Annular magnetic core assembly with isotropic magnetic bridge

Abstract

One embodiment relates to a toroidal core assembly. The annular belt magnetic core is formed by winding a ferromagnetic belt, and the magnetic conduction piece is arranged on the annular belt magnetic core. A magnetic conductor is disposed laterally on the endless belt core such that it (mechanically) is in contact with the narrow sides of the plurality of tape layers of the endless belt core.

Description

Field of the Invention

[0001] The invention relates to a ring-shaped magnetic core component which can be used, for example, in a current-compensated choke. Background Art

[0002] Toroidal core assemblies are desired for many applications and may have a strip made of ferromagnetic material in the central opening of the toroidal core. Such toroidal core assemblies are used in the construction of filter chokes such as Common-Mode Chokes (CMC) or Differential-Mode Chokes (DMC). Toroidal cores are not necessarily circular, but are typically elliptical. The term "toroidal core" does not imply any particular shape (such as circular or elliptical), but simply means that the core extends along a closed curve. Typically, toroidal cores are made of ferromagnetic tape wound around them, so they are also called toroidal strip cores.

[0003] Filter chokes having an annular core (eg CMC or DMC) in which a ferromagnetic strip is inserted in the central opening to guide the magnetic flux may show unsatisfactory performance in practice, ie the magnetic characteristics of the filter choke do not meet expectations.

[0004] The inventors aimed to improve the well-known design concept of toroidal core components, in particular for filter chokes. Summary of the invention

[0005] One embodiment relates to a toroidal core assembly, which includes an annular belt core formed by winding an iron magnetic tape and at least one magnetic guide, which is disposed transversely on the annular belt core so as to (mechanically) contact the narrow sides of multiple belt layers of the annular belt core.

[0006] Another embodiment relates to a filter choke having an annular tape core wound by an iron tape and having two coils wound on the annular tape core. The filter choke also has at least one magnetic guide disposed between the first coil and the second coil and disposed transversely on the annular tape core so that the magnetic guide contacts the narrow sides of the plurality of tape layers of the annular tape core. BRIEF DESCRIPTION OF THE DRAWINGS

[0007] Various embodiments are explained in more detail below using the accompanying drawings. The drawings are not necessarily to scale, and the present invention is not limited to the aspects shown in the drawings. Instead, the emphasis is on explaining the basic principles of the illustrated embodiments.

[0008] Figure 1 A toroidal core assembly is shown in (a) a top view and (b) a perspective view, the toroidal core assembly having an elliptical toroidal core with a strip made of ferromagnetic material inserted into its central opening.

[0009] Figure 2 Shown in Figure 1 Magnetic saturation effects that may occur in the toroidal core assembly.

[0010] Figure 3 A section of an iron tape is shown, Figure 1 The toroidal core in the circuit is wound with it.

[0011] Figure 4 A toroidal magnetic core assembly is shown, comprising Figure 3 An annular belt magnetic core formed by winding an iron magnetic tape and a magnetic guide piece installed laterally on the annular belt magnetic core.

[0012] Figure 5 Shows something like Figure 4 The invention is a toroidal magnetic core assembly, but has two magnetic guide members symmetrically arranged on the toroidal magnetic core.

[0013] As another example, Figure 6 Shows Figure 5 and Figure 1 A combination of examples.

[0014] Figure 7 Shows Figure 4 alternative.

[0015] Figure 8 Another embodiment is shown in which the flux guide is mounted transversely to the annular core and passes through the central opening of the core.

[0016] Fig. 9 Shows Figure 8 Several variations / alternatives to the example.

[0017] Fig.10 The application of the toroidal core assembly described in this article in the design of a filter choke is shown.

[0018] Fig.11 An example of a toroidal core assembly for a multi-phase system is shown. DETAILED DESCRIPTION

[0019] Figure 1By way of example, a toroidal core assembly having an elliptical toroidal core 101 is shown, in whose central opening 102 (defined by the toroidal core 101) a strip made of ferromagnetic material is inserted. The toroidal core has (at least) two axes of symmetry A and B. In the example of an elliptical core shown, the elliptical profile of the core has exactly two axes of symmetry. The strip is also referred to as a flux guide. As mentioned above, the term "elliptical" generally refers to a circle, but not necessarily an ellipse. In this case, a rectangle or square with rounded corners can also represent an ellipse. A circle is a special case of the general term "ellipse". Typically, an ellipse has at least two axes of symmetry that intersect at a center point.

