Suppressor choke core, suppressor choke including such suppressor choke core, and method of forming suppressor choke core

Abstract

The present invention provides in various aspects a suppressor choke core, a suppressor choke including such a suppressor choke core, and a method of providing a suppressor choke core. In one aspect of the invention, the suppressor choke core comprises at least two hollow cylindrical core elements (3a, 3b), one of the hollow cylindrical core elements (3b) being disposed at least partially within the other of the hollow cylindrical core elements (3a) in series, and the hollow cylindrical core elements (3a, 3b) are permanently connected to each other to form a ferrite pipe core (3).

Description

[Technical field]

[0001] The present invention relates to suppressor choke cores, suppressor chokes including such suppressor choke cores, and methods of forming suppressor choke cores. [Background technology]

[0002] Chokes are generally used in electrical engineering as coils or inductors to limit the current in electrical lines, temporarily store energy in the form of a magnetic field, adjust the impedance of a circuit to a desired extent, and as filters. Unlike inductors in transformers and resonant circuits, chokes are usually connected in series with other components or consumers.

[0003] The magnetic core of a choke is usually made of a soft magnetic material, which increases the inductive resistance of the choke and allows the size of the choke to be reduced. A soft magnetic material is usually understood to be a material that can be easily magnetized in a magnetic field, such as ceramic materials in the form of ferrites based on metal oxides, such as manganese zinc ferrite and nickel zinc ferrite.

[0004] Suppressor chokes are a type of choke used to reduce high-frequency interference signals due to the high inductive resistance of the choke, while direct and low-frequency currents are not or only slightly affected. In a particularly simple form, suppressor chokes are formed by a toroidal core pressed into the cable or are provided by so-called split ferrites. For interference suppression in data bus systems, there are also different variations of high-frequency coils for interference suppression in the form of perforated, cylindrical or flat ferrite cores, which can be split as split ferrites. These ferrite cores are either clipped or screwed onto the current-carrying conductor or the ferrite cores are wound around the current-carrying conductor. However, cores clipped onto busbars and chokes with several windings are also known.

[0005] In the above mentioned applications, it is desirable to maintain the desired performance (i.e., filter effect and impedance) over a wide frequency range. However, the wideband performance is limited by eddy currents. Even if one attempts to reduce the eddy current losses of the solid core by means of minimizing the ratio of the flow area of ​​the ferrite core to the circumference, the wideband performance is still limited in such cases. In particular, this represents an approach in which, instead of a solid ferrite tube core, a ferrite tube core configured as a laminated core is formed from multiple tube core sections arranged one behind the other along the longitudinal direction of the ferrite tube core (corresponding to the azimuthal and radial directions given in the cylindrical coordinates of the ferrite tube core). As will be explained below with reference to FIG. 5, this approach is not a practical solution since the reduction of eddy current losses also limits the wideband performance.

[0006] Additionally, laminated cores formed as sintered cores require grinding and gluing of individual tube core sections to maintain conformal adhesion. These processing steps complicate the manufacturing process and increase the manufacturing costs of the corresponding cores.

[0007] Therefore, an object of the present invention is to provide a ferrite tube core as a suppressor choke core that has the desired wideband performance and can be easily manufactured.Another object of the present invention is to provide a suppressor choke core that has the desired wideband performance and can be easily manufactured.A further object of the present invention is to provide a method for forming a ferrite tube core as a suppressor choke core, which can easily manufacture a ferrite tube core with excellent wideband performance. Summary of the Invention

[0008] The above problem is solved in various aspects by a suppressor choke core according to independent claim 1, a suppressor choke according to independent claim 7 and a method according to independent claim 9. Preferred configurations of the suppressor choke core are defined in dependent claims 2 to 6, preferred configurations of the suppressor choke according to independent claim 7 are defined in dependent claim 8 and preferred configurations of the method according to independent claim 9 are defined in dependent claims 10 to 15.

