Filter choke, method for manufacturing filter choke, and electrical device

Abstract

The present application relates to a filter choke (10) for use in an EMI filter, A closed magnetic core (20) having two core legs (21, 22) and configured to be assembled from at least two core segments (23); at least two bobbins (30), each of which comprises a base flange (31) and a tubular section (32a, 32b) extending perpendicularly from the base flange (31), the tubular section (32a, 32b) comprising an opening (33) for receiving one of the two core legs (21, 22); a coil (40) formed by a conductor (41) having a plurality of windings disposed around the tubular sections (32a, 32b) of each bobbin (30); A filter choke (10) comprising: The present invention discloses a filter choke (10) characterized in that, in an assembled state, the bobbins (30) are arranged in a stack such that their openings (33) are coaxially aligned with one another and one of the core legs (21, 22) extends through the opening (33), each bobbin (30) has at least two first mating elements (35) arranged on opposing edges (34) of its base flange (31), the first mating elements (35) of a first bobbin (30) configured to engage with the first mating elements (35) of an adjacent second bobbin (30) to removably secure the two bobbins (30) together. The present application further discloses a method for manufacturing the filter choke (10), as well as an electrical device comprising the filter choke (10).

Description

[Technical field]

[0001] The present invention relates to a filter choke for use in electromagnetic interference (EMI) filters. In particular, the present invention relates to a filter choke which, on the one hand, provides highly reproducible magnetic properties, especially in mass production, and, on the other hand, is easy to assemble, even when wires with large cross-sectional areas are used. The filter choke can be used in various devices, including differential mode filters and common mode filters, but is intended in particular for use as a common mode filter choke. The present invention also relates to an electrical device comprising the respective filter choke and to a method for manufacturing the filter choke. [Background technology]

[0002] Various electrical devices, such as switched mode power supplies, typically emit electromagnetic radiation during normal operation. To reduce this electromagnetic radiation at least below the values ​​defined in the relevant electrical standards, EMI filters are usually implemented within the device. EMI filters are therefore necessary components to ensure the electromagnetic compatibility (EMC) of devices during operation. EMI filters comprise filter chokes that can be configured as differential mode filter chokes or common mode filter chokes, depending on the radiation mode to be filtered.

[0003] The filter choke may comprise a magnetic core and at least two coils, each of which comprises an electrical conductor arranged around a leg of the magnetic core in the form of one or more windings. Since it is frequently required that the magnetic core has a low magnetic resistance, the core is designed as a closed magnetic core in the form of a one-piece part. The coil is then usually manufactured by manually winding an electric wire around the magnetic core. However, the manual manufacturing process is relatively labor-intensive, especially when electric wires with a large cross-sectional area are used, which is typically the case when a low ohmic resistance of the conductor is required. The manual manufacturing process also results in a relatively low reproducibility in the successive manufacture of several filter chokes, which theoretically include the same design. The size of the parts is also large. It is therefore desirable to provide an optimized design of the filter choke.

[0004] CN203858954U discloses a choke comprising a core set, two winding frames, a partitioning part, and a winding. The core set comprises a first core and a second core. Both ends of the first core and both ends of the second core are separably connected to form a closed shape. Each winding frame comprises a winding frame body provided with a core passage through which the core set can pass. The partitioning part can be fixed to and combined with the two winding frames. The winding is wound on the two winding frames.

[0005] JP6458720B2 discloses a reactor consisting of a core and a bobbin with a coil arranged around the core. The bobbin consists of a first body part and a second body part. The first body part consists of a first flange including an opening through which the core passes, a first cylindrical member arranged on one side of the first flange, and a first arm member. The second body part consists of a second flange including an opening through which the core passes, a second cylindrical member arranged on one side of the second flange, and two second arm members. The bobbin is formed by fitting the first arm member between the two second arm members.

[0006] JPH0562020U discloses a structure including an assembly of a terminal block and a bobbin. This assembly is structured such that a plurality of locking projections are provided on the reel. Locking recesses and projections are used to engage and fix the reel to another reel, or to the reel to a terminal block. This provides a bobbin that combines a bobbin portion having one or more sections with a terminal block having various pins. Summary of the Invention

[0007] It is an object of the present invention to provide a filter choke for use in an EMI filter which addresses, eliminates or mitigates at least one of the above mentioned disadvantages. In particular, the filter choke shall have highly reproducible magnetic properties within multiple filter chokes manufactured according to the same design, combined with a simple method of assembly.

[0008] According to the present disclosure, the object of the present invention is solved by a filter choke having the features of independent claim 1. Dependent claims 2 to 13 relate to preferred embodiments of the filter choke according to the invention. Claim 14 relates to an electric device comprising the filter choke of the invention. Claim 15 relates to a method for manufacturing the filter choke.

