Coil arrangement with reduced losses and stabilized coupling factor and system for wireless energy transmission

Abstract

A coil arrangement with reduced losses and a stabilized coupling factor is specified. The arrangement has a coil core and a first winding whose turns are distributed across several spaced-apart sections.

Description

[0001] The invention relates to a coil arrangement with reduced losses and a stabilized coupling factor, such as can be used in systems for wireless energy transmission, and corresponding systems for wireless energy transmission.

[0002] Systems for the wireless transmission of energy, such as electrical energy, typically have a primary coil arrangement and a secondary coil arrangement. A time-varying magnetic field is emitted by the primary coil arrangement and received by the secondary coil arrangement. The primary coil arrangement and the secondary coil arrangement do not need to be electrically connected and can be spaced apart from each other.

[0003] It is possible for one or more of the coil assemblies to have one or more windings around a coil core. Typical coil core materials consist of or include ferrite. A certain amount of transmitted power is generally dissipated, i.e., converted into heat, in the coil core. Furthermore, a suboptimal alignment between the primary and secondary coil assemblies results in a variable coupling factor.

[0004] From the publication US 2018 / 0 331 578 A1, magnetic structures for inductive energy transmission are known in which several coil sections are wound around a core.

[0005] From the publication US 2009 / 0 072 628 A1, antennas for wireless energy transmission are known, which are particularly suitable for mobile devices.

[0006] From the publication WO 2015 / 087 138 A2 a power transmission system is known in which a configuration of transmitting coils can be adapted to different primary coils.

[0007] The document US 5 917 307 A describes a device for charging an electric vehicle via a magnetic coupling.

[0008] A system for wireless energy transmission via magnetic fields is known from the publication WO 2011 / 112 795 A1.

[0009] One way to reduce power dissipation is to increase the volume of the ferrite core. One way to reduce the variability of the coupling factor is to use coils with a generally low coupling factor, such as DD (double-D) coils or toroidal coils, whose windings are arranged essentially in a single plane.

[0010] However, an increased volume of the coil core leads to higher costs for such systems, as more ferrite material is required. Furthermore, the design size increases, which runs counter to the trend toward component miniaturization. Furthermore, an increased volume makes it more difficult to dissipate the heat generated by power loss.

[0011] On the other hand, the use of coils with low coupling factors leads to transmission systems with low magnetic coupling.

[0012] There is therefore a demand for coil assemblies with reduced losses and a relatively high but stable coupling factor. In particular, coil assemblies are in demand that require less ferrite in the coil core, yet can ensure good heat dissipation, have reduced mass, are easy to integrate into systems, can be provided at reduced cost, and can be operated with a stable and high coupling factor even with variable alignments between the primary and secondary coil assemblies.

[0013] For this purpose, a coil arrangement according to the independent claim is specified. Dependent claims specify advantageous embodiments.

[0014] The coil assembly has a coil core and a first winding. The turns of the first winding are wound around an axis. The turns of the first winding are distributed across several sections, and the sections of the first winding are spaced apart from each other.

[0015] Such spatial division of the winding turns of a coil arrangement leads to a distribution of the associated magnetic flux over a larger volume. The magnetic flux density is thus reduced. The power loss in the coil cores of coil arrangements is determined by the Steinmetz equation. The power loss is proportional to B m y , where B m is the magnetic flux density and y is a material constant of the coil core.

[0016] For a typical ferrite material, such as PC95, y is approximately 2.84. This means that the power dissipation is disproportionate to the magnetic flux density, and distributing a certain amount of magnetic flux over a larger volume leads to reduced power dissipation by reducing the maximum flux density.

[0017] Dividing the turns of the first winding into spaced-apart sections also reduces the corresponding coupling factors. The reduction is greater for high coupling factors than for lower coupling factors. The range of coupling factors—depending on the orientation relative to a primary coil arrangement of a WPT system—is thus reduced. At the same time, a coil type with a generally higher coupling factor, such as a solenoid coil, can be used.

