Electrical components, especially transformers or inductors

Abstract

An electrical component is proposed, comprising a ferromagnetic core (10) having first and second legs (11, 12), and a primary winding (20) having a first primary winding section (21) arranged around the first leg (11) of the ferromagnetic core and a second primary winding section (22) arranged around the second leg (12) of the ferromagnetic core, each of the first primary winding section (21) and the second primary winding section (22) including a plurality of parallel-connectable conductors (1, 2, 3, 4, 5, 6) arranged in cross section around the ferromagnetic core, the plurality of conductors (1, 2, 3, 4, 5, 6) being radially oriented relative to one another in a radial row position, and the conductors of the first primary winding section (21) The number of conductors (1, 2, 3, 4, 5, 6) is equal to the number of conductors (1, 2, 3, 4, 5, 6) of the second primary winding section (22), and each of the conductors (1, 2, 3, 4, 5, 6) of the first primary winding section (21) is connected in series with each of the conductors (1, 2, 3, 4, 5, 6) of the second primary winding section (22), whereby the radially outer row of conductors (1, 2, 3, 4, 5, 6) of the first primary winding section (21) is connected with the radially inner row of conductors (1, 2, 3, 4, 5, 6) of the second primary winding section (22), thereby reducing the total magnetic flux between the parallel-connectable conductors (1, 2, 3, 4, 5, 6) of the first and second primary winding sections (21, 22).

Description

[Technical field]

[0001] Technical Field FIELD OF THE DISCLOSURE Embodiments of the present disclosure relate to electrical components having winding arrangements for high voltage applications. In particular, embodiments of the present disclosure relate to transformers, especially oil-filled or dry-cast medium frequency transformers (MFTs) and inductors. [Background technology]

[0002] background Medium frequency transformers (MFTs) are key components in various power electronic systems. Examples in rail vehicles are auxiliary converters, and solid-state transformers (SSTs) replacing large low frequency transformers. Further applications of SSTs are being considered, for example, for grid integration of renewable energy sources, electric vehicle (EV) charging infrastructure, data centers, or power grids onboard ships. SSTs are expected to play an increasingly important role in the future.

[0003] With operating frequencies in the range of tens of kHz, the MFT windings may be made of Litz wire or foil to keep surface wave and proximity effect losses within acceptable limits.

[0004] As soon as two or more Litz wires or foils are connected in parallel, there is a risk that circulating currents are introduced between the wires by the magnetic flux. These currents can strongly increase, for example by a factor of two, the winding losses beyond those caused just by the skin effect and the proximity effect at the level of the individual wires or foils.

[0005] The same problem would occur with inductors having multiple parallel connected conductors, for example Litz wire or foil.

[0006] Therefore, a solution is needed to reduce the circulating currents in the parallel circuits of conductors in electrical components. To avoid these circulating currents, careful winding design is required. Summary of the Invention [Means for solving the problem]

[0007] overview In view of the above, an electrical component, in particular a transformer or inductor, is provided. Further aspects, advantages, and features are apparent from the dependent claims, the description, and the accompanying drawings.

[0008] According to an aspect of the present disclosure, an electric component is proposed, the electric component comprising: a ferromagnetic core having a first leg and a second leg; a primary winding having a first primary winding section disposed around the first leg of the ferromagnetic core and a second primary winding section disposed around the second leg of the ferromagnetic core, each of the first primary winding section and the second primary winding section including a plurality of conductors, the plurality of conductors being parallel connectable and disposed around the ferromagnetic core in a cross section, the plurality of conductors being radially offset relative to each other in a radial row position, the number of conductors of the first primary winding section being equal to the number of conductors of the second primary winding section, each of the conductors of the first primary winding section being connected in series with each of the conductors of the second primary winding section, whereby the conductors of the radially outer row of the first primary winding section are connected in series with the conductors of the radially inner row of the second primary winding section to reduce a sum of magnetic flux between the parallel connectable conductors of the first primary winding section and the parallel connectable conductors of the second primary winding section.

[0009] The design of the electrical component of the present disclosure is therefore an improvement compared to the conventional construction of electrical components of this type. In particular, a reduction in the sum of the magnetic flux or the total magnetic flux of the primary winding between the parallel-connectable conductors of the first and second primary winding sections is for a situation in which the radially outer row of conductors of the first primary winding section is connected in series with the radially outer row of conductors of the second primary winding section. In other words, a swap of the radial conductor positions on the first leg with respect to the radial conductor positions on the second leg is proposed.