[0009] According to the present invention, a filter choke for use in an EMI filter comprises: a closed magnetic core having two core legs, the closed magnetic core being configured to be assembled from at least two core segments; The filter choke comprises at least two bobbins, each bobbin including a base flange and a tubular section extending perpendicularly from the base flange, the tubular section including an opening for receiving a first of the two core legs. The filter choke further comprises a coil formed by an electrical conductor having a plurality of windings disposed about the tubular section of each bobbin. One of the at least two bobbins is configured such that the coil in a pre-wound state is attachable to a respective one of the tubular sections of the at least two bobbins, in particular along the axial direction of the tubular section, characterized in that in the assembled state of the filter choke, the bobbins are arranged in a stack such that their openings are coaxially aligned with one another and one of the core legs extends through the opening. Furthermore, each bobbin comprises at least two first mating elements arranged on opposite edges of its base flange. In the assembled state of the filter choke, the first mating elements of the first bobbin are configured to engage with the first mating elements of the adjacently arranged second bobbin to removably fix the two bobbins together. Thus, in the assembled state of the filter choke, the coil is arranged between adjacent bobbins, i.e. between the base flange of the first bobbin and the base flange of the adjacent second bobbin. The arrangement of the coil between the base flanges of the adjacent bobbins may be such that in the assembled state of the filter choke, the coil is slightly pressurized in its axial direction by the base flange of the adjacent bobbin. This pressurization makes the filter choke in the assembled or pre-assembled state more mechanically stable than if the coil was not pressurized, and therefore optimizes the reproducibility of the magnetic properties of the filter choke in general and during handling in particular.

[0010] The feature that one of the at least two bobbins is configured such that a pre-wound coil can be attached to a respective one of the tubular sections of the at least two bobbins can provide the possibility of a sliding guided movement of the coil in the respective tubular section, at least in the state before the final assembly of the filter choke. In particular, at least at the end of the tubular section into which the coil is inserted, there is no barrier that prevents the coil from being attached to the tube end. Preferably, each end section can include a conical design, which allows a simple way of attaching the coil on the tubular section. Also, apart from the end, a base flange of the bobbin is provided. For example, it can be provided near the other end of the tubular section opposite the end, on which the pre-wound coil is attached during assembly. Alternatively, it can be provided near the middle of the tubular section. In any of these cases, it is ensured that in the assembled state of the filter choke, the pre-wound coil is placed between the base flanges of the adjacent bobbins and, optionally, slightly pressurized.

[0011] Within the scope of the present invention, not only one, but each of the at least two bobbins can be configured such that a pre-wound coil can be attached to each tubular section of the at least two bobbins. Needless to say, the openings of the tubular sections, in particular the openings of each tubular section, are also present at their respective positions in the base flange, not only in the tubular section but also through the base flange, so that an axially continuous through-hole is provided for each tubular section. The filter choke may also include more than two bobbins, for example three or even more bobbins, which are arranged in a stack one above the other, adjacent bobbins being removably fixed to each other.

[0012] The feature that one of the two core legs extends through the coaxially arranged openings of the stacked bobbins may imply that a single core segment also penetrates these openings. However, this is only one option for realizing the respective feature. In an alternative embodiment, it is also possible that in the assembled state of the filter choke, the gap between the two core segments forming the magnetic core is arranged between the two bobbins. In that embodiment, each one of both core segments penetrates only one of the openings. In yet another embodiment, it is also possible that in the assembled state of the filter choke, one and / or two of the core segments only partially penetrate one opening, so that the gap formed between them is localized inside the tubular section of a particular bobbin.

[0013] The at least two bobbins are usually made of an insulating material (e.g. a synthetic resin material). The manufacturing process of the bobbins can include an injection molding process. The injection molding process allows to guarantee small tolerances on the dimensions of the bobbins, which is advantageous in terms of the reproducibility of the magnetic properties of the filter choke. The magnetic properties of the filter choke can be changed by changing the number of bobbins actually present in a modular manner in the filter choke, and therefore by changing the number of pre-wound coils. In particular, if the filter choke requires an increase in the inductance value, the number of stacked bobbins and also the number of pre-wound coils can be increased. Thus, within the scope of the present invention, the filter choke in an embodiment can comprise more than only two bobbins, for example three, four or even more bobbins. It is not necessary for the at least two bobbins to have substantially the same design, which is, however, advantageous in order to keep the investment at a relatively low level, since only a single injection mold is required. However, depending on the application, it may be advantageous to use different designs of the at least two bobbins. In this case, the design of the different bobbins can differ, in particular with regard to the length of the tubular section for each bobbin, so that different numbers of pre-wound coils can be arranged in the different tubular sections, however, it is advantageous to keep the lateral dimensions of the bobbin (in particular its base flange) constant.

[0014] Since the closed magnetic core is configured to be assembled from at least two core segments, laborious manual manufacturing methods are no longer required. Thus, according to the invention, the design of the filter choke makes it possible to manufacture the filter choke in a simple and easy way. providing at least two core segments configured to be assembled into a closed magnetic core having two core legs; providing a first bobbin and a second bobbin, each bobbin including a base flange and a tubular section extending perpendicularly from the base flange, the tubular section including an opening for receiving a first of two core legs; winding the conductor to form at least two coils by using an automated winding process; placing a pre-wound coil onto the tubular section of each bobbin; placing the first bobbin in a stacked relationship with the second bobbin and removably securing the first bobbin to the second bobbin with their openings coaxially facing each other, the terminals of the coil being substantially in place; inserting the core segments into openings in the bobbin to form a closed magnetic core; Includes.