[0009] In a first aspect of the present invention, a suppressor choke core is provided. In an exemplary embodiment of the first aspect, the suppressor choke core comprises at least two hollow cylindrical core elements, one of the hollow cylindrical core elements disposed at least partially contiguously within another of the hollow cylindrical core elements, and the hollow cylindrical core elements are permanently connected to each other to form a ferrite tube core. The ferrite tube core can be formed from a high magnetic permeability material, for example, the hollow cylindrical core elements can have a magnetic permeability μ of at least 2000, for example a relative magnetic permeability μ of at least 2000. r can exceed 2000. This provides a ferrite tube core with favorable broadband performance and easy manufacturing. The ferrite tube core can provide favorable filtering efficiency and impedance over a wide frequency range in a filter, and eddy currents are advantageously suppressed. In a specific embodiment, one of the hollow cylindrical core elements is completely surrounded by the other hollow cylindrical core element. When the hollow cylindrical core elements are each provided as a hollow cylinder, they can be arranged concentrically in succession with each other. In an embodiment herein, the ferrite tube core can have exactly two hollow cylindrical core elements.

[0010] The suppressor choke core according to the first aspect provides the possibility of suppression by providing the largest possible wideband reactance of the inductance with this ferrite tube core. Here, the inventors have realized that it is possible to limit the eddy current losses of the ferrite core without limiting the wideband performance of the inductance with this ferrite tube core. According to the principle of eddy currents, to reduce losses, the ratio of the area through which the current flows to the circumference of the ferrite core should be as low as possible. However, a small area rectangle with a large aspect ratio is more suitable than a circular area. This is achieved by splitting the ferrite core and inserting them into each other like sleeves to create an onion structure. In a specific embodiment, according to the first aspect, the cores inserted into each other to form an onion structure can be sintered together into a ferrite tube core, resulting in a high resistance form-fit connection.

[0011] An advantage of the suppressor choke core according to the first aspect is that the desired broadband performance can be achieved by only slightly subdividing the core, which allows for a relatively simple manufacturing process, since additional processing steps, such as additional grinding and gluing steps after sintering of the core layers, can be omitted, as compared to known cores having a laminated structure, for example, which reduces the manufacturing costs of the ferrite tube core according to the first aspect.

[0012] In some exemplary embodiments of the first aspect, at least two hollow cylindrical core elements may be sintered and / or bonded to form a separation layer between the core elements corresponding to the dispersion region and / or a bonded joint between the core elements, the separation layer or joint providing magnetoresistance between the core elements and improving wideband performance.

[0013] In some exemplary embodiments of the first aspect, the core elements can be made of the same material. This provides the advantage that the magnetic properties of the ferrite tube core can be obtained with a small tolerance since the hollow cylindrical core elements are made with a small tolerance. This is due to the fact that the shrinkage of the core elements when manufactured using the same material can be ignored since the core elements exhibit similar shrinkage. Alternatively, the core elements can be made of different materials, so that the magnetic properties of the ferrite tube core can be adapted using core elements made of different materials.

[0014] In some exemplary embodiments of the first aspect, the ferrite tube core can be configured to have an impedance of 580 Ω / m or more, preferably 600 Ω / m or more, and more preferably 700 Ω / m or more in the range of 10 kHz to 100 MHz. This represents a preferred impedance for high frequencies in the range of 10 kHz to 100 MHz. That is, a ferrite tube core with a small number of hollow cylindrical core elements, for example just two hollow cylindrical core elements, can achieve a specific impedance over a wide frequency range.

[0015] In some exemplary embodiments of the first aspect, the ferrite tube core can be configured to have an impedance of greater than 390 Ω / m, preferably greater than 400 Ω / m, in the range of 5 kHz to 100 MHz, which is a preferred impedance for high frequencies in the range of 5 kHz to 100 MHz.

[0016] In a second aspect of the present invention, there is provided a suppressor choke for suppressing high frequency interference. In an exemplary embodiment of the second aspect, the suppressor choke comprises a suppressor choke core according to the first aspect and at least one current conductor passing through the ferrite tube core, thereby providing a suppressor choke having favorable broadband performance and which can be manufactured in a simple manner.

[0017] In an exemplary embodiment of the second aspect, the at least one current conductor may include a bus bar passing through the ferrite tube core, making the suppressor choke suitable for use in high frequency applications of bus bar systems.

