Foil winding lead and method of forming same

Abstract

The present invention relates to an insulated winding assembly comprising: an insulated foil conductor comprising a lead-in section, a lead-out section, and a winding section located between the lead-in section and the lead-out section, in which winding section the insulated foil conductor is wound on a core material to form a winding, wherein each of the lead-in section and the lead-out section is folded relative to the winding section and arranged transversely to the winding of the winding section, and wherein each of the lead-in section and the lead-out section comprises at least one folding cut along the length direction of the foil conductor, thereby forming at least two strips. The invention further provides a corresponding method and a transformer comprising the winding assembly.

Description

Technical Field

[0001] The present disclosure relates generally to the field of electrical devices and, more particularly, to foil winding leads, such as used in transformers and inductors, and methods of forming the same. Background Art

[0002] With the rapid growth in the number of high-power low-voltage DC loads and sources in recent years, the demand for an efficient interface between the medium-voltage (MV) AC grid and the low-voltage (LV) DC bus has increased significantly.

[0003] In this context, so-called solid-state transformers (SSTs), electrically isolated high-power AC / DC and DC / DC converters, can replace the existing technology based on low-frequency transformers (LFTs) due to their advantages such as smaller size and lighter weight.

[0004] Power conversion in SSTs is supported by transformers operating with MV pulse width modulation (PWM) waveforms in the kilohertz range. Therefore, such transformers are called medium frequency transformers (MFT), see Figure 1 .

[0005] The coil of a typical MFT consists of an inner secondary winding (LV) connected to the low voltage side of the converter (<1.1kV) and a primary winding (HV) radially stacked to the LV and connected to the outer side of the converter where the voltage is highest. The coil is mounted around the magnetic circuit of the MFT which is usually grounded for safety. Figure 2 The upper half of the MFT cross section is shown.

[0006] The use of foil conductors for winding MFT has attracted interest due to lower costs compared to litz wire. The two main limitations of using foil conductors are the ohmic losses that occur in the case of magnetic fields perpendicular to the conductors and the manufacturing complexity of realizing the winding leads (busbars) in the case of large windings and wide foils.

[0007] As shown in the patents described in the next section, a variety of methods have been found to achieve the lead-out of foil windings. Figure 3 An example of using 50 mm foil winding leads is shown. In this case, the foil can be easily folded, as shown in Figure 3 In high power MFT, the foil may exceed 200 mm, so Figure 3 The method shown is not practical.

[0008] US 2009 / 0302986 discloses an idea involving a busbar implementation, however, its main drawback is the reduction in the conductor cross-sectional area corresponding to the lead wires.

[0009] US 7880575 B2 proposes to realize the busbar by welding a layer of conductor. This does not result in a monolithic structure.

[0010] US2002 / 0057177 proposes some improvements, in which the winding wires are mechanically separated from the windings so that there is an electrical connection. It also proposes to reduce the cross-sectional area of ​​the conductor.

[0011] No method has been found to reduce the ohmic losses in the MFT busbars. Summary of the invention

[0012] The following is a summary of aspects of some examples disclosed herein. It should be understood that these aspects are only intended to provide the reader with a brief overview of these specific embodiments and are not intended to limit the scope of the present disclosure. In fact, the present disclosure may encompass various aspects and / or combinations of aspects that may not be listed.

[0013] In a first aspect of the present disclosure, an insulated winding assembly is proposed, comprising an insulated foil conductor, the insulated foil conductor comprising an introduction section, a lead-out section and a winding section located between the introduction section and the lead-out section, wherein, in the winding section, the insulated foil conductor is wound on a core material to form a winding, wherein each introduction section and the lead-out section are folded relative to the winding section and transverse to the winding arrangement of the winding section, and wherein each introduction section and the lead-out section include at least one folding cut (folding cut) along the length direction of the foil conductor, thereby forming at least two strips.

[0014] Foil conductors are well known to those skilled in the art and are formed of an insulated planar conductor. The core material may be any material suitable for the application. For example, the core material may be air, or any suitable ferromagnetic material with a suitable magnetic field conductivity.