[0020] In the example shown, the magnetic guide consists of two strip elements 110 and 120. These strip elements are prism-shaped with a triangular base. In other words, the strip elements 110, 120 have a wedge shape that slides against each other. In the assembled state, the strip elements 110, 120 form an approximate rectangular parallelepiped shape. By means of the wedge shape of the strip elements 110, 120, a very small air gap can be achieved between the strip elements 110, 120 and the inner wall 103 of the annular core 101 and manufacturing tolerances are balanced. The remaining (and unavoidable) air gap is determined by any coating of the magnetic tape material of which the annular core is manufactured and its surface roughness. Typically, an air gap of less than 10 μm can be achieved.

[0021] As mentioned previously, it has been found in practice that the actual magnetic properties of the core and hence the properties of the filter choke are worse than would be expected from the usual design rules. Figure 2 The reasons that may cause the characteristics of the filter choke to deteriorate are explained. It should be understood that Figure 2 Just a simplified, not-to-scale schematic. Figure 2 The toroidal core 101 shown has four layers stacked on top of each other. As mentioned above, the illustration is very simplified (but sufficient to explain the problem). In reality, a toroidal core has hundreds of layers, which are made of iron tape wound around it. Figure 2 The conductors L1 and L2 shown in are busbars passing through the toroidal core. The direction of current flow is indicated by the dots (·) and crosses (×). This means that Figure 2 In the figure, a cross section of the conductors can be seen, with the current flowing perpendicular to the drawing plane. Dots represent current flowing out of the drawing plane, and crosses represent current flowing into the drawing plane. Conductors L1 and L2 can also be interpreted as single-turn windings. In some embodiments, windings with multiple turns can also be used (see also Fig.10 ).

[0022] The thickness of the magnetic tape from which the toroidal core 101 is made may be in the range of 10-1000 μm (typically 20 μm for example). The magnetic tape may also have a coating of, for example, aluminum oxide, zirconium oxide, magnesium oxide and / or silicon oxide. For example, a material that may come into consideration is a nanocrystalline iron alloy, which may contain, for example, parts of silicon, niobium, boron and copper. A specific example of a suitable alloy is Depending on requirements (ie depending on the desired application), the relative magnetic permeability μr of the magnetic tape material can be adjusted to a specific μr value between 100 and 1,000,000 by varying the alloy composition and annealing.

[0023] Especially for alloys with a relatively high silicon content (e.g. 5-10 weight percent), the formation of a silicon oxide layer on the surface is practically unavoidable. Due to the aforementioned coating (e.g. SiO2) and the inevitable surface roughness, when the magnetic tape is wound into a toroidal core, gaps of several micrometers (e.g. 2-10 μm) remain between the layers. Even though these gaps contain not only air, they are also called "air gaps" because they have magnetic properties like air gaps.

[0024] The tape has a top, a bottom, and two (narrow, only a few microns wide) sides. During the winding process, the top of one layer is adjacent to the bottom of the layer above. Due to the reasons mentioned above, an air gap of a few microns is left between the top and bottom of two adjacent layers ( Figure 2 In Figure 2 In the simplified model of , the air gap is located between the layers 101a-d of the toroidal core.

[0025] Surprisingly, research has shown that in practice, when the current is relatively high (through the coils L1, L2 wound on the core (or the coils wound on the strips 110, 120), causing the magnetic flux to be generated in the strips 110, 120), the toroidal core is not uniformly saturated, but magnetic saturation first occurs in the innermost layer (or a few inner layers). Figure 2 In the figure, the magnetic saturation of the innermost magnetic tape layer is indicated by gray shading.

[0026] Due to the mentioned micro air gaps between the individual tape layers, the toroidal tape core acquires magnetic anisotropy. Within one tape layer, the relative magnetic permeability is very high, and therefore the magnetic resistance is very small. Between two adjacent tape layers, the micro air gaps form a significant magnetic resistance, resulting in the magnetic field lines tending to stay within one tape layer. This results in the magnetic flux being concentrated on the inner tape layer, while the magnetic flux density decreases outwards, i.e. in the tape layers further out of the toroidal tape core.

[0027] The magnetic saturation of the inner tape layers has an effect on the magnetic permeability 110 / 120 located in the central opening of the toroidal core 101 and connected (mechanically and magnetically) to the opposite (lower) side of the innermost tape layer 101a. If the innermost tape layer 101a is magnetically saturated, its (differential) relative permeability (Partial derivative of magnetic flux density B with respect to magnetic field strength H divided by vacuum permeability μ0) theoretically drops significantly to 1, which is why the magnetically saturated tape layer 101a behaves as an air gap magnetically. This means that magnetic saturation creates an "air gap" between the two ends of the magnetic permeable member 110 / 120 and the annular tape core 101, the gap width of which is at least the same as the thickness of the tape layer. If the innermost ten tape layers are saturated, the width of the air gap created by the saturation of the inner tape layers will be, for example, ten times the thickness of the tape layer.