[0018] In a third aspect of the present invention, a method of forming a suppressor choke core is provided. In an exemplary embodiment of the third aspect, the method includes forming at least two hollow cylindrical core elements such that one of the hollow cylindrical core elements can be disposed consecutively within another of the hollow cylindrical core elements. In this process, at least two hollow cylindrical core elements are formed, and the formed hollow cylindrical core elements are configured to be disposed consecutively with one another. The method further includes arranging the at least two hollow cylindrical core elements in an arrangement in which one of the hollow cylindrical core elements is disposed consecutively within the other of the hollow cylindrical core elements, and permanently fixing the at least two hollow cylindrical core elements in the arrangement, thereby forming a suppressor choke core. The method allows for a simple manufacture of a suppressor choke core with favorable broadband performance. In a specific embodiment, the hollow cylindrical core elements can be disposed consecutively in a concentric manner. In the illustrative examples herein, the manufactured ferrite tube core is formed of a high magnetic permeability material, e.g., the hollow cylindrical core element has a magnetic permeability μ of at least 2000, i.e., a relative magnetic permeability μ r >2000. A properly manufactured ferrite tube core can provide a filter with favorable filtering effectiveness and impedance over a wide frequency range, and eddy currents are preferably suppressed.

[0019] In an exemplary embodiment of the third aspect, the ferrite tube core can have exactly two hollow cylindrical core elements. This means that, for example, a ferrite tube core with exactly two hollow cylindrical core elements or even a small number of hollow cylindrical core elements can achieve a specific impedance over a wide frequency range. For example, a ferrite tube core manufactured according to the third aspect can have an impedance of 580 Ω / m or more, preferably 600 Ω / m or more, more preferably 700 Ω / m or more, in the range of 10 kHz to 100 MHz. This represents a preferred impedance for high frequencies in the range of 10 kHz to 100 MHz. Furthermore, the ferrite tube core can have an impedance of more than 390 Ω / m, preferably more than 400 Ω / m, in the range of 5 kHz to 100 MHz. This is a preferred impedance for high frequencies in the range of 5 kHz to 100 MHz.

[0020] In some exemplary embodiments herein, forming the at least two hollow cylindrical core elements may include providing the at least two hollow cylindrical core elements as compressed green bodies, and the permanent fixing may include sintering the green bodies. As a result, a ferrite tube core can be formed in a simple manner based on the green bodies as pressed parts by sintering, the core elements are bonded to each other by sintering, and the ferrite tube core can be manufactured as a compact in a simple manner in only a few steps. In this case, a separation layer is provided by the dispersion boundaries between the sintered core elements.

[0021] In some alternative exemplary embodiments of the third aspect, the step of forming the at least two hollow cylindrical core elements may include providing the at least two hollow cylindrical core elements as compacted green bodies and then sintering the green bodies, and the step of permanently fixing may include gluing the at least two hollow cylindrical core elements or continuous pressing of the green bodies. In this case, the core elements may each be provided as a sintered ferrite core element in the form of a compact core element and then connected to each other in a gluing process by means of an adhesive joint. This allows a desired separation layer to be set through the adhesive joint. The thickness of the separation layer depends on the resistivity of the material of the separation layer (e.g., air, epoxy resin / glue, metal oxide) and the barrier layer resistance and can be appropriately selected. For example, in an exemplary example, the separation layer has a resistivity of at least 1×10 6 Ω or at least 1×10 2 The barrier layer resistance can be Ωm. For example, the thickness of the separation layer can be 5% or less of the radial thickness of the ferrite core element. Alternatively, during the successive pressing of the green bodies, a first green body can be formed from a first material, the first green body embedded in a second material, and the green body embedded in the second material can be pressed to form a successively wrapped green body.

[0022] In some exemplary configurations of these alternative exemplary embodiments of the third aspect, the method may further include finishing the at least two hollow cylindrical core elements after sintering by milling the at least two hollow cylindrical core elements into a desired shape, whereby milling can provide very low tolerances on the geometric dimensions of the core elements.

[0023] In some exemplary embodiments of the third aspect, the at least two hollow cylindrical core elements may be made of different materials, and the method may further comprise performing sintering according to a predetermined shrinkage of the batch of hollow cylindrical core elements and / or adjusting the resting time and cooling time during sintering to reduce distortion. This allows the geometric tolerance of the core elements to be minimized during manufacturing. This is because, on the one hand, the shrinkage occurring during sintering of dissimilar materials can be determined in advance and taken into account during the sintering process, and the sintering parameters (such as temperature, oxygen content, duration of the sintering process) can be pre-checked with respect to the shrinkage caused by them. Thus, optimal sintering parameters for the sintering process can be identified in advance and shrinkage can be minimized. Additionally or alternatively, distortion caused by temperature and cooling time can be avoided by adjusting the temperature and cooling time during sintering with the aim of preventing or minimizing distortion occurring during sintering.