[0015] The inventors believe that by forming at least one folding cut in the foil conductor and folding the at least two strips formed in this way in the transverse direction of the winding, the surface area exposed to the magnetic field in the direction perpendicular to the magnetic field can be reduced. This has the advantage of reducing the losses caused by eddy currents.

[0016] One advantage of the present disclosure compared to the known prior art documents is that lower losses are achieved without reducing the cross-sectional area of ​​the conductor. Therefore, this ensures a higher current carrying capacity. Another advantage of the present disclosure is that the winding assembly can be formed without any mechanical connection (such as welding) between different elements. Therefore, the winding assembly is formed in one piece, ensuring a higher current carrying capacity and lower losses caused by eddy currents. According to an example, the at least two strips are stacked on top of each other. This can be achieved, for example, by folding the at least two strips in a suitable manner so that they can be stacked together.

[0017] According to one example, the insulated winding assembly further comprises a plurality of slits formed in at least two strips in the lead-in section and the lead-out section, wherein the plurality of slits are formed along the length direction. The inventor believes that by providing more slits on the strips thus formed, eddy currents can be further limited.

[0018] According to one example, the insulated winding assembly further comprises lugs located in each lead-in section and lead-out section, and these lugs are arranged to provide electrical connection of the insulated winding assembly with external electrical components. These lugs can be connected to each of the at least two strips, or can be connected to a stack formed by stacking the at least two strips on top of each other.

[0019] According to an example, each of the at least two strips has an equal width. The embodiment in which each of the at least two strips has an equal width is a preferred embodiment. This ensures a uniform current distribution on each strip.

[0020] According to one example, the at least two strips have different lengths so that after folding, the at least two strips end at the same line. This can be achieved by, for example, cutting off a small portion of each subsequent strip so that the strips perfectly overlap each other. A person skilled in the art will appreciate that such a choice facilitates connecting the winding assembly to other components.

[0021] In a second aspect of the present disclosure, a power transformer is provided, comprising a primary winding and a secondary winding, wherein at least one of the primary winding or the secondary winding is an insulated winding assembly according to any example of the first aspect of the present disclosure. Specifically, such a winding assembly can be used in a solid-state transformer that is increasingly popular in power converters.

[0022] It should be further pointed out that the definitions and advantages of the first aspect of the present disclosure as an insulated winding assembly are also relevant to the second aspect of the present disclosure as a power transformer.

[0023] In a third aspect of the present disclosure, a method for forming an insulated winding assembly is proposed, wherein the insulated winding assembly is formed using a foil conductor having a lead-in section, a lead-out section, and a winding section located between the lead-in section and the lead-out section, the method comprising the following steps: providing at least one folding cut along the length direction of the foil conductor to form at least two strips in each of the lead-in section and the lead-out section of the foil conductor; winding the winding section on a core material; and folding each of the lead-in section and the lead-out section transversely to the winding section.

[0024] It should be noted that the definitions and advantages of the first aspect of the present disclosure being an insulated winding assembly are also relevant to the third aspect of the present disclosure being a method of forming an insulated winding assembly.

[0025] According to an example of the third aspect, after folding, the at least two strips are stacked on top of each other.

[0026] According to an example of the third aspect, the method further includes the step of forming a plurality of slits in each of the at least two strips in the lead-in section and the lead-out section, wherein the plurality of slits are formed along the length direction.

[0027] According to an example of the third aspect, the method further comprises the step of providing a terminal lug in each of the lead-in section and the lead-out section to provide electrical connection between the insulated winding assembly and an external electrical component.

[0028] According to an example of the third aspect, the folding cut is arranged so that each of the at least two strips has the same width.

[0029] According to an example of the third aspect, the at least two strips have different lengths, so that after folding, the at least two strips end at the same line.

[0030] The present disclosure is described in conjunction with the accompanying drawings. It should be emphasized that, in accordance with industry standard practice, various features are not drawn to scale. In fact, for the sake of clarity of discussion, the size of various feature structures may be arbitrarily increased or decreased.

[0031] In the accompanying drawings, similar components and / or features may have the same reference label. If only the first reference label is used in the specification, the description is applicable to any similar component having the same first reference label regardless of the second reference label.