[0028] The increased effective air gap width due to the magnetic saturation of the innermost magnetic layer can lead to a degradation of the DMC performance of filter chokes with such a toroidal core assembly. In particular, the magnetic saturation has a negative impact on the performance of the filter choke (especially the inductance). If high-frequency interference currents are superimposed on the direct current (flowing through conductors L1 and L2, see Figure 2 ), the resulting magnetic flux is approximately perpendicular to the plane of the tape, resulting in high parasitic eddy currents in the tape layers within the tape plane. The embodiments described below (see Figure 4-6 ) aims to improve this situation, that is, to improve the magnetic properties of the toroidal core assembly (and the filter choke constructed therefrom).

[0029] Figure 3 The diagram shows a short section of an iron magnetic tape that can be used to make an annular tape core 101. As previously mentioned, the thickness of the tape is about 10 μm. The tape has a top and a bottom (top and bottom major surfaces). The height of the narrow side corresponds to the thickness of the tape. When the tape is wound into an annular core, the bottom of one winding rests on the top of the winding below. As previously mentioned, this results in an unavoidable (gap) gap that causes the annular tape core 101 to have a lower magnetic resistance in the plane E of the tape than in the normal direction of the tape plane E. Figure 3 In FIG. , the “high magnetoresistance direction” is indicated by an arrow.

[0030] Figure 4 A first embodiment is shown, wherein FIG. (a) is a top view and FIG. (b) is a side view. Figure 2 Similarly, the various magnetic tape layers 101a-d shown in the figure are only symbolic. In reality, the annular magnetic core is wound with hundreds of windings of iron magnetic tape. Figure 1 The difference is that the magnetic guide / strip 130 is not inserted into the central opening of the annular core 101, but contacts the side of the magnetic tape layers (especially all the magnetic tape layers) of the annular core 101 (in particular, the magnetic tape layers). Figure 3That is, the strip 130 touches the side of the toroidal core and is not necessarily located within the central opening. For this reason, the strip / flux guide may also be referred to as a "bridge". The strip 130 may be arranged along one of the symmetry axes A or B (in the example shown, along the symmetry axis A). The strip / flux guide 130 may be made of a material having a specified relative permeability μ r The material may be an isotropic ferromagnetic material such as ferrites, iron powder (nickel-iron or cobalt-iron powder) bonded (eg by phosphates) or a metal powder alloy consisting of a crystalline, amorphous or nanocrystalline alloy (eg nickel-iron or cobalt-iron).

[0031] The flux guide / strip 130 may be in the form of a sheet with a rectangular profile. This means that geometrically the sheet is an elongated cuboid with a very narrow base and cross section. The strip 130 may be fixed to the annular tape core by force-locking, for example, with the aid of a plastic casing (not shown) surrounding the annular core and the strip 130. Other methods of mounting the strip 130 to the annular core 101 are also possible. Since the strip / flux guide contacts the narrow sides of the tape layers 101a-d, the magnetic resistance between the annular tape core 101 and the flux guide 130 is reduced, in particular, the saturation of the innermost tape layer 101a does not lead to an increase in the air gap between the annular tape core 101 and the flux guide. The magnetic flux (magnetic lines of force) may extend to the flux guide 130 in the tape plane E. As previously mentioned, the magnetic resistance in the tape plane E is lower than the magnetic resistance perpendicular to the tape plane, and when an alternating current (AC) field penetrates, significant and significantly low eddy currents are generated. The annular ribbon core 101 and the strip 130 may be electrically isolated from each other.

[0032] Figure 5 Another embodiment is shown, in which the magnetic guide member 130 is divided into two. That is, the strip 130a is located on one side of the annular core 101 and contacts the narrow side of the magnetic tape layer (such as Figure 4 ), while the other strip 130b is located on the opposite side of the annular tape core 101 (and in contact with the opposite narrow side of the magnetic tape layer). Figure 5 The symmetrical design of the core assembly shown further enhances its magnetic performance.

[0033] Figure 6 The example in can be seen as Figure 5 and Figure 1 Although the magnetic guide (composed of elements 110 and 120) in the central opening is not absolutely necessary, when combined with Figure 4 The magnetic guide member 130 or Figure 5 When the magnetic guides 130a and 130b are combined, they can bring benefits in the magnetic properties of the core assembly in certain applications.