[0018] Overall, a coil arrangement with low losses and lower fluctuation of the coupling factor while still maintaining a high coupling value is obtained.

[0019] Each section of the first winding can have a helical first winding with one or more layers.

[0020] It is possible that the coil consists essentially only of the spaced sections between which no further complete winding - but possibly electrical connections - are arranged.

[0021] The axis runs through the coil core.

[0022] The sections of the first winding protrude along the axis beyond opposite ends of the coil core.

[0023] Accordingly, it is also possible for the coil core to comprise or consist of a ferrite material. The ferrite material can be selected from the following materials: Ferrite N87 from TDK Corporation ®, Ferrite N95 from TDK Corporation ®, Ferrite N97 from TDK Corporation ®, Ferrite PC47 from TDK Corporation ®, Ferrite PC95 from TDK Corporation ®.

[0024] It is possible that the coil core is selected from an unclaimed cylindrical coil core, a claimed plate-shaped coil core, a plate-shaped coil core with a rectangle as a base area.

[0025] Plate-shaped coil cores with a rectangle as their base are essentially cuboids with a length, a width and a thickness.

[0026] The coil core has a rectangular base with a width b and a length l along the axis. The coil core also has a thickness d. The width can be 200 mm or more and 300 mm or less. The length can be 350 mm or more and 450 mm or less. The thickness can be 9 mm or more and 15 mm or less.

[0027] In particular, the width can be 250 mm, the length 400 mm and the thickness 12 mm.

[0028] The number of sections can be two, three, four, five or six or more.

[0029] In particular, it is possible that the number of sections is exactly two.

[0030] It is possible that two sections of the first winding are arranged on opposite sides of the coil core.

[0031] In particular, it is possible that two sections are arranged on opposite sides of the coil core and the two opposite sides with the greatest distance are sides of a cuboid coil core.

[0032] It is possible for the distance between sections of the first winding to be greater than 0 and less than 0.9 in units of the length l of the coil core. Alternatively or additionally, it is possible for the distance to be 0.2 or greater and 0.9 or less in units of l. Furthermore, it is possible for the distance to be 0.4 or greater and 0.9 or less in units of l. Furthermore, it is possible for the distance to be 0.6 or greater and 0.9 or less in units of l. Furthermore, it is possible for the distance to be 0.8 or greater and 0.9 or less in units of l.

[0033] A preferred distance in units of l is 0.6.

[0034] It is possible for a section to have a spatial extension in the direction of the winding axis of 0.15 or more and 0.25 or less in units of l. An extension in the direction of the winding axis can be 0.2 l.

[0035] It is possible for the coil arrangement to further comprise a thermal bridge. The thermal bridge can be arranged in the axial direction, i.e., in a direction along the first winding axis, between two sections of the first winding and on the coil core. In particular, it is possible for the thermal bridge to be provided and suitable for dissipating heat from the coil core to an external environment.

[0036] The external environment of the coil arrangement can be an atmosphere surrounding the coil arrangement, for example air.

[0037] Furthermore, it is possible for the coil assembly to be attached to a device. In this case, the thermal bridge can be designed and adapted to dissipate heat from the coil core to the device and to the atmosphere. The thermal bridge can comprise cooling fins.

[0038] The device to which the coil arrangement can be attached can be the receiver of the electrical energy that the coil arrangement receives in the form of magnetic energy. For example, a rechargeable energy storage device of a vehicle or other movable object can be charged.

[0039] The coil assembly includes a second winding having one or more sections.

[0040] It is possible that the second winding comprises two or more sections.

[0041] It is possible that the sections of the second winding are spaced apart from each other.

[0042] It is possible that the sections of the second winding are spaced from sections of the first winding.

[0043] The turns of the sections of the second winding are also wound around the axis of the first winding.

[0044] The coil core is also the core for the turns of the sections of the second winding.