[0010] The term "parallel connectable" describing conductors should be understood as meaning that the conductors are not electrically connected in series. Furthermore, the conductors can be separated from each other, for example by an insulator. Typical conductors are, for example, Litz wires arranged in a cable formed by a group of Litz wires, or foils arranged as a stack of layers. Note that parallel connectable does not necessarily mean that the conductors form an electrical parallel circuit inside the device. The actual electrical connection of parallel conductors may be part of an electrical component or within the preferred range of use of the electrical component. Parallel connectable should be understood as at least connectable in an electrical parallel circuit.

[0011] A primary winding arrangement having a first primary winding section disposed around a first leg of a ferromagnetic core and a second primary winding section disposed around a second leg of the ferromagnetic core is also known as a core type, e.g. in a core-type transformer.

[0012] A plurality of parallel-connectable conductors are arranged around the ferromagnetic core in cross section, and the conductors are radially offset relative to one another in a radial row position. In other words, the conductors surround the first or second legs, respectively, at different radii. Due to the different radii, magnetic flux exists in the axial direction of the first and second primary winding sections, i.e., between the radially inner and outer conductors. This magnetic flux, if not compensated, will induce a circulating current between the radially inner and outer conductors.

[0013] According to one embodiment, the first and second primary winding sections may include multiple turns of a conductor around the first or second leg of the ferromagnetic core. The cross-section of the conductor is equal for each turn. The turns may be arranged radially or radially and axially as a spiral or helix.

[0014] According to one embodiment, the conductors of the first and second primary winding sections are foils. The foils can be arranged in a foil stack, and the stack can be arranged around a ferromagnetic core. The parallel-connectable foils of the first primary winding section are connected with the parallel-connectable foils of the second primary winding section, such that the radially outer row of foils of the first primary winding section are connected in series with the radially inner row of conductors of the second primary winding section. This interchange between the two series-connected primary winding sections creates opposing magnetic fluxes that cancel each other out, or at least significantly reduce the total magnetic flux.

[0015] According to an aspect, each of the first and second primary winding sections includes at least three conductors. In some embodiments, each of the second primary winding sections includes four or six conductors.

[0016] Preferably, each of the conductors of the first primary winding section is a continuous conductor. Thus, each of the conductors of the second primary winding section is a continuous conductor. Each of the conductors of the first primary winding section is serially connectable with each of the conductors of the second primary winding section, for example by cable lugs. At the external input or output, all conductors may fit within one cable lug per winding section, resulting in a parallel circuit of conductors that can be connected in parallel.

[0017] According to one aspect, the electrical component further comprises a first external electrical connector connected in series with the conductors of the first primary winding portion and a second external electrical connector connected in series with the conductors of the second primary winding portion, the first and second primary winding portions being located between the first and second external electrical connectors. The first and second external electrical connectors may be cable lugs.

[0018] According to an embodiment, the electrical component is a transformer, further comprising a secondary winding having a first secondary winding portion disposed about a first leg of the ferromagnetic core and a second secondary winding portion disposed about a second leg of the ferromagnetic core.

[0019] According to an embodiment, the transformer is an MTF. Typical frequencies and currents of the operating conditions for which the transformer can be applied are, for example, 0.5 kHz to 50 kHz, in particular 10 kHz to 20 kHz, and currents in the range of 20 A to 2000 A, in particular 100 A to 2000 A.

[0020] The secondary winding may be an inner winding, and the secondary winding may be a low-voltage winding. According to yet another development of the invention, the first and second secondary winding sections may include a plurality of parallel-connectable conductors, each of the conductors of the first secondary winding section may be connected in series with each of the conductors of the second secondary winding section, similar to the primary winding described herein. Alternatively, the first and second secondary winding sections may be connected in any possible way, provided that the magnetic flux does not affect the operability of the electronic device. Typically, the effect is small in the case of LV windings.

[0021] According to another embodiment, the electrical component is an inductor. According to an embodiment, the first and second primary winding sections are substantially geometrically symmetric, in particular the number of conductors of the first and second winding sections are equal, the number of radial rows of the cross section are equal, the number of axial rows of the cross section are equal, and / or the number of turns around the legs of the ferromagnetic core are equal. The more the first and second primary winding sections are equal to each other, the more the magnetic flux between the parallel-connectable conductors of the first and second primary winding sections is cancelled by the proposed series connection of the conductors.

[0022] The axial and radial rows are defined by an axial direction and a radial direction, the radial direction being from the legs of the ferromagnetic core towards the primary winding, and the axial direction being perpendicular to the radial direction and along the legs of the ferromagnetic core.

