A coil for an inductive device, a method of winding a coil and an inductive device

Abstract

A coil for an inductive device is disclosed, comprising at least two winding layers formed of winding wire and at least two layers of dielectric material, wherein each winding layer is arranged on at least one layer of dielectric material, and each winding layer has a width which is less than the width of the coil, such that the winding layer only occupies a portion of the surface of the coil. The winding layer comprises a first end and a second end, the first end of the winding layer being substantially the first edge of the coil, and the second end terminating between the first edge and the second edge of the coil, the second end of the winding layer facing towards the second edge of the coil. At the second end of the winding layer, the winding wire extends towards the second edge of the coil and connects to the first end of the subsequent winding layer. The winding layers start alternately from opposite sides of the coil. This arrangement enables a significant reduction in the inductance and capacitance of the winding coil structure, thereby maximizing the resonant frequency of the primary winding coil structure. A method of winding such a coil and an inductive device comprising such a coil are also disclosed.

Description

Technical Field

[0001] This disclosure relates to a winding coil structure suitable for inductive devices such as voltage transformers or inductors, a method for winding such coils, and an inductive device comprising such coils. Background Technology

[0002] Voltage transformers (VTs) are a crucial component of electrical systems, tasked with precisely reducing high voltages to measurable levels for metering and protection purposes. A transformer structure comprises several key components: the core, frame, primary and secondary windings, and insulation. The core is typically made of laminated silicon steel sheets stacked together to form a magnetic circuit. The core acts as the medium for magnetic flux transmission, facilitating efficient energy transfer between the windings. The primary winding is the coil that receives energy from an external power source. In a transformer, the primary winding is connected to the input voltage source, whose alternating current generates a magnetic field. This magnetic field induces a voltage in the secondary winding, which is located adjacent to the primary winding, thus enabling energy transfer between the circuits. The voltage induced in the secondary winding depends on the turns ratio between the primary and secondary windings. In step-down medium-voltage transformers, the secondary winding has fewer turns and thicker wire compared to the primary winding, which has more turns and a thinner wire diameter. This design allows the secondary winding to handle larger currents at lower voltages, while the primary winding handles smaller currents at higher voltages. Insulating materials are used to electrically isolate the windings from each other and from the core, preventing short circuits and ensuring safe operation.

[0003] A choke is a type of inductor designed to block or "choke" high-frequency alternating current (AC) while allowing lower-frequency or direct current (DC) to pass through. It is widely used in power supplies, filters, and radio frequency (RF) circuits. A choke counteracts rapid changes in current by generating a magnetic field as current flows through it.

[0004] In existing technology, the standard structure of coils used in inductive devices (such as primary coils or choke coils in medium-voltage instrument transformers) employs an alternating assembly of multiple layers of winding wire and insulating material. Each layer is separated by insulating material to ensure dielectric withstand. The insulation typically has a porous structure and is usually made of specialized insulating tape, such as crepe paper or heat-upgraded kraft paper. The manufacture of such coils begins with winding several layers of insulating material onto a cylindrical frame. Next, a layer of winding made of fine wire is wound onto the insulating layer. Subsequently, multiple layers of insulating material and winding layers are wound in sequence, and finally, the coil is impregnated with epoxy resin under vacuum conditions and cured at high temperature.

[0005] This multi-layered structure results in a close arrangement of turns within each layer, creating significant capacitive coupling between the turns. The cumulative effect of these inter-turn capacitances, combined with the inherent inductance of the winding, determines its natural frequency, or resonant frequency. The natural frequency of a winding coil (also known as the self-resonant frequency, SRF, or primary resonant frequency) is the frequency at which the coil resonates due to the interaction between its inductance and inherent capacitance. Below the SRF, the coil primarily behaves as an inductor. At the SRF, inductive and capacitive reactance cancel each other out, resulting in a high impedance point. Above the SRF, the coil behaves more like a capacitor than an inductor. The natural frequency of the winding can be well approximated by the values ​​of lumped capacitance and lumped inductance. The capacitance in this configuration can be approximated by modeling each layer as a cylindrical capacitor, i.e., the capacitance value can be calculated as a series connection of multiple cylindrical capacitors. Each layer of turns represents a cylinder, and two adjacent layers separated by thin insulation form an interlayer capacitor. The interlayer capacitance value is directly proportional to the surface area of ​​the layer and inversely proportional to the interlayer distance—which is determined by the thickness of the insulation material. Therefore, as the number of layers (N) and the number of turns per layer (n) increase, the total capacitance of the winding increases. Simultaneously, the inductance of the coil is affected by the total number of turns and the coil's cross-sectional area; that is, the coil's equivalent inductance is proportional to the square of the number of turns and the coil's cross-sectional area. However, the inductance has a complex relationship with the layer width; generally, increasing the layer width (measured between the two furthest turns in a winding layer) leads to a decrease in inductance.