[0032] The above and other aspects of the present disclosure will be apparent from and elucidated with reference to the embodiments described hereinafter. BRIEF DESCRIPTION OF THE DRAWINGS

[0033] Figure 1 A medium frequency transformer MFT with foil conductors (prior art) is shown.

[0034] Figure 2 A cross section is shown indicating the primary and secondary windings of a transformer (prior art).

[0035] Figure 3 A 50 mm foil conductor MFT prototype is shown where the busbars are folded over to form the leads of the winding (prior art).

[0036] Figure 4 One aspect of the present disclosure using a paper foil is shown.

[0037] Figure 5 The concept of the present disclosure as applied to a transformer is shown. DETAILED DESCRIPTION

[0038] A more detailed description will be given with reference to specific examples, some of which are illustrated in the accompanying drawings so that the features of the present disclosure may be understood in more detail. It should be noted that the drawings illustrate only typical examples and therefore should not be considered to limit the scope of the subject matter of the claims. The drawings are incorporated to facilitate understanding of the present disclosure and are not necessarily drawn to scale. The advantages of the subject matter of the claims will become apparent to those skilled in the art upon reading the description in conjunction with the drawings.

[0039] The following description provides only preferred exemplary embodiments and is not intended to limit the scope, applicability or configuration of the present disclosure. Specifically, the following description of the preferred exemplary embodiments will provide a feasible description of the preferred exemplary embodiments of the present disclosure for those skilled in the art, and it should be understood that various changes may be made to the functions and arrangements of the elements, including combinations of features in different embodiments, without departing from the scope of the present disclosure.

[0040] Unless the context clearly requires otherwise, throughout the specification and claims, the words "include", "comprises", and the like are to be interpreted in an inclusive sense, and not in an exclusive or exhaustive sense; that is, in the sense of "including but not limited to". As used herein, the terms "connected", "coupled", or any variation thereof, represent any connection or coupling between two or more elements, whether direct or indirect; the coupling or connection between elements may be physical, logical, electromagnetic, or a combination thereof. In addition, when the words "herein", "above", "below", and words of similar meaning are used in this application, they refer to the entire application and not to any particular part of this application. Where the context permits, words used in the singular or plural in the detailed description may also include the plural or singular, respectively. When referring to a list of two or more items, the word "or" encompasses all of the following interpretations of the word: any item in the list, all items in the list, and any combination of items in the list.

[0041] These and other changes can be made to the technology according to the detailed description below. Although the specification describes certain examples of the technology and describes the expected best mode, no matter how detailed the description seems, the technology can be practiced in a variety of ways. The details of the system may vary greatly in its specific implementation, but are still included in the technology disclosed herein. As mentioned above, specific terms used when describing certain features or aspects of the technology should not be understood to imply that the term is redefined here to be limited to any specific feature, characteristic, or aspect of the technology associated with the term. In general, the terms used in the following claims should not be interpreted as limiting the technology to the specific examples disclosed in the specification unless such terms are explicitly defined in the detailed description section. Therefore, the actual scope of the technology covers not only the disclosed examples, but also all equivalent ways of practicing or implementing the technology according to the claims.

[0042] Figure 1-3 References have been cited and explained in the background technology section. Figure 4 and 5 The invention according to the present application is further explained.

[0043] Figure 4 One aspect of the present disclosure using paper foil is shown. It will be appreciated that Figure 4 The entire foil conductor is not shown, but only a portion of the foil conductor is shown. It is understood that Figure 4 A section of the foil conductor starting from the lead-in section is shown, wherein the folding cut is shown and the folding position is transverse to the winding of the winding section. The winding itself is not shown, nor is the lead-out section.

[0044] A person skilled in the art will appreciate that a similar configuration can be obtained at the other end of the foil conductor to obtain a lead-out section. Furthermore, according to the present disclosure, the main purpose of the present invention is to reduce the losses in the MFT busbar, which is achieved by folding the cutouts and folding the lead-in section and / or the lead-out section, which is achieved in Figure 4 The foil busbar is realized by cutting the conductor, as shown in (1). The resulting strip is folded, as shown in (2). The individual conductors are insulated from each other. The foil is cut into several vertical cuts (3). The following benefits are achieved:

[0045] Compared with the ideas proposed in the prior art, the cross-sectional area of ​​the conductor is not reduced

[0046] No welding required – contrary to the ideas proposed in known prior art literature

[0047] The surface through which the normal magnetic field passes is reduced. The proximity losses in the conductor are reduced. The results have also been confirmed by the same numerical model verified experimentally.