[0034] As another example, Figure 7 The diagram shows Figure 4A modification of the example by Figure 7 It can be seen that the strip 130 does not have a rectangular cross-section (e.g. Figure 4 101 ) but a trapezoidal cross section, wherein the larger side of the strip 130 contacts the end face of the annular core to further enhance the guidance of the magnetic flux. In addition, an electrical insulating sheet may be provided between the magnetic guide 130 and the annular core, so that the magnetically effective (gap) gap between the annular core 101 and the magnetic guide 130 is determined by the thickness of the sheet. This option applies to all examples described herein.

[0035] Figure 8 Another embodiment is shown in which the magnetic guide 130 is transversely mounted on the annular tape core 101 (e.g., by adhesive), but passes through the central opening of the core. That is, both ends of the magnetic guide 130 are connected to opposite end surfaces of the annular tape core. As in the previous example, the end of the magnetic guide 130 contacts multiple magnetic tape layers on one side of its narrow side. Figure 8 Figure (a) is a top view (similar to Figure 4 Figure (a)), Figure 8 Figure (b) is a cross-sectional view, in which the cutting plane extends along the symmetry axis A and is perpendicular to the symmetry axis B.

[0036] Fig. 9 Shows the Figure 8 Some modifications and variations of the examples. Fig. 9 All examples in the Figure 8 (b) is a cross-sectional view of the Fig. 9 In all the examples shown, two flux guides 130a and 130b are combined. Fig. 9 In the example of FIG. (a), two magnetic guides obliquely pass through the central opening of the annular core 101, wherein both ends of the two magnetic guides 130a and 130b are connected to opposite end surfaces of the annular core. The variant shown in FIG. (b) is similar to Figure 6 , wherein element 130a has a wedge-shaped portion that extends into the central opening of the ring-shaped core 101. In both figures (a) and (b), elements 130a and 130b are identical, wherein element 130b is rotated 180° (relative to element 130a) and inserted into the ring-shaped core 101 from the other side.

[0037] Fig. 9 The variants shown in Figures (c) and (d) are identical in the assembled state. In both cases, the strips 130a and 130b form a magnetic guide that is separated in the horizontal direction in Figure (c) and in the vertical direction in Figure (d). In another example, the elements 130a and 130b are formed as one piece.

[0038] Fig. 9The variation shown in FIG. (e) shows an annular core including a first annular core 101, a second annular core 102 and a strip 130 disposed therebetween. The strip 130 may be arranged in a manner similar to Figure 4 The strip is mounted on the toroidal core 101 in an exemplary manner (e.g., by adhesive). On the other side of the strip, a second toroidal core 102 is fixed in the same manner. For example, the toroidal core stack including the strips can be arranged in a plastic housing. Other configurations of strips / magnetic guides shown here can also be used with the toroidal core stack.

[0039] Fig.10 The application of a magnetic core assembly (annular magnetic core 101 plus a magnetic permeable member 130) in a filter choke is schematically illustrated. Figures (a) and (b) relate to common mode chokes (CMC), and Figures (c) and (d) relate to differential mode chokes (DMC). The working principle of this type of filter choke is known and will not be explained in detail. The arrows in Figures (a) and (c) represent the interference current (and its direction) passing through the coil, and the arrows in Figures (b) and (d) represent the corresponding directions of the generated magnetic flux in the magnetic core assembly. Figure 6 It can also be seen that the annular core is not necessarily elliptical, but can also be circular (or have other different shapes).

[0040] Fig.11 The top view (Fig. (a)) and the side view (Fig. (b)) of the ring core assembly of a three-phase filter choke are shown. This concept can also be extended to more than three phases. In the example shown, the ring core is not elliptical, but has a circular contour, that is, the two opposite end faces of the ring core have the shape of a ring. Fig.11 , the magnetic guide 130 has three legs connected in the center of the ring. The three legs can be offset by 120°. In the example shown, the magnetic guide 130 is integral. The outer ends of the three legs contact the narrow edges of the various tape layers. The magnetic guide divides the annular tape core into three sections, and the annular tape core 101 in each of these sections can be wound with one or more coils. Figure 3-9 The variants shown can also be applied to magnetic core components of multiphase systems.

[0041] As mentioned above, the magnetic guides 130, 130a, 130b can be fixed to the ring-shaped core in a force-locking manner by means of, for example, a plastic housing surrounding the ring-shaped core and (multiple) magnetic guides. Alternatively, the magnetic guides can be firmly connected to one or both end faces of the ring-shaped core, for example, by means of an adhesive. The adhesive itself can be magnetic, for example, it can contain ferromagnetic particles (for example made of iron or ferrite). This further reduces the effective (magnetically effective) air gap between the magnetic guides and the narrow side of the ring-shaped core (see, for example Figure 3 ), the narrow side of the toroidal core is not completely flat due to winding offset.