[0015] The design of the filter choke allows the use of highly automated manufacturing methods. In particular, automated winding techniques can be used to wind the conductor, which is advantageous for manufacturing the coil in a reproducible and cost-effective manner. This is particularly advantageous when the conductor has a large cross section and is very difficult and unreproducible to wind by hand. One or both of the bobbins are configured such that the coil can be attached to one tubular section of each of the at least two bobbins, and the winding of the coil is performed before being placed on the bobbin and on the core legs, thus eliminating the mechanical stresses and their adverse effects on the magnetic core during winding that are usually present when using manual winding processes. The magnetic core is configured to be assembled from at least two core segments and thus comprises at least one gap, but the adverse effect of the gap on the magnetic properties of the assembled magnetic core (here, an increase in the magnetic reluctance of the magnetic core) can be reduced by designing the core segments to provide a bypass path for the magnetic flux around the at least one gap in the assembled state of the magnetic core. This is explained in more detail in Figures 4a and 4b.

[0016] In a preferred embodiment of the filter choke, each bobbin comprises two tubular sections extending vertically from the base flange, each of the tubular sections comprising an opening for receiving a different one of the two core legs. The feature that each bobbin comprises two tubular sections should be understood to mean that in addition to the above-mentioned tubular sections, each bobbin comprises a further tubular section extending vertically from the base flange. For each bobbin, the further tubular section can be arranged adjacent to the tubular section. In this case, a respective coil of the coil and the further coil, formed by an electrical conductor and including a plurality of windings, is arranged around each tubular section of each bobbin. Here, at least one of the two bobbins is configured such that each coil in a pre-wound state is attachable to an associated one of the two tubular sections, in particular along the axial direction of the tubular section. In this embodiment, in the assembled state of the filter choke, the coil is arranged between the base flanges of the adjacent bobbins, optionally in a slightly pressurized manner. Both or all of the at least two bobbins may be configured such that each pre-wound coil can be attached to the two tubular sections of each of the at least two bobbins. The two tubular sections may include axial directions oriented substantially parallel to each other. This may be particularly true when the magnetic core includes a closed rectangular design with parallel oriented core legs at opposite portions of the magnetic core. The magnetic core may also be configured to have a toroidal shape in the assembled state.

[0017] In one embodiment, each bobbin of the filter choke may include a guide element arranged on the bottom and / or top surface of its base flange. The guide element may be configured to position and / or align at least one terminal or each terminal of a pre-wound coil formed by an electrical conductor and arranged on the tubular section in the assembled state of the filter choke. Preferably, each bobbin may include a guide element such that each terminal of each coil present in the assembled filter choke is aligned with each other and located in a predetermined position relative to the assembled filter choke. Easy assembly of the filter choke with other electrical components in an electrical device, in particular the assembly of the filter choke on a printed circuit board (PCB), may be assisted by the guide element.

[0018] In one embodiment of the filter choke, the at least two first mating elements of the first bobbin can be configured to form a snap fit with a respective first mating element of the adjacent second bobbin when the filter choke is assembled. In particular, the first mating elements of each of the first and second bobbins can include a snap fit portion and / or a corresponding mating portion. The snap fit can comprise a hook / loop design in which a "hook" as a snap fit portion engages with a corresponding "loop" as a mating portion. For each first mating element, the snap fit portion and the snap fit mating portion can be designed to extend perpendicularly to the base flange and in opposite axial directions from an edge of the base flange. In a preferred embodiment of the filter choke, the at least two bobbins can be designed substantially identical to each other by providing such designed portions and mating portions in the first mating elements of each of the bobbins. By designing the at least two bobbins substantially identical to each other, the investment in the injection mould required to manufacture the bobbins can be minimised. This also applies when the at least two bobbins differ only in the length of their respective tubular sections. Thus, the expression "substantially identical" is meant here to encompass bobbin designs that are identical for the at least two bobbins apart from the difference in the length of the tubular sections.

[0019] In one embodiment of the filter choke, one or two base flanges of the at least two bobbins, in particular the outer bobbins of the at least two bobbins in the assembly of the filter choke, may comprise two second mating elements for releasably engaging with corresponding mating elements of a core clip, the core clip being configured to fix at least one, preferably two or more, of the multiple core segments of the magnetic core in the assembly of the filter choke. The assembly of the filter choke, in particular the fixation of the magnetic core segments in the sub-assembly of the magnetic core, can be easily achieved using the core clip(s).