[0023] The primary winding may include a plurality of turns around the legs of the ferromagnetic core, the cross-sections of the plurality of parallel connectable conductors being substantially equal in each turn. The turns can be arranged in the radial or axial direction or in both directions. In one example, the primary winding includes a plurality of parallel connectable foils having a cross-section, the conductors being radially offset relative to each other in a radial row position. The primary winding may include, for example, 10 radial turns. In each turn, the cross-sections of the foils are substantially equal, meaning that the radial row position of each foil is constant relative to each other. In another example, the primary winding includes a plurality of parallel connectable Litz wires. The primary winding includes, for example, 10 axially arranged turns such that a cable formed of a group of Litz wires forms a spiral. In each turn, the cross-sections of the cable are substantially equal, meaning that the radial row position and the axial row position of each Litz wire in the cable are constant relative to each other.

[0024] According to an embodiment, each of the first primary winding section and the second primary winding section includes a cable formed of a plurality of Litz wires, and the plurality of parallel connectable conductors is a plurality of parallel connectable Litz wires. The conductors are identified as Litz wires. Litz wires typically consist of a plurality of strands that are electrically insulated from one another. The strands are typically twisted. Each strand may have a diameter of, for example, 0.2 mm, and the Litz wire may consist of 100 Litz strands. The Litz wire may have a substantially rectangular cross section, for example, 6 mm by 12 mm.

[0025] Preferably, the multiple parallel connectable conductors are arranged around the ferromagnetic core in cross section, with the conductors being radially offset from one another in a radial row position, and the radial position, and typically also the axial position, does not change along the length of the first or second primary winding section. In the example of Litz wires grouped in a cable, the Litz wires are not twisted. The cable may include multiple Litz wires, for example, four or six Litz wires. Thus, the cross section of the multiple Litz wires remains constant, for example, such that the Litz wires located radially outside the primary winding are maintained radially outside along the entire length of the first or second primary winding section.

[0026] According to an embodiment, each of the first and second primary winding sections has a substantially spiral symmetry. A cross section of the plurality of parallel-connectable conductors winds around a central axis. Each of the first and second primary winding sections may have a substantially cylindrical shape.

[0027] According to other embodiments, each of the first and second primary winding sections may be substantially spirally symmetric. The first and second primary winding sections may have a spiral or helical symmetry. The cross sections of the multiple parallel-connectable conductors wind around a central axis. The cross sections may also wind along the central axis, for example if the conductors are Litz wires.

[0028] According to one embodiment, each of the multiple parallel-connectable conductors has a defined radial, and possibly axial, position in cross-section of the conductor over the entire length of the first and / or second primary winding section, in other words, there is no radial or axial permutation of the conductors within the first and / or second primary winding section.

[0029] The first and second primary winding sections may be formed by Litz wire arranged as a closed, packed spiral around the first and second legs, respectively, of the ferromagnetic core.

[0030] According to this embodiment, or other embodiments in which axial rows of conductors are also present in the cross-sectional view, the H field has radial components near the axial top and bottom ends of the first and second primary winding parts, so that further axial magnetic fluxes can be generated in the parallel-connectable conductors. The radial magnetic flux is typically smaller than the axial magnetic flux. However, the radial H components are asymmetric, for example pointing radially outward at the axial top of the first and second primary winding parts and radially inward at the bottom, or vice versa. In contrast, the axial H components are symmetric and point in the same direction at the top and bottom, for example pointing vertically upward. The radial components of the resulting magnetic flux therefore cancel each other out without any shuffling.

[0031] According to an embodiment, the cable includes four Litz wires, the Litz wires of the first and second primary winding sections being arranged in the cable around the ferromagnetic core in a cross section including two radial rows and two axial rows, the axial direction defining an axial top row and an axial bottom row, the Litz wires of the top row of the first primary winding section being connected in series with the Litz wires of the top row of the second primary winding section, and the Litz wires of the bottom row of the first primary winding section being connected in series with the Litz wires of the bottom row of the second primary winding section.

[0032] Multi-Litz wire cables having four Litz wires are typically used in applications where a current of at least 100 A, typically greater than 300 A, flows through the first and second primary winding sections under operating conditions.