[0045] The coil arrangement further comprises a switch.

[0046] The switch can be used to activate the sections of the first winding or the sections of the second winding.

[0047] Alternatively, the sections of the second winding can be connected between the sections of the first winding using the switch.

[0048] The presence of the second winding makes it possible to select the active sections depending on the orientation of the coil arrangement - as a secondary coil arrangement - to a primary coil arrangement, so that sections of the coil arrangement are active so that the coupling factor can be kept in an even narrower range.

[0049] This reduces the fluctuation range of the coupling, while still maintaining a relatively high coupling factor.

[0050] This reduces the stress on windings and matching networks in WPT systems. Thus, good transmission efficiency can be achieved with a simple and easy-to-control matching network.

[0051] Accordingly, it is possible that the coil arrangement is a secondary coil arrangement of a system for wirelessly transmitting electrical energy.

[0052] Accordingly, a system for wirelessly transmitting electrical energy may comprise a coil arrangement as described above as a secondary coil arrangement and additionally a primary coil arrangement.

[0053] It is possible for the primary coil arrangement to comprise a double-D coil arrangement, a solenoid coil, a spiral coil or a circular coil which has two coil sections which, in contrast to the secondary coil arrangement described above, are not wound coaxially, but whose two windings are arranged next to each other in the same plane.

[0054] Central aspects of the coil arrangement and details of preferred embodiments are explained in more detail using the schematic figures.

[0055] They show: Fig. 1 the relative arrangement of the coil core and the sections in a plan view, Fig. 2 the arrangement in cross section, Fig. 3 the use of a thermal bridge, Fig. 4 the dependence of the inductance and losses of a coil arrangement on the extension of a section in the axial direction, Fig. 5 The dependence of the fluctuation range of the coupling factor on the width of a winding section, Fig. 6 a coil arrangement with two windings in plan view, Fig. 7 a coil arrangement with two windings in cross section, Fig. 8 a possible connection of the sections of two windings, Fig. 9 another possible connection of the sections of two windings, Fig. 10 and Fig. 11 the variable orientation of the coil arrangement relative to a primary coil arrangement, Fig. 12 the resulting reduced fluctuation range of the magnetic coupling factor of a coil arrangement with two windings.

[0056] Fig. Figure 1 shows the arrangement of the two sections A1, A2 of a coil, whose first winding is divided into two sections, in relation to the associated coil core K in a top view. The coil core K has a rectangular base with a length in the axial direction x - l and a width in the lateral direction y - b. At the ends of the coil core K, which are the largest apart from each other, the two sections A1, A2 of the first winding are arranged. The sections have a distance d. Fig. 1 a form of coil arrangement with exactly two sections.

[0057] The two sections DDC1 and DDC2 of a primary coil assembly in a double-D configuration are shown in dashed lines. The coil sections DDC1 and DDC2 of the primary coil assembly, together with the two sections A1 and A2 and the coil core K of the coil assembly as a secondary coil assembly, form the magnetically active components of a system for wirelessly transmitting electrical energy (WPTS).

[0058] Dividing the first winding of the secondary coil arrangement into two spaced-apart sections results in a distribution of the magnetic flux over a larger volume, especially in the coil core K, so that the magnetic flux density in the coil core K is reduced. Due to the disproportionate dependence of transmission losses on the magnetic flux density, this results in a reduction of energy losses or power losses when transmitting electrical energy.

[0059] Fig. Figure 2 shows the arrangement of the components of the energy transmission system in cross-section. Each of the two sections A1, A2 of the first winding of the coil arrangement has conductor sections arranged above the material of the magnetic core K, as seen in the vertical direction (Z), and conductor sections arranged below the magnetic core K.

[0060] In the axial direction (x), the sections do not need to be flush with the magnetic core K. It is possible that, as claimed, the sections of the first winding protrude beyond the respective ends of the coil core (as in Fig. 2). However, it is also possible, in a non-claimed manner, for the coil core to be exactly flush with the sections at the respective ends.