[0024] In other exemplary embodiments and alternatives to the immediately preceding embodiment, the at least two hollow cylindrical core elements may be formed from the same material, and the method may further include adjusting the standing time and cooling time during sintering to reduce distortion.

[0025] In some exemplary embodiments, the method according to the third aspect may be used to manufacture a suppressor choke core according to the first aspect. Thus, in at least one exemplary embodiment of the third aspect, in a particular example, the method according to the third aspect is carried out to manufacture a suppressor choke core according to one of the exemplary embodiments of the first aspect. Furthermore, in an exemplary application of the method according to the third aspect, a suppressor choke according to the second aspect may also be manufactured accordingly, and further, after manufacturing the suppressor choke core, at least one current conductor is passed through the ferrite tube core or the ferrite tube core is clipped to at least one current conductor.

[0026] In the first to third aspects described above, in at least some exemplary embodiments of at least one of the first to third aspects described above, a suppressor choke core can be provided that can have high magnetic permeability and / or a substantially constant high magnetic permeability. For example, a magnetic permeability of more than 6000 can be achieved in a frequency range up to 20 kHz, for example, μ r can exceed 6000. For example, the high permeability in this frequency range can be basically maintained in the high permeability region of the ferrite tube core. Basically, the permeability of the ferrite tube core is basically constant in the range from 1 kHz to 20 kHz, so the permeability in the frequency range up to 10 kHz can exceed 9000, for example, μ r can exceed 9000. Thus, the suppressor choke provided according to the second aspect can exhibit a corresponding permeability shift in this frequency range. Furthermore, the permeability in the frequency range up to 50 kHz can be greater than 2000, preferably greater than 3000, more preferably greater than 4000, e.g. r >2000, preferably μ r >3000, more preferably μ r >4000.

[0027] Further advantageous effects and features of the present invention, as set forth above in its various aspects, will become apparent from the following detailed description of the accompanying drawings. [Brief description of the drawings]

[0028] [Figure 1] FIG. 1 shows a schematic perspective view of a known ferrite tube core. [Diagram 2] FIG. 2 shows a schematic perspective view of another known ferrite tube core. [Diagram 3] FIG. 3 shows a schematic perspective view of a ferrite tube core according to an exemplary embodiment of the present invention. [Figure 4] FIG. 4 illustrates a schematic perspective view of a suppressor choke in accordance with various exemplary embodiments of the present invention. [Diagram 5]FIG. 5 shows a schematic diagram of the relationship between magnetic permeability and frequency. [Figure 6] FIG. 6 shows a schematic diagram of the relationship between impedance and frequency. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0029] In the following description of Figures 1 and 2, a known ferrite tube core is shown, which is then contrasted in the ensuing description with a ferrite tube core according to an exemplary embodiment of the present invention.

[0030] 1 shows a known ferrite tube core 1 in the form of a solid core made of ferrite material. The ferrite tube core 1 is made of ferrite material.

[0031] FIG. 2 shows another known ferrite tube core 2 formed from individual core elements 2a-2f arranged one behind the other in a layered stacked arrangement, the core elements 2a-2f being formed congruent with one another.

[0032] FIG. 3 shows a schematic perspective view of a suppressor choke core configured as a ferrite tube core 3 according to various embodiments of the present invention. The ferrite tube core 3 includes two core elements 3a and 3b arranged concentrically with each other. This means that the core elements 3a and 3b are formed so that they can be arranged concentrically with each other. In particular, the inner diameter of the core element 3a is substantially equal to the outer diameter of the core element 3b. However, this is not a limitation, and the inner diameter of the core element 3a can also be larger than the outer diameter of the core element 3b to form a predetermined gap between both core elements 3a and 3b.

[0033] Although only two core elements are shown in the illustration of FIG. 3, this is not a limitation of the present invention and any number of hollow cylindrical core elements may be used to form the ferrite tube core, particularly 3, 4, 5, or more than 5 core elements.

[0034] In some exemplary embodiments, each of the hollow cylindrical core elements 3a and 3b may be formed as a ferrite core element or compact, in other words, each of the hollow cylindrical core elements 3a and 3b may be sintered separately. Optionally, at least one of the core elements 3a and 3b may be reworked and shaped into a desired shape, for example using a milling machine, which may reduce manufacturing tolerances in the manufacture of the ferrite tube core 3. After sintering and any further processing, the hollow cylindrical core elements 3a and 3b may be attached to each other in a gluing process with a glued joint. Alternatively, the hollow cylindrical core elements 3a and 3b may be attached to each other by a clamp, after sintering and any further processing. This ensures that the hollow cylindrical core elements 3a and 3b are permanently joined to each other. Also, all or each hollow cylindrical core element may be formed from a plurality of individual partial ring elements that may be glued or sintered to form the hollow cylindrical core element.