[0033] According to another aspect, the cross section of the multiple conductors may include three or more axial rows. This reduces the magnitude of the axial magnetic flux axially from the ends of the primary winding toward the center, thus introducing further axial magnetic flux if the conductors are not axially permuted. Thus, according to an embodiment, the litz wire or other type of conductor of the first and second primary winding sections is arranged around the ferromagnetic core in a cross section including K≧3 axial rows of litz wire. Each row is arranged in an axial row position, with the axial end row position being row position number 1 and the opposite axial end row position being row position number K, and each litz wire in the k row position of the first primary winding section with 1≦k≦K is connected in series with a litz wire in the K+1-k row position of the second primary winding section. This reduces the total magnetic flux between the parallel connectable litz wires of the first and second primary winding sections.

[0034] So that the above recited features of the present disclosure can be understood in detail, a more particular description of the present disclosure briefly summarized above can be had by reference to embodiments, the accompanying drawings of which relate to embodiments of the present disclosure and which are described below. [Brief description of the drawings]

[0035] [Figure 1] FIG. 2 is a schematic diagram of an electrical component, specifically a transformer, according to embodiments described herein. [Diagram 2] 4 is a detailed schematic cross-sectional view of a cross section of a primary winding portion according to embodiments described herein. [Diagram 3] FIG. 13 is a detailed schematic cross-sectional view of a cross section of a primary winding portion according to another embodiment. [Figure 4A] 1 illustrates an embodiment of primary and secondary windings around legs of a ferromagnetic core in accordance with the present disclosure. [Figure 4B] 1 illustrates an embodiment of primary and secondary windings around legs of a ferromagnetic core in accordance with the present disclosure. [Figure 5A] 4 is a schematic diagram illustrating the magnetic flux in a primary winding section and the series connection of conductors of the first and second primary winding sections according to an embodiment. FIG. [Figure 5B] 2 is a schematic diagram illustrating magnetic flux in a primary winding section and a series connection of conductors of first and second primary winding sections according to an embodiment. FIG. [Figure 6A] FIG. 11 is another schematic diagram illustrating the magnetic flux in the primary winding section and the series connection of conductors of the first and second primary winding sections according to certain other embodiments. [Figure 6B] FIG. 11 is another schematic diagram illustrating the magnetic flux in the primary winding section and the series connection of conductors of the first and second primary winding sections according to another embodiment. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0036] Detailed Description of the Embodiments Reference will now be made in detail to various embodiments, one or more examples of which are illustrated in the figures. Each example is provided by way of illustration and not by way of limitation. For example, features illustrated or described as part of one embodiment can be used on or in conjunction with other embodiments to yield still other embodiments. The present disclosure is intended to include such modifications and variations.

[0037] In the following description of the drawings, the same reference numbers represent the same or similar components. Generally, only the differences with respect to the individual embodiments are described. Unless otherwise specified, the description of a part or aspect of one embodiment may also apply to a corresponding part or aspect of other embodiments.

[0038] With exemplarily reference to FIG. 1, an electrical component is shown. The electrical component of FIG. 1 is a transformer according to an embodiment, which can be combined with other embodiments described herein. In particular, according to other embodiments, the electrical component may be an inductor. The electrical component comprises a ferromagnetic core 10 having first and second legs 11, 12, and a primary winding 20 having a first primary winding section 21 arranged around the first leg 11 of the ferromagnetic core and a second primary winding section 22 arranged around the second leg 12 of the ferromagnetic core, each of the first primary winding section 21 and the second primary winding section 22 including a plurality of parallel-connectable conductors 1, 2, 3, 4, 5, 6 arranged around the ferromagnetic core in cross section, the conductors being radially offset with respect to each other in a radial row position, and the number of conductors 1, 2, 3, 4, 5, 6 of the first primary winding section 21 being equal to or larger than the number of conductors of the second primary winding section 20 being equal to or larger than the number of conductors of the first primary winding section 21 in the second primary winding section 20. The number of conductors 1, 2, 3, 4, 5, 6 of the first primary winding section 21 is equal to the number of conductors 1, 2, 3, 4, 5, 6 of the primary winding section 22, and each of the conductors 1, 2, 3, 4, 5, 6 of the first primary winding section 21 is connected in series with each of the conductors 1, 2, 3, 4, 5, 6 of the second primary winding section 22, whereby the conductors 1, 2, 3, 4, 5, 6 of the radially outer row of the first primary winding section 21 are connected in series with the conductors 1, 2, 3, 4, 5, 6 of the radially inner row of the second primary winding section 22, reducing the total magnetic flux between the parallel-connectable conductors 1, 2, 3, 4, 5, 6 of the first primary winding section 21 and the parallel-connectable conductors 1, 2, 3, 4, 5, 6 of the second primary winding section 22.