[0006] Achieving low lumped inductance and capacitance values ​​becomes challenging for coils with a very high number of turns. This difficulty results in lower resonant frequencies of the windings, which poses serious problems when metering parameters must be maintained well above the fundamental frequency. This issue is particularly pronounced when designing voltage transformers for power quality measurements in frequency ranges up to or even exceeding 20 kHz.

[0007] To address these challenges, various winding techniques have been explored. Known methods for increasing winding width involve using multiple parallel strands to wind the primary coil. While this method can reduce inductance, it also increases capacitance due to the increased surface area of ​​the conductor (copper winding layer), thus potentially negating the benefits of reduced inductance.

[0008] Known methods cannot overcome the aforementioned challenges and have many drawbacks. For example, they cannot adequately minimize the self-inductance and self-capacitance of multilayer primary windings. Summary of the Invention

[0009] The purpose of this invention is to overcome the aforementioned shortcomings of the prior art and to address the inherent limitations of conventional winding designs by introducing an innovative winding configuration that optimizes the reduction of inductance and capacitance. This invention proposes a winding structure that maximizes the resonant frequency, ensuring accurate performance in high-frequency applications.

[0010] This is achieved by providing a coil suitable for inductive devices, the coil comprising:

[0011] At least two winding layers formed by winding wires,

[0012] At least two layers of dielectric material, wherein each of the at least two winding layers is disposed on a layer of dielectric material.

[0013] The width of each of the at least two winding layers is smaller than the width of the coil, such that the winding layer occupies only a portion of the coil surface.

[0014] The winding layer includes a first end and a second end, wherein the first end of the winding layer is substantially at the first edge of the coil, and the second end of the winding layer terminates between the first edge and the second edge of the coil, and wherein the second end of the winding layer faces the second edge of the coil.

[0015] At the second end of the winding layer, the winding wire extends toward the second edge of the coil and connects to the first end of the next winding layer;

[0016] Furthermore, the winding layers begin alternately from opposite edges of the coil.

[0017] Preferably, the winding layers are separated by gaps.

[0018] Preferably, the dielectric material covers the areas above and below the winding layer, as well as the gap area.

[0019] Alternatively, the dielectric material may only cover the areas above and below the winding layer, thus leaving the gap empty.

[0020] Preferably, the second end of the winding layer extends to at most half the width of the coil.

[0021] Preferably, each winding layer has the same number of turns.

[0022] Alternatively, at least two winding layers may have different numbers of turns.

[0023] Preferably, the winding layer arranged on one side of the coil has a wider width than the winding layer arranged on the opposite side of the coil.

[0024] Preferably, the second end of the winding layer arranged on one side of the coil extends beyond half the width of the coil.

[0025] Preferably, the overlapping winding layers have decreasing numbers of turns.

[0026] The present invention also discloses a method for winding the above-mentioned coil, comprising the following steps:

[0027] a) A winding layer is formed by winding a layer of wire on a dielectric material, starting from one side edge of the coil, such that the width of the winding layer is less than the width of the coil, wherein the winding layer includes a first end and a second end, wherein the first end of the winding layer is substantially at the first edge of the coil, and the second end of the winding layer terminates between the first edge and the second edge of the coil, and wherein the second end of the winding layer faces the second end of the coil.

[0028] b) Lead the winding wire from the second end of the winding layer to the opposite edge of the coil and connect the winding wire to the first end of the next winding layer;

[0029] c) Arrange the dielectric material on the surface of the coil, including the winding layers and the remainder of the coil;

[0030] Step a) is executed at least twice, and steps b) and c) are executed at least once.

[0031] And step a) is repeated alternately from opposite edges of the coil.

[0032] When steps b) and c) are performed the same number of times as step a), the outermost winding layer is covered with dielectric material. When step c), or steps b) and c), are performed one less time than step a), the outermost winding layer is not covered with dielectric material.