[0020] The filter choke may further comprise a lid, preferably made of an insulating material and having substantially the same shape as the base flange of the bobbin. In particular, the periphery shape of the lid is identical to that of the base flange of the bobbin. In the assembled state of the filter choke, the lateral construction space required for the lid is therefore substantially equal to that required for the base flange. The lid serves as an insulating means, which ensures that undesired electrical contact between the outer coil(s) and the magnetic core is prevented. The lid may be configured to be removably fixed to the upper or outer one of the first and second bobbins in the assembly of the filter choke. Fixation to the respective bobbin may also be achieved by providing a respective snap-fit ​​portion on one side of the lid, which is configured to engage with a free snap-fit ​​mating portion of the adjacently arranged bobbin. The lid may also comprise the same number of openings in similar positions compared to each one of the bobbins in the filter choke, so that the lid is also configured to receive at least one core leg or two core legs of the magnetic core. However, in contrast to the bobbin design, one side of the lid part is provided with a substantially flat surface design without tubular sections extending in the respective direction. However, on that side there may be a second mating element configured to engage with a corresponding mating element of a further core clip of the filter choke. By providing two core clips on both sides of the filter choke, the entire assembly can be securely fastened in a simple manner.

[0021] Since the magnetic core of the filter choke is configured to be assembled from a number of core segments, gaps exist in the magnetic core, which usually increase its magnetic reluctance. Since the relevant applications of the filter choke often require that the magnetic core has a low magnetic reluctance, an increase in magnetic reluctance is an undesirable effect. This negative effect is conventionally only slightly mitigated by polishing the outer surface of some of the core segments, which involves an additional labor-intensive process. However, according to the present application, the magnetic core of the filter choke can be provided with low magnetic reluctance bypass paths around the gaps, optionally around each gap. Thus, the negative effect can be minimized or even eliminated without laborious polishing.

[0022] Specifically, the magnetic core of the filter choke has a gap plane normal oriented substantially parallel to the magnetic flux direction during operation of the filter choke. In the case of a closed magnetic core assembled from several core segments, the magnetic flux during operation of the filter choke and therefore the gap plane normal The bypass path may also be oriented in a circumferential or outer circumferential direction of the substantially closed magnetic core. And the bypass path may comprise an overlap region between two core segments disposed adjacent to the gap, the overlap region being such that during operation of the filter choke, the interface normal of the overlap region is inclined relative to the interface normal of the core segment. In the case of a closed magnetic core assembled from multiple core segments, the magnetic flux is substantially oriented in the circumferential or peripheral direction of the closed magnetic core, and therefore the interface normal TIFF2024542166000005.tif8170 are oriented substantially perpendicular to the circumferential or peripheral direction of the closed magnetic core. The close contact of the core segments is provided by the overlapping areas between the core segments, through which the magnetic flux can easily penetrate from one core segment to the other. Also, the tendency of the flux to penetrate from one core segment to the other depends on the size of the overlapping area. In particular, said penetration becomes easier as the area of ​​the overlapping area increases. Thus, the reluctance of the bypass path, and thus of the magnetic core, decreases with the increase in the area of ​​the overlapping area. Thus, by designing the geometry of the core segments, and in particular their overlapping areas, the specific reluctance of the magnetic core can be designed.

[0023] The overlap region can be formed between two core segments that also form a gap (this is the case for the magnetic core disclosed in FIG. 4a). However, it is also possible for the magnetic core to comprise at least three or more core segments. In that case, it is possible for a gap to be formed by a first core segment and a second core segment, two overlap regions adjacent to the gap being formed, from which one overlap region is formed between the first core segment and a third core segment, and another overlap region is formed between the third core segment and the second core segment (see FIG. 4b).

[0024] In one embodiment, the magnetic core in the assembled state of the filter choke may comprise at least four core segments arranged in at least two layers arranged one above the other. Each layer may include a closed magnetic subcore having substantially the same geometric shape formed from at least two core segments, the closed subcores being coaxially aligned with each other. In that case, the core segments of the subcores in different layers are arranged such that all gaps having a gap surface normal oriented substantially parallel to the magnetic flux are arranged offset from each other in the different subcores. With this design feature, a low reluctance bypass path around each gap in the first layer is led along the core segment in the adjacent second layer and is arranged above or below the gap in the first layer. Furthermore, a low reluctance bypass path around each gap in the second layer is led along the core segment in the adjacent first layer and is arranged above or below the gap in the second layer.

[0025] Regardless of whether the magnetic core includes one or more layers and whether it includes two or more core segments, the multiple core segments can include different core materials. Thus, each individual core segment is formed from only a single core material, but the core materials of at least two individual core segments of the multiple core segments may be different from each other. If the magnetic core includes multiple layers, in one embodiment, each layer can include only a single core material, but the core materials of at least two different layers may be different from each other. In an alternative embodiment, one layer, multiple layers, or each layer can include at least two core segments with different core materials. By selecting different core materials for the core segments, a greater degree of freedom can be achieved to achieve target values ​​of certain magnetic properties of the filter choke, for example by selecting material A for the first core segment and material B for the second core segment. Thus, the inductance of the filter choke can be adjusted to the required value better than in the case of a magnetic core with the same material for each core segment.