[0039] 1 is a transformer and further includes a secondary winding 30 having a first secondary winding portion 31 disposed about a first leg 11 of the ferromagnetic core and a second secondary winding portion 32 disposed about a second leg 12 of the ferromagnetic core. The primary and secondary windings are separated by insulation.

[0040] Due to the insulation, the primary winding section 21 / 22 is maintained at a greater distance from the secondary winding section 31 / 32 and the ferromagnetic core 10 than the distance between the secondary winding section 31 / 32 and the ferromagnetic core 10. The insulation distance is shown diagrammatically in FIG. 1. This reduces the height of the primary winding section 21 / 22 compared to the height of the secondary winding section 31 / 32. To account for the reduced height, the radial thickness of the primary winding 20 must be greater than the radial thickness of the secondary winding 30 to provide a sufficient conductor cross-section. Each primary winding section 21, 22 therefore has two or more rows of conductors radially offset with respect to each other.

[0041] The ferromagnetic core 10 is suitable for a core-type transformer. The shape of the ferromagnetic core 10 may include, for example, a CC, UU, UI or LL shape, with two components forming an "O" shaped ring. The ferromagnetic core has at least two legs 11, 12, which are not necessarily parallel to each other, although this is preferred. Each leg 11, 12 defines a separate space for the first primary winding section 21 and the second primary winding section 22, so that the first and second primary winding sections do not spatially overlap.

[0042] According to yet another embodiment, the electrical component may be an inductor. Typically, an inductor only has a primary winding 20. A secondary winding 30 is not required.

[0043] The electrical component may comprise a first external electrical connector 41 connected in series with the conductors 1, 2, 3, 4, 5, 6 of the first primary winding section 21 and a second external electrical connector 41 connected in series with the conductors 1, 2, 3, 4, 5, 6 of the second primary winding section 22, the first and second primary winding sections 21, 22 being located between the first and second external electrical connectors 41, 42 as shown in Figure 1. All the conductors 1, 2, 3, 4, 5, 6 may be connected in series with the external electrical connectors 41, 42 to create a parallel circuit of the conductors 1, 2, 3, 4, 5, 6.

[0044] In Fig. 1, the first and second primary winding sections 21, 22 are arranged as outer windings, and the first and second secondary winding sections 31, 32 are arranged as inner windings. Preferably, the first and second primary winding sections 21, 22 are both inner or outer windings. It is preferred that the first and second primary winding sections 21, 22 are symmetrical because the magnetic fluxes cancel each other most when the magnetic flux references are equal and the magnetic fluxes point in opposite directions.

[0045] According to an embodiment, the primary winding 20 is an outer winding and an HV winding, and the secondary winding 30 is an inner winding and an LV winding.

[0046] Figures 2 and 3 show two different embodiments of the arranged parallel-connectable conductors in cross section. They show a cross section of the first or second primary winding section 21, 22. Typically, the first and second primary winding sections 21, 22 have the same structure. Figures 2 and 3 show, for example, a more detailed structure of the left part of the first primary winding section 21 shown in Figure 1.

[0047] In Fig. 2, the conductors 1, 2, 3, 4 are foils. The foils 1, 2, 3, 4 are arranged in cross-section. In the embodiment of Fig. 2, the primary winding 21 includes two turns, so the cross-section is shown twice. The radial positions of the foils 1, 2, 3, 4 in the two cross-sections are identical.

[0048] According to another embodiment shown in FIG. 3, the conductors 1, 2, 3, 4 are Litz wires. The Litz wires 1, 2, 3, 4 are arranged in a cable formed of groups of Litz wires. The cable has a cross section as shown in FIG. 3. The first primary winding section 21 comprises a number of turns of the cable arranged as a spiral. The cross section is essentially the same for each turn, in particular the radial and axial position of each Litz wire is the same for each cross section. There is no interchange of the conductors 1, 2, 3, 4 within the primary winding sections 21, 22. The series connection of the conductors 1, 2, 3, 4 of the first and second primary winding sections 21, 22 is further explained in FIGS. 5A-6B.

[0049] In the embodiment of Fig. 3, the first primary winding section 21 comprises multiple turns of Litz wire arranged as a spiral. According to other embodiments, the first primary winding section 21 may comprise one or more further radial turns of cable forming inner and outer spirals or multiple spirals radially offset from one another. The second primary winding section 22 may thus have the same structure.