[0035] Alternatively, the hollow cylindrical core elements 3a and 3b are first provided as green bodies, which are shaped by dry or wet pressing of ferrite powder into the desired shape corresponding to the shape of the hollow cylindrical core elements 3a and 3b. The pressing can be one-sided, two-sided or isostatic pressing. The green bodies are then placed concentrically, one inside the other. A sintering process is then performed, and at the end of the sintering process, the hollow cylindrical core elements 3a and 3b are provided as sintered core elements together. In this process, a dispersion boundary occurs between the hollow cylindrical core elements 3a and 3b, which is due to the fact that during sintering, the ferrite material is dispersed from the green body corresponding to one of the hollow cylindrical core elements 3a and 3b into the green body corresponding to the other of the two hollow cylindrical core elements, thereby forming a more or less sharp dispersion boundary at the interface between the two green bodies. In this context, a dispersion boundary is understood to be a dispersed phase of two different materials that is generated during pressing in a multi-layer process. In a multi-layer process, two different materials are placed in a mold separated by an inlay / cavity. The materials are mixed together when removed. Generally, dispersion boundaries are undesirable and should be kept as low as possible in the manufacturing process. In some illustrative examples, the ratio of dispersion boundaries to wall thickness may be 1:100 or less.

[0036] In some exemplary embodiments, a suppressor choke core in the form of a ferrite tube core is formed as follows: First, a first tubular core green body (corresponding to a first hollow cylindrical core element) having an outer ring diameter is provided. A first material can be pressed in a first die to form a first tube core green body having a first outer ring diameter. The first tube core green body can be inserted into a larger second die, which is significantly larger than the first tube core green body, leaving additional space around the first tube core green body in the second die, into which material can be filled. In some exemplary examples herein, the first material can be different from the second material, but this is not a limitation, and the materials can be the same, particularly materials having the same composition, and these materials can differ in at least one physical parameter (for example, but not limited to, particle size). Both materials in the larger second die are pressed together, and a ferrite tube core green body is formed from two successively pressed tube core green bodies. The second material pressed around the first tube core green body forms a second tube core green body (corresponding to the second hollow cylindrical core element). The ferrite tube core green body may be subjected to further processing, such as a sintering process.

[0037] This process described above can be used repeatedly, for example, a ferrite tube core green body can be formed after repeating the above process steps at least once, such as placing a first tube core green body in a larger mold, filling the space around the first tube core green body placed in the larger mold with more material, pressing in the larger mold, etc. The obtained ferrite tube core green body can be repeatedly inserted into the larger mold as yet another tube core green body, filling the space around the yet another tube core green body placed in the mold with more material, pressing, etc.

[0038] Thus, the suppressor choke core employs a configuration in which successive hollow cylindrical core elements are disposed inside and successively wrapped or completely surrounded by other hollow cylindrical core elements, the hollow cylindrical core elements being wrapped by other hollow cylindrical core elements representing the inner core elements, which contribute to the subdivision of the wall thickness, thereby limiting eddy currents and improving broadband performance.

[0039] In some exemplary embodiments, at least one barrier layer has a high R spez The dielectric constant can be determined by a metal oxide layer having a resistance (e.g., >10 Ωm) or by one or more insulators (air gaps, adhesives).

[0040] In some exemplary embodiments, the dispersion-critical region can be formed in a multi-layer process such that the ratio of dispersion-critical region to wall thickness is at least 1:10 when the wall thickness is greater than 5 mm. For individually pressed green bodies, the ratio of dispersion-critical region can be 1:100.

[0041] In an alternative manufacturing process, the materials of the different core elements 3a and 3b can be filled into chambers of a mold separated by a cavity. After the chambers are filled with the materials of the core elements, the cavities can be removed and the materials in the chambers can be pressed. In this process, temperature can be applied during pressing and sintering can occur simultaneously. Alternatively, the sintering process can be performed at a later stage after pressing. Pressing processes include single-sided pressing, double-sided pressing and / or isostatic pressing.