[0026] In one embodiment of the filter choke, the conductor used to wind the at least two coils comprises a rectangular wire. Optionally, the at least two coils are formed by winding the rectangular wire around its narrow edge. By winding the rectangular wire, in particular by winding the rectangular wire around its narrow edge, it is possible to produce coils (also called "edge wound coils") that have a relatively low ohmic resistance in combination with a relatively high winding density. This advantageously reduces the component size of the filter choke. The DC resistance of such "rectangular wire coils", in particular "edge wound coils", can be kept low, so they are preferably used for filter chokes in power electronic electrical equipment (e.g. DC / DC converters or DC / AC inverters). Using conventional manual and labor-intensive winding techniques, it is often not possible to produce such edge wound coils. However, this is not a problem for the filter choke according to the present application, because the method of producing the filter choke includes the act of forming the coils using automated winding techniques.

[0027] The electrical device according to the invention is characterized in that it comprises an EMI filter comprising a filter choke according to the invention. The filter choke in the device can be configured to operate either as a "differential mode" filter choke or as a "common mode" filter choke. The electrical device can be a power electronic device, in particular a DC / AC inverter or a DC / DC converter. The effects caused in the electrical device are similar to those already described in combination with the filter choke and the method for producing it. For the effects related to the electrical device, reference is therefore made to the relevant sections. [Brief description of the drawings]

[0028] The present invention will be further explained and described with reference to preferred exemplary embodiments shown in the drawings.

[0029] [Figure 1]Figure 1a shows an exemplary embodiment of a bobbin that can be used with the filter choke shown in front view, and Figure 1b shows the bobbin of Figure 1a shown in rear view. [Diagram 2] FIG. 2 shows an embodiment of a first bobbin and a second bobbin in a pre-assembled state. [Diagram 3] Figure 3a shows a first embodiment of a filter choke according to the invention in an exploded view, and Figure 3b shows the filter choke of Figure 3a in an assembled state. [Figure 4] Figure 4a is a schematic diagram of the gap and its low reluctance bypass path in a first embodiment of a magnetic core, and Figure 4b is a schematic diagram of the gap and its low reluctance bypass path in a second embodiment of a magnetic core. [Diagram 5] Figure 5a shows an exemplary embodiment of a magnetic core for use in a filter choke in an exploded view, and Figure 5b shows the magnetic core of Figure 5a in an assembled state. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0030] In the following, the design of an exemplary embodiment of a bobbin 30 that can be used in an embodiment of a filter choke 10 according to the present invention will be described in more detail. The description refers to Figures 1a and 1b, where Figure 1a shows a bobbin 30 in a front view and Figure 1b shows the same bobbin 30 in a rear view.

[0031] The bobbin 30 comprises a planar base flange 31 and two tubular sections 32a, 32b extending from a front surface 36b of the base flange 31 in a direction perpendicular to the base flange 31. Each tubular section 32a, 32b comprises an inner opening 33. The base flange 31 also comprises respective openings corresponding to and aligned with the inner openings 33 of the tubular sections 32a, 32b, thereby providing each tubular section with a continuous through-hole that also extends through the base flange 31. Each opening 33 is configured to receive a different core leg 21, 22 of the magnetic core 20 (see Figs. 3a, 3b). In Figs. 1a and 1b, each opening is divided by a partition 50, but said partition 50 is merely optional. Therefore, other embodiments of the bobbin 30 may not comprise said partition 50 inside the opening 33.

[0032] The bobbin 30 further comprises a plurality of first mating elements 35 arranged on opposing edges 34 of the base flange 31. As an example, the bobbin 30 shown in Figs. 1a and 1b comprises four first mating elements 35, two on each opposing edge 34. The bobbin 30 is configured to removably secure another substantially identical further bobbin to the bobbin 30 via the first mating elements 35. Each first mating element 35 includes a portion 38a and a corresponding mating portion 38b of a snap fit 38 that is formed when the first mating elements 35 of the bobbin and the further bobbin 30 are engaged. As an example, the snap fit 38 is formed as a "hook-loop" snap fit. That is why each portion 38a is formed as a hook, whereas the corresponding mating portion 38b is formed as a loop. However, other designs of the snap fit are also possible, for example a "hook-undercut" snap fit design.

[0033] Arranged on the rear face 36a of the base flange 31 are two second mating elements 39a which are configured to engage with corresponding mating elements 39b of the core clip 24 in the assembled state of the filter choke 10 (see Figure 3b). The front face 36b and / or the rear face 36a may also be provided with guide elements configured to guide and / or align coil terminals 42a, 42b of a pre-wound coil 40 in the assembled filter choke 10, the function of which will be explained in more detail in Figure 2.