[0048] The slits (3) further reduce the circulating currents caused by the normal magnetic field.

[0049] although Figure 4 It is suggested to make 3 fold cuts to obtain 4 strips, but those skilled in the art understand that this is for demonstration purposes only. In actual situations, the number of cuts can be increased or decreased based on the desired application or any other constraints. In addition, Figure 4 (1) in the figure shows that each strip formed in this way has a different length. This ensures that after folding, each strip overlaps each other so that all strips end at the same line, as shown in (2) and (3). This facilitates connecting the lead-in section and / or lead-out section with other electrical components in a simple manner.

[0050] Figure 5 The concept of the present disclosure as applied to a transformer is shown.

[0051] Detail 1: Cut the foil conductor into four sections or strips and fold them 90° relative to the foil axis;

[0052] Detail 2: Each winding lead (in and out) is cut into nine slits, corresponding to areas of high transverse magnetic field;

[0053] Detail 3: Each lead has a hole at the end for electrical connection to the lugs of an external cable - this is optional.

[0054] although Figure 5 It is suggested to implement four segments or strips and provide nine slits in the strips, but those skilled in the art will appreciate that these are merely exemplary and not limiting in any way.

Claims

1. An insulated winding assembly, comprising: An insulated foil conductor comprises a lead-in section, a lead-out section and a winding section located between the lead-in section and the lead-out section, wherein in the winding section, the insulated foil conductor is wound on a core material to form a winding, wherein each of the lead-in section and the lead-out section is folded relative to the winding section and arranged transversely to the winding of the winding section, and wherein each of the lead-in section and the lead-out section comprises at least one folded cut along the length direction of the foil conductor, thereby forming at least two strips.

2. The insulated winding assembly according to claim 1, wherein: The at least two strips are stacked one on top of the other.

3. The insulated winding assembly according to any one of the preceding claims, further comprising a plurality of slits formed in each of the at least two strips in the lead-in section and the lead-out section, wherein the plurality of slits are formed along a length direction.

4. The insulated winding assembly according to any one of the preceding claims, further comprising a lug in each of the lead-in section and the lead-out section, the lug being arranged to provide electrical connection of the insulated winding assembly to an external electrical component.

5. An insulated winding assembly according to any one of the preceding claims, wherein: Each of the at least two strips has the same width.

6. An insulated winding assembly according to any one of the preceding claims, wherein: The at least two strips have different lengths such that after folding, the at least two strips terminate at the same line.

7. A power transformer comprising a primary winding and a secondary winding, wherein: At least one of the primary winding or the secondary winding is an insulated winding assembly according to any one of claims 1-6.

8. A method of forming an insulated winding assembly, wherein: The insulated winding assembly is formed using a foil conductor having a lead-in section, a lead-out section, and a winding section located between the lead-in section and the lead-out section, and the method comprises the following steps: - providing at least one folding cut along the length direction of the foil conductor, thereby forming at least two strips in each of the lead-in section and the lead-out section of the foil conductor; - winding the winding segments onto a core material; - and folding each of the lead-in and lead-out segments transversely to the winding of the winding segment.

9. The method according to claim 8, wherein: After folding, the at least two strips are stacked on top of each other.

10. The method according to any one of claims 8-9, further comprising the following steps: A plurality of slits are formed in each of the at least two strips in the lead-in section and the lead-out section, wherein the plurality of slits are formed along a length direction.

11. The method according to any one of claims 8 to 10, further comprising the following steps: A terminal lug is disposed in each of the lead-in section and the lead-out section to provide electrical connection between the insulated winding assembly and an external electrical component.

12. The method according to any one of claims 8 to 11, wherein: The folding cut is provided so that each of the at least two strips has the same width.

13. The method according to any one of claims 8 to 12, wherein: The at least two strips have different lengths such that after folding, the at least two strips terminate at the same line.

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