[0042] According to some exemplary embodiments, the hollow cylindrical core elements 3a and 3b may be made of the same material. Alternatively, the hollow cylindrical core elements 3a and 3b may be made of different materials. Ferrite materials known for use in chokes, particularly suppressor chokes, may be used as materials for forming the core elements 3a and 3b.

[0043] In some exemplary embodiments, the material may have a permeability μi of at least 2000 and / or a resistivity of up to 5 Ωm. For example, a suitable material may be selected by balancing permeability and resistivity. In this case, the impedance at high frequencies may be intentionally increased by simultaneously selecting a relatively high permeability and a low resistivity. Exemplary materials are Fi340, Fi360, Fi410, Fi412, and Fi415.

[0044] Figure 4 shows a perspective view of a suppressor choke 4 according to some exemplary embodiments. The suppressor choke 4 is composed of a suppressor choke core in the form of a ferrite tube core 5 with hollow cylindrical core elements 5a and 5b arranged concentrically with respect to one another, and a current conductor 6 passing through the ferrite tube core 5. According to the illustration in Figure 5, the current conductor 6 is a busbar, for example a busbar of a busbar system. As an alternative to the illustrated embodiment, a wire winding (not shown) can be provided on the ferrite tube core 5 instead of the busbar 6, and the number of turns of the wire winding can be one or more.

[0045] 5 and 6, the relationship between the magnetic permeability (see FIG. 5) and the impedance (see FIG. 6) of the suppressor choke with a ferrite tube core (e.g., the above-mentioned suppressor choke 4) provided by the inventors is shown with respect to the frequency of the current flowing through the current conductor. In relation to FIG. 5 and FIG. 6, a comparison is made between the suppressor choke with a known ferrite tube core and the suppressor choke with a ferrite tube core according to the present invention.

[0046] The graphs in Figures 5 and 6 show the material properties (complex permeability μ', resistivity

number

[0047] FIG. 5 shows a logarithmic scale diagram of frequency (in kHz) plotted against permeability. It shows that graph 51 represents the permeability vs. frequency of a solid core, corresponding to solid core 1 of FIG. 1. For comparison, graph 52 shows a plot of permeability vs. frequency of a known laminated core, corresponding to ferrite tube core 2 of FIG. 2. As can be seen, the permeability of the laminated core is higher than that of the solid core over a wide frequency range. This situation was explained above in relation to the known laminated cores. These laminated cores have the smallest possible ratio of ferrite core area to circumference through which the current flows, which limits the generation of eddy currents compared to solid cores, but as can be seen from graph 52, they do not exhibit optimal broadband performance.

[0048] Furthermore, in FIG. 5, a graph 53 is drawn showing the relationship between magnetic permeability and frequency of the ferrite tube core according to the present invention, in particular the ferrite tube core corresponding to the ferrite tube core 3 in FIG. 3. In this context, the magnetic behavior of the ferrite tube core corresponding to the graph 53 is comparable to that of the laminated core corresponding to the graph 52. Compared with the known ferrite cores of the graphs 51 and 52, the ferrite tube core corresponding to the graph 53 achieves high magnetic permeability over a wide frequency range while the structure of the ferrite core is simple (the ferrite tube core 3 in FIG. 3 has two core elements, whereas the ferrite tube core 2 in FIG. 2 has six core elements). As shown by the graph 52 in FIG. 5, compared with the laminated core, the ferrite tube core 3 in FIG. 3 has a relatively low degree of fragmentation compared with the laminated core, and therefore is more cost-effective to manufacture. The structure of the ferrite tube core 3 in FIG. 3 is a rectangle with a large aspect ratio and a small area, which is advantageous in suppressing eddy current losses compared with the known laminated core structure, while at the same time providing a favorable wideband performance. According to the inventors' findings, this advantage has been achieved by dividing the ferrite core 3 of FIG. 3 into core elements 3a and 3b, which are inserted into each other like sleeves to form an onion structure.

[0049] In an exemplary embodiment, as shown in FIG. 5, the ferrite tube core 3 of FIG. 3 has a magnetic permeability, e.g., μ, of more than 1500 in a frequency range up to 20 kHz. r >1500, and the high permeability in this frequency range is substantially maintained in the high permeability range. Essentially, the permeability shown in FIG. 5 is essentially constant in the range of 1 kHz to 20 kHz, so that the permeability in the frequency range up to 10 kHz is greater than 9000 (e.g., μ r >9000). Furthermore, the permeability in the frequency range up to 50 kHz is greater than 2000, e.g. r >2000, preferably greater than 3000, e.g. r >3000, more preferably greater than 4000, e.g. r>4000. Furthermore, the permeability in the frequency range up to 100 kHz is greater than 2000 (for example, μ r >2000).