[0033] Preferably, the second end of a winding layer is located at the position of the second end of the previous winding layer, so that the two successive winding layers do not overlap each other, and preferably a gap is left between them.

[0034] Preferably, in step c), the dielectric material is disposed only in the areas above and below the winding layer.

[0035] Preferably, the winding layers have different numbers of turns.

[0036] The present invention also discloses an inductor comprising the aforementioned coil, frame, and insulating housing. This inductor may be, for example, a transformer or a choke.

[0037] Advantages of this invention: This invention significantly reduces the inductance and capacitance of winding coil structures designed for inductive devices (e.g., medium-voltage transformers). Therefore, this invention maximizes the resonant frequency of the primary winding coil structure, thereby ensuring accurate performance of voltage transformers covering a frequency range up to 20 kHz and even exceeding 20 kHz. This invention ensures the desired inductance level is achieved without requiring excessive turns or layers. Therefore, it not only reduces capacitance but also maintains a compact and efficient transformer design. The proposed invention can be practically implemented using standard manufacturing processes without adding complexity. Manufacturing costs are reduced due to the use of fewer winding wires. Attached Figure Description

[0038] The present invention will be shown in more detail with reference to the accompanying drawings, in which:

[0039] Figure 1 The relationship between coil inductance and coil width is shown;

[0040] Figure 2 A cross-section of the coil winding layer according to the first embodiment is shown;

[0041] Figure 3 A cross-section of a coil winding layer according to a second embodiment is shown, wherein the gaps between the winding layers are filled with dielectric material;

[0042] Figure 4 A cross-section of a coil winding layer according to a third embodiment is shown, wherein the gaps between the winding layers are empty;

[0043] Figure 5 The cross-section of a coil winding layer with unequal number of turns is shown.

[0044] Figure 6 The cross-section of a coil winding layer with unequal turns in each winding layer, forming a trapezoidal shape, is shown.

[0045] Figure 7 A transformer comprising a coil according to the invention is shown;

[0046] Figure 8 The error curves of the standard VT winding and the winding according to the present invention are shown as a comparison. Detailed Implementation

[0047] Preferred embodiments of the present invention are described in detail below. For a proper understanding of this disclosure, corresponding elements or portions of the disclosure are indicated by the same reference numerals in the accompanying drawings in the following detailed description. These examples are for illustrative purposes only and do not limit the scope of the invention.

[0048] As mentioned above, the inductance of a coil depends on the total number of turns and the cross-sectional area of ​​the coil, and the inductance has a complex relationship with the width of the winding layers. Generally, increasing the layer width leads to a decrease in inductance. However, as the number of layers and the number of turns per layer increase, the total capacitance of the winding increases due to the expansion of the winding surface area.

[0049] Figure 1 The dependence of the calculated coil inductance on the coil layer width is shown. This layer width is measured between the two furthest turns, i.e., between the two opposite side edges of the coil. To obtain... Figure 1The results shown have a fixed number of layers (100), turns (1000), bobbin diameter (70 mm), dielectric insulation thickness (0.12 mm), and winding wire diameter (0.25 mm). The coil width (up to 90 mm) is increased by increasing the pitch (achieved through loose winding and / or the use of insulating spacers).

[0050] Assume a reference standard winding design for a voltage transformer comprises N layers, each separated by a dielectric material of thickness t. Each winding layer consists of n turns of winding wire, where the wire itself has a thickness d. The cumulative width of each winding layer, denoted by I, is determined by the number of turns n and the wire diameter d, and is expressed as: I = n × d. The total radial thickness R of the winding, called the radial width or diameter of the coil, includes the combined thickness of all layers and insulation material. This total radial width can be expressed as: R = N × (d + t). The inductance of a coil with a given total number of turns (n ​​× N) is significantly affected by the winding layer width, such as... Figure 1 As shown, increasing the layer width leads to a decrease in inductance. This inverse relationship is because a wider coil distributes the magnetic field over a larger volume, thereby reducing magnetic coupling between turns and thus lowering the inductance.

[0051] Therefore, increasing the winding width is advantageous in order to achieve lower inductance in the VT winding. To achieve both lower inductance and lower capacitance simultaneously, increasing the winding width is advantageous without excessively increasing the total surface area of ​​the winding.

