage level.The shielding electrode 19 can be attached to the first or second end 11, 13 and thus between the magnetic core 9 and the primary or secondary terminal 15, 17. Typically, the primary terminal 15 is connected to a high-voltage potential and the secondary terminal 17 to a low-voltage potential. The magnetic core 9 can be connected to either the high-voltage or the low-voltage potential. Therefore, the magnetic core 9 and the shielding electrode 19 can be connected according to the method 100 described here, depending on the arrangement of the shielding electrode 19. This has the advantage that the shielding electrode 19 does not require a fixed arrangement and the transformer unit 1 can be connected depending on the arrangement of the shielding electrode 19.

[0075] In summary, it can be stated that a transformer unit 1 and a method 100 for manufacturing a transformer unit 1 are provided in which the load on the insulating materials is distributed evenly and the risk of field peaks that could lead to flashovers is minimized. Reference symbol list

[0076] Transformer unit Winding unit Primary winding Secondary winding Magnetic core

[0077] first end

[0078] second ending

[0079] Primary connection Secondary connection Shielding electrode

[0080] first final unit

[0081] second completion unit connection

[0082] recess

[0083] open space

[0084] first U-shaped half-shell

[0085] second U-shaped half-shell

[0086] upper core part

[0087] yoke

[0088] first width

[0089] second width

[0090] third width

[0091] first connection

[0092] second connection of power electronic converter, high-voltage unit, low-voltage unit

[0093] Proceedings

[0094] first step

[0095] second step

[0096] third step 104 fourth step 105 fifth step

Claims

1. Patent claims 1. Transformer unit (1 ) for a power electronic converter (49) with a winding unit (3) with a primary winding (5) and a secondary winding (7), 3. a magnetic core (9) arranged at least partially in the winding unit (3), 4. a primary terminal (15) arranged at a first end (11) of the winding unit (3) and connected to the primary winding (5) for a high-voltage potential, and 5. wherein the magnetic core (9) can be connected to a low voltage potential, 6. wherein a conductive shielding electrode (19) is arranged in the region of the first end (11) and the magnetic core (9) such that the shielding electrode (19) can be brought to a high voltage potential and an at least predominantly homogeneous field can be generated between the shielding electrode (19) and the magnetic core (9).

2. Transformer unit (1 ) for a power electronic converter (49) with a winding unit (3) with a primary winding (5) and a secondary winding (7), 8. a magnetic core (9) arranged at least partially in the winding unit (3), 9. a secondary terminal (17) arranged at a second end (13) of the winding unit (3) and connected to the secondary winding (7) for a low-voltage potential, and 10.whereby the magnetic core (9) can be connected to a high voltage potential, 11. wherein a conductive shielding electrode (19) is arranged in the region of the second end (13) and the magnetic core (9) such that the shielding electrode (19) can be brought to a low voltage potential and an at least predominantly homogeneous field can be generated between the shielding electrode (19) and the magnetic core (9). 12.29 3. Transformer unit (1 ) according to claim 1 or 2, wherein the shielding electrode (19) is arranged at least partially along the electric field between the first or second end (13) and the magnetic core (9).

4. Transformer unit (1) according to claims 1 to 3, wherein the winding unit (3) has an insulating material and the primary winding (5) and the secondary winding (7) are embedded in the insulating material.

5. Transformer unit (1) according to claim 1 or 3, comprising 15. a first termination unit (21) arranged at the first end (11), wherein the shielding electrode (19) is arranged at the first termination unit (21).

6. Transformer unit (1) according to claim 2 or 3, comprising 17. a second termination unit (23) arranged at the second end (13), wherein the shielding electrode (19) is arranged at the second termination unit (23).

7. Transformer unit (1) according to claim 5 or 6, wherein the first or second termination unit (21, 23) has on a side opposite the shielding electrode (19) a connection (25) connected to the shielding electrode (19) for connecting the high voltage potential or the low voltage potential.

8. Transformer unit (1) according to one of the preceding claims, wherein the shielding electrode (19) has an arc-shaped cross-section.

9. Transformer unit (1) according to one of the preceding claims, wherein the shielding electrode (19) extends along a yoke (37) of the magnetic core (9) and has a first width (39) which corresponds to at least 50%, preferably at least 60%, further preferably at least 80%, further preferably 100%, of a second width (41) of the yoke (37) of the magnetic core (9). 21.30 10. Transformer unit (1) according to one of the preceding claims, wherein the shielding electrode (19) extends in a direction perpendicular to the primary terminal (15) and has a first width (39) which corresponds to at least 100%, preferably at least 120%, further preferably at least 150%, of a third width (43) of the primary terminal (15).

11. Method (100) for manufacturing a transformer unit (1) for a power electronic converter (49), comprising the following steps:

23. Providing (101) a winding unit (3), a magnetic core (9) and a shielding electrode (19), wherein the winding unit (3) has a primary terminal (15) or secondary terminal (17) connected at a first end (11) and to the primary winding (5) or the secondary winding (7), 24. Inserting (102) the magnetic core (9) into the winding unit (3), 25. Attaching (103) the shielding electrode (19) in a region of the first end (11) of the winding unit (3) and the magnetic core (9), wherein the shielding electrode (19) can be brought to a high-voltage potential or a low-voltage potential and thereby generating an at least predominantly homogeneous field between the shielding electrode (19) and the magnetic core (9).

12. Method (100) according to claim 11, comprising the following step:

27. Connecting (104) the magnetic core (9) to a high-voltage potential and a low-voltage potential, 28. Connecting (105) the shielding electrode (19) to the other high voltage potential and low voltage potential.

13. Use of a transformer unit (1) for a power electronic converter (49) according to any one of claims 1 to 10, 30. wherein when the shielding electrode (19) is arranged at the first end (11 ), the shielding electrode (19) is connected to a high voltage potential and the magnetic core (9) to a low voltage potential, and wherein when the shielding electrode (19) is arranged at the second end (13), the shielding electrode (19) is connected to a low voltage potential and the magnetic core (9) to a high voltage potential.

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