[0050] In certain exemplary embodiments herein, core elements 3a and 3b of Fig. 3 that are inserted into one another to form the onion structure of the ferrite tube core 3 of Fig. 3 can be bonded together to form a high impedance positive connection between these core elements. In contrast, the laminated structure of the known laminated core shown in graph 52 of Fig. 5 requires additional processing after sintering, such as grinding and gluing, as described above.

[0051] Referring to FIG. 6, a graphical representation of the impedance vs. frequency of the various ferrite tube cores of FIGS. 1-3 is shown. Here, graph 61 shows the impedance vs. frequency of a solid core, graph 62 shows the impedance vs. frequency of a laminated core corresponding to the ferrite tube core 2 of FIG. 2, and graph 63 shows the impedance vs. frequency of a ferrite tube core corresponding to the ferrite tube core 3 of FIG. 3. As can be seen from FIG. 6, the impedance of the solid ferrite tube core corresponding to graph 61 is smaller in a wider frequency range than the impedance of the ferrite tube cores of FIGS. 2 and 3 corresponding to graphs 62 and 63. In particular, the impedance behavior of the ferrite tube core corresponding to FIG. 3 is similar to that of the ferrite tube core of FIG. 2. However, the preferred impedance behavior corresponding to graph 63 can already be achieved even with a smaller number of core elements. For example, the ferrite tube core of FIG. 2 shows six layers of core elements. This means that the manufacturing effort increases, and therefore the ferrite tube core according to the present invention achieves the preferred magnetic behavior shown in FIGS. 5 and 6 with less manufacturing effort even with a smaller number of core elements. This allows for the provision of a suppressor choke with improved performance and better broadband performance in a simple manner with fewer manufacturing efforts.

[0052] 6, the ferrite tube core 3 of FIG. 3 may have an impedance of more than 580 Ω / m, preferably more than 600 Ω / m, and more preferably more than 700 Ω / m, in an exemplary embodiment measured by the inventors in the range of 10 kHz to 100 MHz. Furthermore, the ferrite tube core 3 of FIG. 3 may have an impedance of more than 390 Ω / m, preferably more than 400 Ω / m, in an exemplary embodiment measured by the inventors in the range of 5 kHz to 100 MHz.

[0053] In summary, the present invention provides a ferrite tube core constructed from sleeves inserted into each other to form an onion structure, with a similar degree of subdivision, and with a significantly higher wideband performance than, for example, known laminated cores. In a specific, non-limiting example, two ferrite tube cores inserted into each other can have a better wideband performance compared to a ferrite tube core of the same shape with a six-layer laminated structure.

[0054] In the manufacture of sintered hollow cylindrical ferrite core elements, the inventors have recognized that the dimensional tolerance of the sintered hollow cylindrical ferrite core elements depends mainly on shrinkage and distortion. Generally, in the sintering process, contact formation and contact growth between adjacent particles of the powder material or green body to be sintered occurs in the early stage of the sintering process during the heating period. In the intermediate stage of the sintering process, also known as the "shrinkage stage", shrinkage occurs at the sintering temperature (about 80% of the melting temperature) and sometimes under the influence of pressure during the sintering process, the shrinkage is maximum in the region of isothermal sintering, and after exceeding the maximum value, the shrinkage decreases more nonlinearly. The sintered body formed in the sintering process then undergoes a further decrease in shrinkage to reach the density of a solid in the final stage, and at the end of the sintering process, a compact is formed.

[0055] For hollow cylindrical ferrite core elements made of the same material, this means that the shrinkage can be neglected for different core elements using the same material, since the shrinkage is similar for the same material, which means that only the distortion, which depends on the sintering process and may be affected by temperature and cooling time, is taken into account.

[0056] On the other hand, for hollow cylindrical ferrite core elements made of multiple different materials, since the hollow cylindrical ferrite elements are manufactured from different materials, the inventors propose to pre-determine the batch shrinkage and take these results of the determined batch shrinkage values ​​into account during manufacturing in order to optimize the manufacturing process. Furthermore, depending on the sintering process with respect to the cooling time, the distortion can be affected to a known extent.