[0052] This invention generally proposes a segmented or sectioned coil winding. The method divides the winding into multiple segments, with insulating material between each segment. Therefore, the width of a single winding layer is significantly smaller than the width of the coil. Consequently, it has fewer turns compared to a standard coil of the same width. By reducing the number of turns in each segment and increasing the physical spacing between turns, this method reduces inter-turn capacitance. Therefore, this invention can maximize the self-resonant frequency of the winding by reducing inductance and capacitance.

[0053] This is achieved by dividing the winding layer into alternating partial winding layers (e.g., half layers), such as... Figures 2 to 6 As shown. Each partial winding layer 1 occupies only a portion of the coil width W, where the width is measured from one edge of the coil to the other, i.e., between the two furthest turns of adjacent partial winding layers 1. In other words, a single winding layer 1 does not wrap around the coil from one edge to its opposite edge, but rather starts from one edge and extends only a portion of the coil width. For example, it extends at most to half the coil width W, and therefore is divided at most in the middle of that width W, as shown. Figure 2 and Figure 3As shown, however, the ratio of the coil width W to the width of the winding layer 1 may vary. Each winding layer 1 includes n turns of winding wire 2. At the level of a single winding layer 1, a portion of the coil width W thus contains a winding with n turns, while another portion of the coil width W contains a segment of the winding wire 2 that only partially wraps around the coil and reaches its opposite side edge, preferably not a full turn (e.g., 1 / 4 turn or even extending directly to the edge of the coil). However, the opposite side edge of the winding (coil) can be reached by one or several turns. The winding wire 2 is typically made of copper, but it is well known that the wire 2 can be made of any metal and alloy, or the wire 2 can be replaced by any conductor suitable for winding. Each end of the winding wire 2 has a terminal for connecting the winding, wherein the terminals are arranged so that they can be connected, and each (inner) layer of the winding wire 2 is arranged between two layers of dielectric material 3. In other words, one winding layer 1 is located in the first layer, and the other winding layer 1 is located in the second layer, separated by dielectric material 3.

[0054] In each embodiment, the winding layer 1 has a first end 1a and a second end 1b, wherein the first end 1a of the winding layer 1 is essentially the first edge of the coil, and the second end 1b of the winding layer 1 terminates between the first and second edges of the coil. The second end 1b of the winding layer 1 faces the second edge of the coil. Therefore, each portion of the winding layer 1 begins from one side edge of the coil and extends toward the center of the coil. At this location, the winding pauses, and the winding wire 2 is led to the opposite side edge of the coil (in the layer level of that winding layer). In other words, the winding wire 2 extends toward the second end of the coil and connects to the first end 1a of the next winding layer 1. For example, the winding wire 2 is led to the opposite side edge in a quarter turn. Therefore, the remaining portion of the coil width W (through which this segment of the winding wire 2 is led to the opposite side edge of the coil) does not contain the winding layer 1. This remaining portion is filled with a dielectric material 3. The thickness of the dielectric filling material 3 can be close to the diameter of the winding wire 2, for example, having the same thickness, such that the two portions of the entire layer have approximately the same thickness. More preferably, the thickness of the dielectric material 3 is less than the diameter of the winding wire 2. In one example, the thickness of the winding wire 2 may be 0.25 mm, while the thickness of the dielectric material 3 layer may be 0.1 mm. Here, the entire layer includes a portion of the winding layer 1 and a portion containing the winding wire 2 extending to the end of the coil. The dielectric material 3 is also arranged below the first (I) portion of the winding layer 1, closest to the coil frame—therefore, the innermost winding layer 1 is arranged above the dielectric material 3 layer. In all embodiments, each inner winding layer 1 is arranged between two layers of dielectric material 3, while the outermost winding layer 1 may be covered or uncovered by the dielectric material 3. Thus, each winding layer 1 is arranged on at least one layer of dielectric material 3. This forms a sandwich structure in which the inner winding layer 1 is also covered by the upper dielectric material 3, while the last (outermost) winding layer 1 may also be covered by the dielectric material 3 or remain uncovered. Figures 2 to 6 In this configuration, the outermost winding layer 1 is not covered by the dielectric material 3. Clearly, in all embodiments, the outermost winding layer 1 may terminate at its second end 1b, where the winding wire 2 is not led to the opposite edge of the coil, as... Figures 2 to 6 As shown. Alternatively, winding wire 2 can be led to a point on the opposite side edge of the coil or on its surface.