[0061] It is also possible, in a manner not claimed, for the coil core K to protrude beyond the distal ends of the sections A1, A2.

[0062] The arrows essentially illustrate the course of the magnetic field lines at a specific point in time.

[0063] Fig. Figure 3 illustrates the possibility of using a thermal bridge WB to dissipate dissipated energy, which accumulates in the form of heat in the coil core K, to an external environment. The external environment may, in particular, be a mounting base B of a device to which the coil assembly delivers electrical energy.

[0064] Fig. Figure 4 shows the dependence of the inductance I and the power losses PL on the width b of a winding section of a secondary coil arrangement of a wireless energy transmission system. While the inductance remains essentially constant, the power loss decreases with decreasing width b. This means that dividing a first winding of a certain width into two spaced-apart sections, each with a smaller width, significantly reduces the power losses.

[0065] Fig. Figure 5 shows the dependence of the width of the coupling factor variation KFSB on the width bA (i.e., the extension in the x-direction) of a section of a winding. A reduction in the width is accompanied by a reduction in the change in the coupling with varying alignment between the primary and secondary coil arrangements.

[0066] The Fig. Figures 6 (top view) and 7 (cross-section) show a coil arrangement that, in addition to the first winding with sections A1 and A2, also includes sections A21 and A22 of a second winding. The ability to activate different sections of the windings via a switch allows the coupling factor range to be further narrowed, thus further stabilizing operation.

[0067] Fig. Figure 8 shows a possible connection of the winding sections when used on the receiver side of a WPT system. Using switch SW, either the first winding W1 with sections A1 and A2 or the second winding with sections A21 and A22 can be activated. The choice between the first and second windings can be made, for example, based on the spatial arrangement of the sections for arranging a primary coil.

[0068] A capacitive element CE can serve as a matching element or as part of a matching network. The four diodes in a rectifier configuration then provide a DC voltage.

[0069] Fig. Figure 9 shows a possible connection of the winding sections when used on the receiver side of a WPT system. Using switch SW, either only the first winding W1 with sections A1 and A2 is active. Or, sections A21, A22 of the second winding are connected in series between sections A1, A2 of the first winding. The choice of switch position can again be made based on the spatial arrangement of the sections for the arrangement of a primary coil.

[0070] A capacitive element CE can serve as a matching element or as part of a matching network. The four diodes in a rectifier configuration then provide a DC voltage.

[0071] The Fig. 10 and Fig. 11 shows possible orientations of the coil arrangement as a secondary coil arrangement of a WPT system relative to the DD coil with the coil sections DDC1, DDC2 of a primary coil arrangement of the WPT system. Sections A1 and A2 can be active when the height difference between the transmitter (primary coil) and the receiver (secondary coil) is relatively small. Furthermore, sections A21 and A22 can be active when the height difference is relatively large.

[0072] Alternatively, it is possible - with more switches - that the two sections A1 and A21 can be used together or that sections A22 and A2 can be used together, depending on the orientation to the transmitter.

[0073] This makes it possible to obtain a good coupling factor in a narrow range despite a multitude of different – and therefore variable – orientations of the secondary coil arrangement.

[0074] Fig.Figure 12 shows the possible coupling factors for the first winding (1) and the second winding (2) for different orientations of the coil arrangement. Thus, the coupling factor for the first winding can vary between 47% and 100%. The coupling factor for the second winding can vary between 61% and 136%. By switching sections, a switch position can be found for every possible orientation of the secondary coil arrangement, so that the coupling factor lies between 61% and 100%.