[0057] In various embodiments, the inventors have recognized that the broadband performance of the ferrite tube core according to the present invention depends on the properties of the distribution layer or adhesive joint between the different core elements. In particular, it has been recognized that the broadband performance is directly proportional to the resistance of the separation layer. The thickness of the separation layer is less than 1×10 6 Ω or 1×10 2 It can be determined based on the resistivity of the insulator material (air, epoxy resin / glue, metal oxide) and the barrier layer resistance, which is greater than Ωm.

Claims

1. A suppressor choke core comprising at least two hollow cylindrical core elements (3a, 3b; 5a, 5b), one of said hollow cylindrical core elements (3b; 5b) is disposed at least partially contiguously within another of said hollow cylindrical core elements (3a; 5a); The hollow cylindrical core elements (3a, 3b; 5a, 5b) are permanently bonded together to form a ferrite tube core (3; 5).

2. 2. The suppressor choke core according to claim 1, wherein the hollow cylindrical core elements (3a, 3b; 5a, 5b) are arranged concentrically and successively with one another.

3. 3. The suppressor choke core according to claim 1 or 2, wherein the at least two hollow cylindrical core elements (3a, 3b; 5a, 5b) are sintered and / or bonded together.

4. 3. A suppressor choke core according to claim 1 or 2, wherein the hollow cylindrical core elements (3a, 3b; 5a, 5b) are made from the same material.

5. 3. A suppressor choke core according to claim 1 or 2, wherein the hollow cylindrical core elements (3a, 3b; 5a, 5b) are made of different materials.

6. 3. A suppressor choke core according to claim 1 or 2, wherein the ferrite tube core (3; 5) has an impedance of more than 580 Ω / m, preferably more than 600 Ω / m, and more preferably more than 700 Ω / m in the range of 10 kHz to 100 MHz.

7. A suppressor choke (4) for suppressing high frequency interference, A suppressor choke core according to claim 1 or 2; At least one current conductor (6) passing through the ferrite tube core (5); A suppressor choke (4).

8. The at least one current conductor (6) includes a bus bar passing through the ferrite tube core (5). A suppressor choke (4) according to claim 7.

9. 1. A method of forming a suppressor choke core, comprising: forming at least two hollow cylindrical core elements (3a, 3b; 5a, 5b) such that one of said hollow cylindrical core elements can be placed consecutively within another of said hollow cylindrical core elements; arranging the at least two hollow cylindrical core elements (3a, 3b; 5a, 5b) in an arrangement in which one of the hollow cylindrical core elements is disposed consecutively within another of the hollow cylindrical core elements; permanently fixing said at least two hollow cylindrical core elements (3a, 3b; 5a, 5b) in said arrangement; A method for providing

10. 10. The method of claim 9, wherein said arranging step comprises arranging said hollow cylindrical core elements (3a, 3b; 5a, 5b) concentrically and successively with respect to one another.

11. The steps forming the at least two hollow cylindrical core elements (3a, 3b; 5a, 5b) The method includes providing said at least two hollow cylindrical core elements (3a, 3b; 5a, 5b) in a compressed green body, the permanently fixing step comprises sintering the green body.

11. The method according to claim 9 or 10.

12. the step of forming the at least two hollow cylindrical core elements (3a, 3b; 5a, 5b) comprises providing the at least two hollow cylindrical core elements (3a, 3b; 5a, 5b) as compressed green bodies and then sintering the green bodies; the permanent fixing step comprises gluing the at least two hollow cylindrical core elements (3a, 3b; 5a, 5b) together or continuously pressing the green body together; 11. The method according to claim 9 or 10.

13. finishing the at least two hollow cylindrical core elements (3a, 3b; 5a, 5b) after sintering by milling the at least two hollow cylindrical core elements (3a, 3b; 5a, 5b) into a desired shape, The method of claim 12.

14. the at least two hollow cylindrical core elements (3a, 3b; 5a, 5b) are made of different materials; The method comprises: sintering in accordance with a predetermined shrinkage of the batch of hollow cylindrical core elements and / or adjusting the standing time and cooling time during sintering to reduce distortion. The method of claim 11.

15. said at least two hollow cylindrical core elements (3a, 3b; 5a, 5b) being made of the same material; The method comprises: Further comprising adjusting the standing time and cooling time during sintering to reduce distortion. The method of claim 11.

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