[0042] Before the magnetic guide is laid on the magnetic core, adhesive can be applied to the narrow edges of the iron magnetic tape, so that any flaking pieces of magnetic tape material are caught by the adhesive.

Claims

1. A toroidal magnetic core assembly, characterized in that: include: An annular magnetic core (101) formed by winding an iron magnetic tape; At least one magnetic guide (130, 130a) is laterally arranged on the annular magnetic core (101) so as to contact the narrow sides of the plurality of magnetic tape layers (101a-d) of the annular magnetic core.

2. The annular magnetic core assembly according to claim 1, characterized in that: The annular magnetic core (101) has an elliptical profile with two symmetry axes (A, B).

3. The annular magnetic core assembly according to claim 2, characterized in that: The magnetic guide (130, 130a) is arranged along one of the symmetry axes (A, B) and is electrically isolated from the annular magnetic core.

4. The annular magnetic core assembly according to any one of claims 1 to 3, characterized in that: The magnetic guide member (130, 130a) is fixed on the annular magnetic core by adhesive.

5. The annular magnetic core assembly according to any one of claims 1 to 4, characterized in that: The magnetic guide member (130, 130a) has a sheet shape with an approximately rectangular outline.

6. The annular magnetic core assembly according to any one of claims 1 to 5, characterized in that: The annular magnetic core assembly comprises another magnetic guide member (130b), and the two magnetic guide members (130a, 130b) are located on opposite sides of the annular magnetic core.

7. The annular magnetic core assembly according to any one of claims 1 to 6, characterized in that: The magnetic guide member (130, 130a) is made of ferromagnetic and magnetically isotropic material.

8. The annular magnetic core assembly according to any one of claims 1 to 7, characterized in that: The ferrous tape has a non-magnetic layer on the top and / or bottom so that the annular tape core (101) has gaps between the layers of wound tape where the non-magnetic layer is located.

9. The annular magnetic core assembly according to claim 8, characterized in that: The non-magnetic layer is composed of ceramic materials such as silicon oxide, manganese oxide, zirconium oxide, aluminum oxide, or a combination thereof.

10. The annular magnetic core assembly according to any one of claims 1 to 9, characterized in that: The iron magnetic tape is composed of an iron alloy having a silicon content exceeding 5 weight percent.

11. The annular magnetic core assembly according to any one of claims 1 to 10, characterized in that: The magnetic guide (130, 130a, 130b) at least partially extends into the central opening of the annular magnetic core.

12. The annular magnetic core assembly according to any one of claims 1 to 10, characterized in that: The magnetic guide member (130, 130a, 130b) passes through the central opening of the annular magnetic core. The first end of the magnetic guide member (130, 130a, 130b) contacts the narrow sides of a plurality of tape layers (101a-d) on the first end side of the annular tape core (101), and The second end of the magnetic guide member (130, 130a, 130b) contacts the narrow sides of a plurality of tape layers (101a-d) on the second end side of the annular tape core (101).

13. The annular magnetic core assembly according to any one of claims 1 to 10, characterized in that: The magnetic guide has two elements (130a, 130b) which are located on opposite sides of the annular magnetic core (101) and at least partially extend into the central opening of the annular magnetic core (101) and contact each other in the central opening.

14. The annular magnetic core assembly according to any one of claims 1 to 13, characterized in that: Also includes: Another annular belt magnetic core (102), the magnetic guide member (130) is arranged between the annular belt magnetic core (101) and the another annular belt magnetic core (102) to contact the narrow sides of the multiple belt layers (101a-d) of the annular belt magnetic core (101) and the another annular belt magnetic core (102).

15. A filter choke, characterized in that: include: An annular magnetic core (101) formed by winding an iron magnetic tape; A first coil (L1) and a second coil (L2) wound on the annular magnetic core (101), and at least one magnetic guide (130, 130a), which is arranged between the first coil and the second coil (L1, L2) and laterally arranged on the annular magnetic core (101), so that the magnetic guide (130, 130a) contacts the narrow sides of multiple tape layers (101a-d) of the annular magnetic core.

16. The filter choke according to claim 15, characterized in that Also includes: The third coil, the magnetic guide (130) is arranged between the first coil and the second coil, the first coil and the third coil, and the second coil and the third coil.

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