[0055] First embodiment of the present invention, for example Figure 2 As shown. Figure 2 A cross-section of the coil winding is shown, wherein each partial winding layer 1 comprises n turns of winding wire 2. The coil comprises N alternating partial winding layers 1, for example, 100 layers. For clarity, Figure 2 Only six winding layers 1 are shown, numbered I, II, III, IV, V, and VI. Each partial winding layer 1, such as the first winding layer (I), begins at its first end 1a (basically the edge of the coil) and extends towards its center. Therefore, in Figure 2 In the illustrated embodiment, the winding wire 2 is wound substantially to the center of the coil. In this embodiment, each winding layer 1 thus pauses at the center of the coil. Therefore, the width of a portion of the winding layer 1, i.e., the width of the winding in each winding layer 1, is substantially half the width W of the coil. When the second end 1b of the portion of the winding layer 1 is reached, the wire 2 is led to the opposite side edge of the coil. The entire layer comprises two parts: the portion containing the winding layer 1, and the remaining portion of the winding wire 2 led to the opposite side edge of the coil. The winding layer 1 and the portion containing only the wire segment led to the opposite side edge are covered with dielectric material 3. In other words, the entire surface of the coil is covered with dielectric material 3. Then, the next layer (II) is wound from this opposite side edge of the coil, starting at its first end 1a. When the winding layer 1 of the second layer (II) reaches its end 1b, the wire 2 is led from the second end 1b to the previous (first) edge of the coil. Similarly, the entire surface of the coil, i.e., winding layer 1 and the portion containing only the wire segments led to the edge, is covered with dielectric material 3. This process continues until the required number of partial winding layers 1 are reached, containing the required total number of turns n. As a result, the entire coil width W contains two interconnected winding segments. In each layer, one part has windings, and the other part does not have windings but contains winding wires 2 led to the edge of the coil. To avoid forming bulges on the coil, the first winding layer 1 (I) should not overlap with the subsequent second winding layer 1 (II), the third winding layer 1 (III) should not overlap with the subsequent fourth winding layer 1 (IV), and so on. In the first embodiment, each winding layer 1 has the same width. Therefore, the width W of the coil is essentially equal to twice the width of the winding layer 1 (I), possibly with a small offset due to the offset of the dielectric material 3 and / or due to loose windings and / or the use of insulating spacers: W ≈ 2 x n x d ≈ 2 x I).

[0056] Second embodiment of the invention, for example Figure 3 As shown. Figure 3 A cross-section of the coil winding is also shown, where each partial winding layer 1 includes n turns of winding wire 2. The coil comprises N alternating partial winding layers 1, for example, 100 layers. For clarity, Figure 3 Only six winding layers 1 are shown, numbered I, II, III, IV, V, and VI. Each partial winding layer 1 also has a first end 1a and a second end 1b, for example, the first winding layer (I), which starts from the winding edge that serves as the edge of the coil and extends towards its center. However, in this embodiment, the winding of each winding layer 1 does not extend to the center of the coil. In contrast to the first embodiment, the width of the partial layer 1, i.e., the width of the winding in each winding layer 1, is less than half the width W of the coil. This results in a gap 4 between the alternating partial winding layers 1. The gap 4 is defined by the distance between the nearest turns (second ends 1b) in adjacent winding layers 1 (I and II, II and III, III and IV, IV and V, etc.). An electric field exists in this gap 4. When the end of the partial winding layer 1 is reached (this end is located before the center of the coil), the winding wire 2 is led to the opposite side edge of the coil. Therefore, the entire total layer includes the portion containing the winding layer 1 and the remaining portion of the wire 2 led to the opposite side edge of the coil.

[0057] exist Figure 3 In the illustrated embodiment, the remaining portion of the winding layer 1 and the winding wires 2 leading to opposite edges of the coil are covered by dielectric material 3. Therefore, dielectric material 3 covers the entire width of the coil, i.e., the entire surface of the coil.

[0058] In another embodiment, such as Figure 4 As shown, the dielectric material 3 only covers the area occupied by the winding layer 1. In this case, it only covers the areas above and below the winding layer 1, leaving the sections of the unwound wire 2 unfilled by the dielectric material 3, thus keeping some of the gaps 4 between the winding layers 1 empty. Figure 4 In the middle, gap 4 is located in the central region of the coil. Similar to the first embodiment, the next winding layer 1 (II) following the previous winding layer 1 (I) begins from the opposite side edge of the coil. When the winding of the second winding layer 1 (II) reaches the designated position (in Figure 4In the illustrated embodiment, the winding wire 2 is led to the edge of the previous (first) coil (far before reaching the center of the coil). Similarly, the surface of the coil, i.e., the portion containing the winding and only the section containing the wire 2 led to the edge, is covered with dielectric material 3. This process continues until the desired number of partial winding layers 1 are reached, containing the required total number of turns n. As a result, the entire coil width W comprises two interconnected winding layer 1 sections with a gap 4 between them. In this embodiment, similarly, the width of the coil is equal to twice the width of the winding (I) plus the width (g) of the gap 4: W ≈ 2 x n x d + g ≈ 2 x I + g).