[0050] 4A and 4B show different embodiments of the first primary and secondary winding sections 21, 31 arranged around the legs 11 of the ferromagnetic core 10 according to the embodiment. The electrical component in this embodiment is a transformer, further comprising a secondary winding 30 (not shown) having a first secondary winding section 31 arranged around the first leg 11 of the ferromagnetic core and a second secondary winding section 32 arranged around the second leg 12 of the ferromagnetic core. In FIG. 4A, the primary winding 20 is an outer winding and the secondary winding 30 is an inner winding. Thus, the first secondary winding section 31 is arranged radially closer to the first leg 11 of the ferromagnetic core 10 than the first primary winding section 21 arranged around the first secondary winding section 31.

[0051] 4A and 4B, the first primary winding portion 21 is shown to include two turns for ease of illustration. However, the first primary winding portion 21, 22 may include multiple turns, for example, 10 to 20 turns.

[0052] 4B, the primary winding 20 is the inner winding and the secondary winding 30 is the outer winding. Thus, the first primary winding section 21 is positioned radially closer to the first leg 11 of the ferromagnetic core 10 than the first secondary winding section 31. However, regardless of which winding 20, 30 is the inner winding, typically the first and second primary winding sections 21, 22 are equal, i.e., both are either the inner winding section or the outer winding section.

[0053] Between the primary and secondary windings 20, 30 there exists a stray magnetic field oriented in the axial direction of the windings 20, 30, perpendicular to the cross-sectional view shown in FIG. 4B. According to Ampere's law, the magnetic field increases from zero outside the windings 20, 30 to a maximum value between the windings 20, 30. In the inner windings, the magnetic field increases radially from zero to a maximum value. In the outer windings, the magnetic field decreases to zero. Moving radially outwards in the inner windings, there is a normalized field intensity of 1 after the first foil 1, a field intensity of 2 after the second foil 2, etc. According to the invention, the foils are swapped between the first and second primary winding parts 21, 22 in such a way that the magnetic flux passing through the loop formed by the parallel-connectable foils 1, 2, 3 cancels out or is at least significantly reduced.

[0054] In the embodiment of Figures 4A / 4B, foil 1 is the radially innermost foil, foil 3 is the radially outermost foil and foil 2 is located between them. In general, the conductors 1, 2, 3, 4, 5, 6 of the radially outer row of the first primary winding section 21 are connected in series with the conductors 1, 2, 3, 4, 5, 6 of the radially inner row of the second primary winding section 22. Therefore, at least two foils need to be swapped.

[0055] According to an embodiment, the first and second primary winding sections 21, 22 are arranged around the ferromagnetic core in a cross section including M rows of conductors 1, 2, 3, 4, 5, 6, each row being arranged in a radial row position, with the radially innermost row position being row position number 1 and the radially outermost row position being row position number M, and each conductor 1, 2, 3, 4, 5, 6 in the m row position of the first primary winding section with 1≦m≦M is connected in series with a conductor 1, 2, 3, 4, 5, 6 in the M+1-m row position of the second primary winding section. According to the numbering in Figures 4A / 4B, foils 1 and 3, 2 and 2, and 3 and 1 of the first and second primary winding sections 21, 22 are connected in series, respectively.

[0056] According to an embodiment, each of the first primary winding section 21 and the second primary winding section 22 includes a cable formed of a group of litz wires 1, 2, 3, 4, 5, 6.

[0057] FIG. 5A shows the magnetic flux in the first and second primary winding sections 21, 22. The axial direction (z) is shown from bottom to top in FIG. 5A, and the radial direction (4) is shown from left to right. The magnetic flux has an axial component (Hz) and a radial component (Hr). The axial magnetic flux is caused by the difference in radial distance from the ferromagnetic core 10 to the first and second secondary winding sections 31, 32. In FIG. 5A, the magnetic flux is shown upside down so that it points in the same direction. The conductors 1, 2, 3, 4 are arranged in a helix to form the first and second primary winding sections 21, 22.

[0058] FIG. 5B illustrates the axial and radial components of magnetic flux between the parallel connectable conductors of the first and second primary winding sections 21, 22. As shown, the magnetic flux points in different directions, shown as positive and negative. The magnetic flux is antisymmetric. FIG. 5B also illustrates the connection of conductors 1, 2, 3, 4 between the first and second primary winding sections 21, 22.