[0034] 2 shows an embodiment of a pre-assembly of a first bobbin 30 and a second bobbin 30' substantially identical to the first bobbin 30. Both bobbins are arranged one above the other and removably fixed to each other via the first mating elements 35. In particular, each portion 38a of the first mating elements 35 of the second bobbin 30' engages with a corresponding mating portion 38b of the first mating elements 35 of the first bobbin 30. Two pre-wound coils 40 formed by electrical conductors 41 and placed on the tubular sections 32a, 32b of the first bobbin 30 before pre-assembly are compressed and thereby fixed between the bobbins via the fixation of the bobbins 30, 30'. Each coil 40 includes two terminals 42a, 42b that are positioned and aligned in the pre-assembly via guide elements 43a-43c and 43d-43f that extend from the front and / or rear of each bobbin 30, 30'. The close tolerances that can typically be achieved by injection molding the bobbins 30, 30' ensure precise alignment and positioning of the terminals 42a, 42b.

[0035] The assembly of an exemplary embodiment of a filter choke will now be described with reference to Figures 3a and 3b, where Figure 3a shows an exploded view of the filter choke 10 and Figure 3b shows the filter choke 10 of Figure 3a in an assembled state. The filter choke 10 comprises three substantially identical bobbins 30. By way of example, each bobbin is also designed identically to the bobbin 30 shown in Figures 1a and 1b. The filter choke 10 further comprises six pre-wound coils 40, each of which comprises a conductor 41 formed by a rectangular wire. By way of example, the pre-wound coils 40 are formed as so-called "edge-wound coils" manufactured by winding the rectangular wire 41 around its narrow edge. The filter choke 10 also comprises a lid 37 configured to be attached and removably fixed to the outer bobbin 37 (the left bobbin 30 in Figure 3a). The design of the lid 37 is similar to that of the bobbins 30, at least with respect to its lateral dimensions as well as the geometric shape of its rear surface. However, the front surface of the lid 37 is substantially flat. The lid 37 also comprises two openings 33 at corresponding positions as in the bobbin 30. Each opening 33 in the lid 37 is arranged to accommodate a different one of the core legs 21, 22 of the magnetic core 20. The magnetic core 20 of the filter choke 10 is formed by four U-shaped core segments 23 arranged in two adjacent layers. Each layer comprises two U-shaped core segments 23 such that, in the assembled state of the filter choke 10, each layer comprises a closed magnetic sub-core 28a, 28b. The U-shaped core segments 23 have two different lengths such that, in the assembled state of the filter choke 10, the gap 26 formed in the magnetic sub-core 28a in the first layer is offset relative to the gap 26 formed in the magnetic sub-core 28a in the second layer. These offset gaps and the overlap regions formed by core segments 23 in different layers provide low reluctance bypass paths extending across each of the gaps 26 in the magnetic core 20 .The magnetic core therefore includes a total of four gaps 26, each gap having a gap plane normal oriented substantially parallel to the magnetic flux within the magnetic core 20 during operation of the filter choke 10. TIFF2024542166000006.tif10170, yet the magnetic reluctance of the magnetic core 20 can be kept relatively low.

[0036] When assembling the filter choke 10, each coil 40 is placed around a different one of the tubular sections 32a, 32b of several bobbins 30. After placing the coils 40 on the tubular sections 32a, 32b, each bobbin 30 is removably secured to an adjacent bobbin 30, thereby compressing the coils 40 between the adjacent bobbins and positioning / aligning the terminals 42a, 42b of the coils 40 in place relative to the overall assembly. The lid 37 is also removably secured onto the outer bobbin 30 via corresponding portions 38a and / or mating portions 38b of the snap fit, which are also located on opposing edges of the lid 37. The magnetic core 20 is then assembled by inserting the U-shaped core segments 23 into the lid 37 and the openings 33 of the bobbins 30. Finally, the core segment 23 of the magnetic core is secured to the outer bobbin 30 and also to the lid 37 by removably securing one of two core clips 24 on either side of the filter choke 10.

[0037] In the following, the operating principle of the low reluctance bypass path 25 will be described in more detail. In particular, FIG. 4a shows a schematic diagram of a cross section of a magnetic core 20 according to a first embodiment of the magnetic core 20. The cross section shows a gap 26 formed by a first core segment 23a and a second core segment 23b. The gap 26 has a gap surface normal oriented substantially parallel to the magnetic flux Φ. 4a, both adjacent core segments 23a, 23b are designed such that an overlap region 27 is provided adjacent to the gap 26. The overlap region 27 is aligned along the surface normal of the core segments 23a, 23b. TIFF2024542166000008.tif7170 are oriented such that they are oriented substantially perpendicular to the direction of the magnetic flux Φ during operation of the filter choke 10. In the overlap region 27, it is possible to provide a tight contact between both core segments 23a, 23b over a relatively large surface area (larger than at least the area associated with the gap 26). Thus, in the overlap region 27, the resistance to the penetration of the magnetic flux Φ from the first core segment 23a to the second core segment 23b is low, and the magnetic resistance to the penetration of the magnetic flux Φ from the first core segment 23a to the second core segment 23b and vice versa is low, at least significantly lower than the magnetic resistance when passing through the gap 26. This provides a low magnetic resistance bypass path 25 around the gap 26, as represented by the small arrows and dotted lines in FIG. 4a.