[0059] In summary, one winding layer 1 (I) and the remaining portion of the winding wire 2 led to the side of the coil are arranged between the first and second layers of dielectric material 3; another winding layer 1 (II) and the remaining portion of the winding wire 2 are arranged between the second and third layers of dielectric material 3; another winding layer 1 (III) and the remaining portion of the winding wire 2 are arranged between the third and fourth layers of dielectric material 3, and so on. Each layer of dielectric material 3 includes a gap 4, which may or may not be filled by dielectric material 3.

[0060] In another embodiment, the number of turns n in some winding layers 1 (layers stacked or arranged opposite each other) is not equal, therefore the ratio of the number of turns n in adjacent winding layers 1 is not as shown. Figure 2 , Figure 3 and Figure 4 50 / 50 shown.

[0061] An example of such an implementation Figure 5 As shown. Here, one winding layer 1 (I) extends beyond the center of the coil, while the next winding layer 1 (II) does not reach the center of the coil. Therefore, the winding layers 1 (e.g., I, III) arranged on one side of the coil have a larger width (I1) than the winding layers 1 arranged on the opposite side of the coil (e.g., II, IV). Dielectric material 3 is disposed between the winding layers 1 in a manner similar to that described in the previous embodiment. Figure 5 In this configuration, the ratio of the number of turns n between adjacent winding layers 1 (I and II; III and IV; etc.) is 9:8. In this case, a gap 4 can also be provided, and the gap 4 can be filled with dielectric material 3 or left unfilled. In another variation, neither of the two winding layers 1 reaches the center of the coil, wherein adjacent (opposite) winding layers 1 have different numbers of turns.

[0062] Another embodiment in which the number of turns n in alternating partial winding layers 1 is not equal, for example Figure 6As shown. In this case, consecutive sub-layers, i.e., winding layers 1 (I and III; II and IV; etc.) stacked on top of each other, do not have equal numbers of turns n. In this case, the coil can have a non-square shape, such as a trapezoidal shape, as shown. Figure 6 As shown. Here, winding layer 1 (I) has more turns than winding layer 1 (III), winding layer 1 (II) has more turns than winding layer 1 (IV), and so on. The trapezoidal shape is achieved by reducing the number of turns in the winding layers 1 that are stacked on top of each other. In this case, a gap 4 is also provided, and the gap 4 may be filled with dielectric material 3 or left unfilled.

[0063] As the distance between adjacent winding layers 1—which is determined by the width of the gap 4 between them—increases, the width W of the entire coil can also increase (while maintaining the same number of turns n becomes possible). This allows for further reduction in capacitance.

[0064] Another benefit of gap 4 is that, during the casting process, epoxy resin fills the gap 4 between the sections, reducing the risk of potential porosity and better impregnating all edges of the winding. Furthermore, keeping gap 4 empty (without dielectric material 3) further facilitates epoxy resin filling.

[0065] When the coil includes gap 4, its width can, for example, be similar to the diameter of the winding wire 2. There is no upper limit to the width of gap 4. A larger gap 4 allows for a further increase in the width of the coil. For example, the gap can even be as wide as 50 mm or more.

[0066] The diameter of the skeleton is, for example, 20 mm to 350 mm.

[0067] The width of winding wire 2 is, for example, 0.1 mm to 1 mm.

[0068] Dielectric materials include, for example, PET film (polyester film), Trivolton, paper, and PTFE.

[0069] The number of turns n in winding layer 1 is, for example, 100 to 500.

[0070] The thickness of dielectric material 3 is, for example, 0.05 mm to 0.3 mm.

[0071] The number of dielectric layers 3 arranged below or above the winding layer 1 is at least one, but may be more, such as two or three layers of dielectric material 3.

[0072] The coil's frame can have various shapes, as its shape does not affect the function of the invention—for this reason, the frame is not depicted in the accompanying drawings. The frame can be, for example, cylindrical, annular, elliptical, rectangular, or other polygonal shapes.