[0059] In this embodiment, the litz wires 1, 2, 3, 4 of the first and second primary winding sections 21, 22 are connected such that wires 1 and 4 exchange positions and wires 2 and 3 exchange positions as shown in Fig. 5A / 5B, with litz wires 1 and 2 in the inner row position and litz wires 3 and 4 in the outer row position. The exchange of positions between the radially inner and outer litz wires 1, 2, 3, 4 does not necessarily include an exchange between the top and bottom litz wires 1, 2, 3, 4. In other words, wires 1 and 4 are at the bottom of both primary winding sections 21, 22, while wires 2 and 3 are at the top of both primary winding sections. Such a series connection completely cancels the axial and radial magnetic fluxes between all loops formed by the four parallel litz wires 1, 2, 3, 4. Therefore, the circulating current due to such magnetic flux is eliminated.

[0060] Figures 6A and 6B show another embodiment in which the primary winding includes six conductors 1, 2, 3, 4, 5, 6. Compared to the embodiment of Figure 5A, the embodiment of Figure 6A includes two more conductors 5, 6. The conductors 1, 2, 3, 4, 5, 6 are arranged in a cross section with two radial rows and three axial rows. In the cross section of the conductors, the conductors 1, 2 and 3 are arranged in a radially inner position, and the conductors 4, 5 and 6 are arranged in a radially outer position. The cancellation of the axial magnetic flux works similarly to Figures 5A and 5B. In the absence of axial transposition, the cancellation of the axial magnetic flux does not work completely any more, because the magnitude of the radial magnetic flux decreases axially from the end to the center of the primary winding. The magnetic flux is illustrated in Figure 6A. The right side of Figure 6A is shown upside down, similar to Figure 5A. For example, at the bottom of the first primary winding section 21, the radial flux between Litz wire {1, 6} and Litz wire {2, 5} is greater than the radial flux between Litz wire {2, 5} and Litz wire {3, 4}. This is shown by the change in the angle of the H-field vector.

[0061] According to this embodiment, the cross section of the conductor includes K≧3 axial rows of litz wires 1, 2, 3, 4, 5, 6, as shown in Fig. 6A. Each row is arranged in an axial row position, with an axial end row position having row position number 1 and an opposite axial end row position having row position number K, and each litz wire 1, 2, 3, 4, 5, 6 in the k row position of the first primary winding section 21, where 1≦k≦K, is connected in series with a litz wire 1, 2, 3, 4, 5, 6 in the K+1-k row position of the second primary winding section 22 to reduce the total magnetic flux between the parallel-connectable litz wires 1, 2, 3, 4, 5, 6 of the first and second primary winding sections 21, 22.

[0062] FIG. 6B shows a series connection of conductors 1, 2, 3, 4, 5, 6 of the first and second primary winding sections 21, 22.

[0063] Reference number [Explanation of symbols]

[0064] 1 Conductor 2 Conductors 3 Conductors 4 Conductors 5 Conductors 6 Conductors 10 Ferromagnetic Core 11 First Leg 12 Second Leg 20 Primary Winding 21 First primary winding section 22 Second primary winding section 30 Secondary Winding 31 First secondary winding section 32 Secondary Winding Section 41 first external electrical connector 42 second external electrical connector

Claims

1. An electrical component, A ferromagnetic core (10) having a first leg and a second leg (11, 12); a primary winding (20) having a first primary winding portion (21) disposed around the first leg (11) of the ferromagnetic core and a second primary winding portion (22) disposed around the second leg (12) of the ferromagnetic core; a secondary winding (30) having a first secondary winding portion (31) arranged around the first leg (11) of the ferromagnetic core and a second secondary winding portion (32) arranged around the second leg (12) of the ferromagnetic core, the electrical component being a transformer; each of the first primary winding section (21) and the second primary winding section (22) includes a plurality of conductors, the plurality of conductors being parallel connectable and arranged in cross section around the ferromagnetic core, the plurality of conductors being radially offset relative to one another in radial row positions, the number of conductors in the first primary winding section (21) being equal to the number of conductors in the second primary winding section (22), each of the conductors in the first primary winding section (21) being connected in series with each of the conductors in the second primary winding section (22), whereby a radially outer row of conductors in the first primary winding section (21) is connected in series with a radially inner row of conductors in the second primary winding section (22) to reduce a total magnetic flux between the parallel connectable conductors of the first primary winding section (21) and the parallel connectable conductors of the second primary winding section (22); an axial length of an outer winding of the primary winding (20) and the secondary winding (30) is smaller than an axial length of an inner winding of the primary winding (20) and the secondary winding (30); a radial thickness of the outer winding is greater than a radial thickness of the inner winding; each of the first primary winding portion (21) and the second primary winding portion (22) includes a cable formed of a group of Litz wires, and the plurality of parallel-connectable conductors is a plurality of parallel-connectable Litz wires; The cable includes four Litz wires, the Litz wires of the first and second primary winding sections (21, 22) being arranged around the ferromagnetic core (10) in a cross section including two radial rows and two axial rows, the axial direction defining an axial top row and an axial bottom row, whereby the Litz wires of the top row of the first primary winding section (21) are connected in series with the Litz wires of the top row of the second primary winding section (22), and the Litz wires of the bottom row of the first primary winding section (21) are connected in series with the Litz wires of the bottom row of the second primary winding section (22).