[0038] The penetration resistance of the magnetic flux Φ in the overlap region 27 depends on its lateral dimension, and typically the resistance decreases as the lateral dimension of the overlap region 27 increases, and therefore can be easily modified by targeting the mutual design of the core segments 23a, 23b.

[0039] Figure 4b shows a schematic diagram of the gap 26 and its low reluctance bypass path 25 in a second embodiment of the magnetic core 20. This situation is similar to that shown in Figure 4a. However, in the embodiment of Figure 4b, the magnetic core 20 comprises two adjacent layers, each layer being provided with closed magnetic subcores 28a, 28b, such that the closed subcores 28a, 28b are stacked one on top of the other. Although each subcore 28a, 28b represents a closed magnetic subcore, the gap 26 exists due to the fact that each subcore 28a, 28b is formed by at least two core segments 23a, 23b (in the first layer 28a) and at least two core segments 23c, 23d (not shown in Figure 4b) in the second layer 28b. The gaps 26 in the different subcores 28a, 28b are offset from one another such that adjacent to a gap in one of the subcores 28a, 28b there is always a continuous section of the core segment 23 of the other subcore 28b, 28a. Figure 4b shows by way of example the situation around such a gap 26 in the first layer 28a (in the first layer in Figure 4b).

[0040] Adjacent to the gap 26, at each of its locations, an overlap region 27 between two different core segments 23a-23c is formed. In particular, in FIG. 4b, on one side of the gap 26, an overlap region 27 is formed between the first core segment 23a and the third core segment 23c, while on the other side of the gap 26, a further overlap region 27 is formed between the second core segment 23b and the third core segment 23c. Based on the explanation provided in relation to FIG. 4a, this results in a low reluctance bypass path around the gap 26 starting from one side of the gap 26 in the first core segment 23a, passing through the overlap region 27 via the third core segment 23c, and further through the overlap region 27 into the second core segment 23b, and vice versa. In this embodiment, the low reluctance bypass paths 25 are routed around the gap 26 through core sections 23c, 23d of magnetic subcores in adjacently disposed subcores 28a, 28b, i.e., subcores 28a, 28b in adjacent layers. If more than two subcores 28a, 28b, or layers, are provided in the magnetic core 20, a respective bypass path 25 around the gap 26 is present in each adjacent subcore 28a, 28b.

[0041] In the following, an alternative embodiment of the magnetic core 20 is described compared to the one shown in Figures 3a and 3b. For the purpose of explanation, reference is made to Figures 5a and 5b, where Figure 5a shows the magnetic core 20 in an exploded view and Figure 5b shows the magnetic core 20 in a pre-assembled state. The magnetic core 20 is formed by two core segments 23. Each core segment 23a, 23b includes a U-shaped design with two U-shaped legs and a U-shaped base with a thickened central region. In the pre-assembled state of the core segments 23a, 23b, a closed magnetic core 20 is formed with a rectangular geometric shape (seen from a top view). Furthermore, in the pre-assembled state of the magnetic core 20 of Figures 5a, 5b, two gaps 26 between the two core segments 23a, 23b are formed on each U-shaped base (in other words, on each short side of the magnetic core 20). Furthermore, two overlap regions 27 are formed in the pre-assembled state, which overlap regions 27 extend along the U-shaped legs (in other words, along the core legs 21, 22). Bearing in mind the illustration given in Fig. 3a, this provides, for two gaps 26 (out of four) on one short side of the magnetic core 20, a magnetic bypass path 25 around each gap 26, as shown diagrammatically in Fig. 5b.

[0042] Although the magnetic core 20 of Figures 5a and 5b is configured for use as a magnetic core having only a single layer, it is alternatively possible to form the magnetic core 20 to include multiple magnetic cores, such as magnetic subcores 28a, 28b, with each subcore 28a, 28b disposed in a single one of the multiple layers. [Explanation of symbols]

[0043] 10 Filter Choke 20 Magnetic Core 21, 22 Core legs 23, 23a-23d Core Segment 24 Core Clips 25 Bypass Route 26 Gap 27 Overlap Area 28a, 28b subcore 30, 30' bobbin 31 Base flange 32a, 32b Tubular sections 33 Opening 34 Edge 35 Mating elements 36a back 36b front 37 Lid 38 Snap Fit 38a (Snap Fit) Part 38b (Snap fit) mating part 39a, 39b mating elements 50 Bulkhead 40 Coil 41 Conductors 42a, 42b terminals 43a~43f Guidance elements