[0073] Another aspect of the invention is a method for winding a coil, which can realize, but is not limited to, the winding design described in the above embodiments. The method includes the following steps: winding a layer of winding wire 2 on a dielectric material 3 to form a winding layer 1, such that the width of the winding layer 1 is less than the width W of the coil (not reaching the opposite end of the coil), thereby forming a partial winding layer 1; guiding the winding wire 2 through the remaining portion of the coil to the opposite side edge of the coil; and arranging the dielectric material 3 above the winding layer 1 and above the remaining portion of the coil. After arranging the dielectric material 3 on the surface of the coil, the first step is repeated starting from the edge of the coil to which the winding wire 2 is led (i.e., the opposite side edge). That is, the winding wire 2 is wound around the dielectric material 3, up to the position reached by the previous winding layer 1, and from that position, the winding wire 2 is led to the edge of the coil. Similarly, dielectric material 3 is provided above the winding layer 1 and above the portion of the coil where the winding layer 1 is missing. The steps are repeated until the desired number of winding layers 1 are reached. Successive winding layers 1 should be arranged so as not to overlap to avoid bulging on the coil surface. The final step of arranging the dielectric material 3 above the winding layer 1 can be performed the same number of times as the steps of winding a layer of winding wire 2 on the dielectric material 3 and guiding the winding wire 2 to the opposite edge of the coil, thus forming a structure in which the outermost winding layer 1 is covered by the dielectric material 3. Alternatively, the final step of arranging the dielectric material 3 above the winding layer 1 can be performed one less time than the previous steps, thus forming a structure in which the outermost winding layer 1 is exposed (not covered by the dielectric material 3). In the latter case, obviously, the step of guiding the winding wire 2 to the opposite edge of the coil can also be performed one less time than the step of winding a layer of winding wire 2 on the dielectric material 3, thus obtaining the following result: Figures 2 to 6 The structure shown.

[0074] This method allows for the provision of a gap 4 between winding layers 1, as described above with reference to the coil structure. In this case, the method includes the following steps: winding a layer of winding wire 2 onto a dielectric material 3 to form a winding layer 1 such that the winding layer 1 does not reach the opposite ends of the coil, thus forming a partial winding layer 1; guiding the winding wire 2 to the opposite side edges of the coil; and arranging the dielectric material 3 above the winding layer 1 and above the remaining portion of the coil. After arranging the dielectric material 3 on the coil surface, the winding wire 2 is wound into a coil to form another winding layer 1, wherein this winding layer 1 ends before reaching the end of the previous winding layer 1, leaving a gap 4 between them, and then the winding wire 2 is again guided to the edge of the coil. Similarly, the dielectric material 3 is arranged above the winding layers and the portion of the coil lacking winding layers 1. The steps are repeated until the desired number of winding layers 1 are reached. The distance between the nearest turns of adjacent winding layers 1 starting from opposite side edges defines the gap 4.

[0075] The dielectric material 3 may cover the entire surface of the coil, including the gap 4. Alternatively, the dielectric material 3 may be disposed only in the area of ​​the winding layer 1, thereby leaving the gap 4 empty.

[0076] This method may include providing a different number of turns n for each winding layer 1. In one example, it may include providing the same number of turns n in each winding layer 1. In another example, it may include providing different numbers of turns n in winding layer 1, as shown in the reference. Figure 4 and Figure 5 The number of turns may differ in adjacent layers 1 (starting from opposite sides of the coil) arranged opposite each other and / or in subsequent layers 1 stacked on top of each other (starting from the same side of the coil).

[0077] In another aspect, the present invention discloses an inductor comprising a coil according to the invention. The inductor may be, for example, a transformer or a choke.

[0078] Figure 7 A transformer is depicted, comprising at least two coils and a frame 7 arranged within said at least two coils, the coils being a primary coil 5 and a secondary coil 6. The primary coil 5 is a coil according to the invention. The frame 7 is mounted on an iron core 8. The coils 5 and 6 may be arranged in a dielectric casting body, for example, made of a dielectric material. The material should have sufficient dielectric strength. In one embodiment, the transformer is a medium-voltage transformer. During the casting process, the transformer may be embedded in epoxy resin. In an embodiment where a gap 4 is provided, the epoxy resin fills the gap 4 between the winding layers 1.