2. 2. The electrical component of claim 1, wherein the first and second primary winding sections (21, 22) are arranged around the ferromagnetic core in a cross section including M rows of conductors, each row being arranged at a radial row position, with the radially innermost row position being row position number 1 and the radially outermost row position being row position number M, and each conductor in the mth row position of the first primary winding section (21), where 1≦m≦M, is connected in series with a conductor in the (M+1−m)th row position of the second primary winding section (22).

3. 3. The electrical component of claim 1, wherein the secondary winding (30) is a low voltage winding and the primary winding (20) is a high voltage winding.

4. The electrical component of any one of claims 1 to 3, wherein each of the first primary winding portion (21) and the second primary winding portion (22) includes at least three conductors.

5. The electrical component according to any one of the preceding claims, wherein in an operating state of the electrical component, a current of at least 20 A flows through the primary winding (20).

6. The electrical component according to any one of claims 1 to 5, comprising a first external electrical connector (41) connected in series with the conductors of the first primary winding portion (21) and a second external electrical connector (42) connected in series with the conductors of the second primary winding portion (22), the first and second primary winding portions (21, 22) being located between the first and second external electrical connectors (41, 42).

7. An electrical component, A ferromagnetic core (10) having a first leg and a second leg (11, 12); a primary winding (20) having a first primary winding portion (21) disposed around the first leg (11) of the ferromagnetic core and a second primary winding portion (22) disposed around the second leg (12) of the ferromagnetic core; a secondary winding (30) having a first secondary winding portion (31) arranged around the first leg (11) of the ferromagnetic core and a second secondary winding portion (32) arranged around the second leg (12) of the ferromagnetic core, the electrical component being a transformer; each of the first primary winding section (21) and the second primary winding section (22) includes a plurality of conductors, the plurality of conductors being parallel connectable and arranged in cross section around the ferromagnetic core, the plurality of conductors being radially offset relative to one another in radial row positions, the number of conductors in the first primary winding section (21) being equal to the number of conductors in the second primary winding section (22), each of the conductors in the first primary winding section (21) being connected in series with each of the conductors in the second primary winding section (22), whereby a radially outer row of conductors in the first primary winding section (21) is connected in series with a radially inner row of conductors in the second primary winding section (22) to reduce a total magnetic flux between the parallel connectable conductors of the first primary winding section (21) and the parallel connectable conductors of the second primary winding section (22); an axial length of an outer winding of the primary winding (20) and the secondary winding (30) is smaller than an axial length of an inner winding of the primary winding (20) and the secondary winding (30); a radial thickness of the outer winding is greater than a radial thickness of the inner winding; each of the first primary winding portion (21) and the second primary winding portion (22) includes a cable formed of a group of Litz wires, and the plurality of parallel-connectable conductors is a plurality of parallel-connectable Litz wires; the litz wires of the first and second primary winding sections (21, 22) are arranged around the ferromagnetic core (10) in a cross section including K≧3 axial rows of litz wires, each row being arranged in an axial row position, an axial end row position being row position number 1 and an opposite axial end row position being row position number K, and each litz wire in the kth row position of the first primary winding section (21), where 1≦k≦K, is connected in series with a (K+1−k)th litz wire of the second primary winding section (22) to reduce a total magnetic flux between the parallel-connectable litz wires of the first primary winding section (21) and the parallel-connectable litz wires of the second primary winding section (22).

8. 8. The electrical component of claim 7, wherein the cable includes six Litz wires, the Litz wires of the first and second primary winding portions (21, 22) being arranged around the ferromagnetic core (10) in a cross section including two radial rows and three axial rows.

9. The electrical component according to any one of claims 1 to 8, wherein the first secondary winding portion (31) and the second secondary winding portion (32) are connectable in parallel.

10. The electrical component according to any one of claims 1 to 8, wherein the first secondary winding portion (31) and the second secondary winding portion (32) are connected in series.

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