[0075] The coil arrangement is not limited to the technical features shown in the figures or described above. The coil arrangement can include additional windings with additional sections, switches, conductor sections, for example, for electrically connecting the sections, electrical connections for connecting to an external circuit environment, additional elements for guiding the magnetic flux, or mounting options for contacting. List of reference symbols A1, A2 first, second section of the first winding of the coil arrangement A21, A22 first, second section of the second winding b Width of the coil core bA Width of a section B Basis for dissipating heat energy CE capacitive element d Distance between the sections of the winding D Thickness of the coil core DDC1, DDC2 coil sections of a primary coil arrangement I Inductance K Coil core KFSB Fluctuation range of the coupling factor l Length of the coil core PL power loss W1, W2 first, second winding WB thermal bridge WPTS system for wireless transmission of energy x axial direction y transverse direction z vertical direction

Claims

[1] Coil arrangement with reduced losses and stabilized coupling factor, comprising - a coil core (K), - a first winding (W1), the turns of which are wound around an axis (x) passing through the coil core (K), - a second winding (W2) with one or more sections (A21, A22) whose turns are wound around the axis (x) of the first winding (W1), - a switch (SW), where - the coil core (K) has a rectangular base with a width b, a length l in the direction of the axis (x) and a thickness d, - the turns of the first winding (W1) are distributed over several sections (A1, A2), - the sections (A1, A2) are spaced apart from each other, - the coil core (K) is the core for the turns of the sections (A21, A22) of the second winding (W2), - the sections (A1, A2) of the first winding (W1) project along the axis (x) beyond opposite ends of the coil core (K), - using the switch (SW) either • the sections (A1, A2) of the first winding (W1) or the sections (A21, A22) of the second winding (W2) can be activated or • the sections (A21, A22) of the second winding (W2) can be connected between the sections (A1, A2) of the first winding (W1). [2] Coil arrangement according to the preceding claim, which consists only of the spaced sections (A1, A2) and electrical connections without a complete turn. [3] Coil arrangement according to one of the preceding claims, wherein the coil core (K) comprises or consists of a ferrite material. [4] Coil arrangement according to one of the preceding claims, wherein - the coil core (K) is plate-shaped, - the rectangular base area has a width b of 200 mm ≤ b ≤ 300 mm, a length l of 350 mm ≤ l ≤ 450 mm and a thickness d of 9 mm ≤ d ≤ 15 mm. [5] Coil arrangement according to one of the preceding claims, wherein the number of sections (A1, A2) is 2, 3, 4, 5, 6 or more. [6] Coil arrangement according to one of the preceding claims, wherein two sections (A1, A2) are arranged on opposite sides of the coil core (K). [7] Coil arrangement according to one of the preceding claims, wherein the distance d between sections (A1, A2) of the winding (W1) is: • 0 < d ≤ 0.9 l or • 0.2 l ≤ d ≤ 0.9 l or • 0.4 l ≤ d ≤ 0.9 l or • 0.6 l ≤ d ≤ 0.9 l or • 0.8 l ≤ d ≤ 0.9 l. [8] Coil arrangement according to one of the preceding claims, further comprising a thermal bridge (WB) which is arranged in the axial direction between two sections (A1, A2) of the winding (W1) and on the coil core (K) and is intended and suitable for dissipating heat to an external environment. [9] Coil arrangement according to one of the preceding claims, wherein the second winding (W2) comprises two or more sections (A1, A2). [10] Coil arrangement according to the preceding claim, wherein the sections (A21, A22) of the second winding (W2) are spaced apart from each other. [11] Coil arrangement according to one of the preceding claims, wherein the sections (A21, A22) of the second winding (W2) are spaced from sections (A1, A2) of the first winding (W1). [12] Coil arrangement according to one of the preceding claims, which is a secondary coil arrangement of a system for wirelessly transmitting electrical energy. [13] System for wirelessly transmitting electrical energy, comprising a coil arrangement according to one of the preceding claims as a secondary coil arrangement and a primary coil arrangement. [14] System according to the preceding claim, wherein the primary coil arrangement comprises a double-D coil, solenoid coil, spiral coil or circular coil.

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