[0079] In the case where the inductive device is a choke, it includes a coil according to the invention and a dielectric casting, such as an epoxy resin or plastic housing.

[0080] Figure 8 A comparison of error curves is shown for a standard VT winding (solid line) and a partially layered winding according to the invention (dashed line). Both VTs have the same frame and number of turns. In the case of the standard winding, the secondary voltage (measured value) decreases as the frequency approaches the resonance of the first internal winding. This internal winding resonance is closely related to the inherent resonance of the winding. Increasing the inherent frequency of the winding also increases the frequency of the first internal winding resonance, which manifests as a smaller negative amplitude error in the case of the winding according to the invention.

[0081] List of reference numerals in the attached diagram:

[0082] 1-Winding layer

[0083] 2-Winding wires

[0084] 3-Dielectric Materials

[0085] 4-gap

[0086] 5- Primary coil

[0087] 6-Secondary coil

[0088] 7-Skeleton

[0089] 8-Iron Core

Claims

1. A coil suitable for inductive devices, comprising: At least two winding layers (1) formed by winding wires (2), At least two layers of dielectric material (3), wherein each of the at least two winding layers (1) is disposed on at least one layer of dielectric material (3). The width of each of the at least two winding layers (1) is smaller than the width of the coil, such that the winding layer (1) occupies only a portion of the coil surface. The winding layer (1) includes a first end (1a) and a second end (1b), wherein the first end (1a) of the winding layer (1) is substantially the first edge of the coil, and the second end (1b) of the winding layer (1) terminates between the first edge and the second edge of the coil, wherein the second end (1b) of the winding layer (1) faces the second edge of the coil. At the second end (1b) of the winding layer (1), the winding wire (2) extends toward the second edge of the coil and connects to the first end (1a) of the next winding layer (1); Each winding layer (1) starts alternately from the opposite two edges of the coil.

2. The coil according to claim 1, wherein, Each winding layer (1) is separated by a gap (4).

3. The coil according to claim 2, wherein, The dielectric material (3) covers the area above and below the winding layer (1) and the area of ​​the gap (4).

4. The coil according to claim 2, wherein, The dielectric material (3) covers only the area above and below the winding layer (1), thus keeping the gap (4) empty.

5. The coil according to any one of the preceding claims, wherein, The second end (1b) of the winding layer (1) extends to at most half the width of the coil.

6. The coil according to any one of the preceding claims, wherein, Each winding layer (1) has the same number of turns.

7. The coil according to any one of claims 1 to 5, wherein, At least two winding layers (1) have different numbers of turns.

8. The coil according to claim 7, wherein, The width of the winding layer (1) arranged on one side of the coil is greater than the width of the winding layer (1) arranged on the opposite side of the coil.

9. The coil according to claim 7, wherein, The second end (1b) of the winding layer (1) arranged on one side of the coil extends beyond half the width of the coil.

10. The coil according to claim 7, wherein, The overlapping winding layers (1) have decreasing turns.

11. A method for winding a coil according to any one of claims 1 to 10, comprising the following steps: a) Starting from one edge of the coil, a layer of winding wire (2) is wound on the dielectric material (3) to form a winding layer (1) such that the width of the winding layer (1) is less than the width of the coil, wherein the winding layer (1) includes a first end (1a) and a second end (1b), wherein the first end (1a) of the winding layer (1) is substantially the first edge of the coil, and the second end (1b) of the winding layer (1) terminates between the first edge and the second edge of the coil, wherein the second end (1b) of the winding layer (1) faces the second end of the coil; b) Guide the winding wire (2) from the second end (1b) of the winding layer (1) toward the opposite side edge of the coil and connect the winding wire (2) to the first end (1a) of the next winding layer (1); c) Arrange the dielectric material (3) on the surface of the coil; Step a) is executed at least twice, and steps b) and c) are executed at least once. Step a) is repeated alternately from opposite edges of the coil.

12. The method according to claim 11, wherein, The second end (1b) of a winding layer (1) is located at the position of the second end (1b) of the previous winding layer (1), so that the two successive winding layers (1) do not overlap each other, and preferably a gap (4) is left between them.

13. The method according to claim 12, wherein, In step c), the dielectric material (3) is arranged only in the area above and below the winding layer (1).

14. The method according to any one of claims 11 to 13, wherein, Each winding layer (1) has a different number of turns.

15. An inductor comprising a frame, an insulating housing, and a coil according to any one of claims 1 to 10.

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