Claims

1. A filter choke (10) for use in an EMI filter, the filter choke (10) comprising: a closed magnetic core (20) having two core legs (21, 22) and configured to be assembled from at least two core segments (23); at least two bobbins (30), each having a base flange (31) and a tubular section (32a, 32b) extending perpendicularly from the base flange, the tubular section (32a, 32b) having an opening (33) for receiving one of the two core legs (21, 22); a coil (40) formed by a conductor (41) having a plurality of windings disposed around the tubular section (32) of each bobbin (30); A filter choke (10) comprising: One of the at least two bobbins (30) is configured such that the pre-wound coil (40) is attachable to the tubular section (32) of a respective one of the at least two bobbins (30), and in the assembled state of the filter choke (10), the bobbins (30) are stacked such that their openings (33) are coaxially aligned with one another and one of the core legs (21, 22) extends through the opening (33), and each bobbin (30) has a base flange (31) 1. A filter choke (10) comprising at least two first mating elements (35) arranged on opposing edges (34) of adjacent bobbins (30), the first mating elements (35) of the first bobbin (30) being configured to engage with the first mating elements (35) of the adjacent second bobbin (30) to releasably secure the two bobbins (30) together, and the coil (40) being disposed between the base flange (31) of the first bobbin (30) and the base flange (31) of the adjacent second bobbin (30).

2. 2. The filter choke of claim 1, wherein each bobbin comprises two tubular sections extending perpendicularly from the base flange, each of the tubular sections including an opening for receiving a different one of the two core legs; a coil formed by a conductor having a plurality of windings is disposed around each tubular section of the bobbin; one of the at least two bobbins is configured such that each coil in a pre-wound state is attachable to an associated one of the two tubular sections; and when the filter choke is assembled, the coil is disposed between the base flanges of adjacent bobbins.

3. 3. A filter choke (10) according to claim 1 or 2, characterized in that each bobbin (30) comprises guide elements (43a-43f) arranged on the bottom surface (36a) and / or on the top surface (36b) of its base flange (31) for positioning and / or aligning at least one terminal (42a, 42b) of the coil (40) formed by the conductor (41).

4. 3. The filter choke (10) of claim 1 or 2, characterized in that the at least two first mating elements (35) each include a portion (38a) and / or a corresponding mating portion (38b) configured to form a snap fit (38) with the adjacent second bobbin (30).

5. 5. The filter choke (10) of claim 4, wherein for each first mating element (35), the snap-fit ​​portion (38a) and the snap-fit ​​mating portion (38b) extend in opposite axial directions from an edge (34) of the base flange (31).

6. 3. The filter choke (10) according to claim 1 or 2, characterized in that the base flange (31) of one of the at least two bobbins (30) comprises two second mating elements (39a) for releasably engaging with corresponding mating elements (39b) of a core clip (24) configured to secure at least one of the plurality of core segments (23) of the magnetic core (20).

7. 3. The filter choke (10) of claim 1 or 2, characterized in that a lid portion (37) made of an insulating material and having substantially the same shape as the base flange (31) of the bobbin (30) is removably fixed to the outer bobbin of the first bobbin (30) and the second bobbin (30).

8. The magnetic core (20) comprises a low reluctance bypass path (25) around a gap (26), the gap (26) having a gap surface normal oriented substantially parallel to the magnetic flux direction during operation of the filter choke (10). The bypass path (25) further comprises an overlap region (27) between two core segments (23) disposed adjacent to the gap (26), the overlap region (27) being such that the interface normal thereof is inclined to the gap (26) during operation of the filter choke (10).

3. A filter choke (10) according to claim 1 or 2, characterized in that it is oriented substantially perpendicular to the magnetic flux.

9. 3. A filter choke (10) according to claim 1 or 2, characterized in that the magnetic core (20) comprises at least four core segments (23) arranged in at least two layers, each layer including closed magnetic sub-cores (27 a, 27 b) having substantially the same geometric shape formed from at least two core segments (23), the sub-cores (27 a, 27 b) being coaxially aligned with one another.

10. The core segments (23) of the sub-cores (27a, 27b) in different layers are spaced apart by their gap plane normals.

10. A filter choke (10) according to claim 9, wherein the gaps (26) of the different sub-cores (27a, 27b) are arranged offset from one another, the gaps being oriented substantially parallel to the magnetic flux.

11. The filter choke (10) of claim 1 or 2, wherein the conductor (41) comprises a rectangular wire.

12. 3. The filter choke (10) of claim 1 or 2, wherein the plurality of core segments (23) comprise different core materials.

13. 3. The filter choke (10) of claim 1 or 2, wherein the at least two bobbins (30) are substantially identical to one another.

14. 3. An electrical device, in particular an inverter, comprising a filter choke (10) according to claim 1 or 2, said filter choke acting as a common mode choke within said electrical device.

15. A method for manufacturing a filter choke (10) according to claim 1 or 2, comprising the steps of: providing at least two core segments (23) configured to be assembled into a closed magnetic core (20) having two core legs (21, 22); providing a first bobbin (30) and a second bobbin (30), each of the bobbins (30) comprising a base flange (31) and a tubular section (32) extending perpendicularly from the base flange (31), the tubular section (32) comprising an opening (33) for receiving one of the two core legs (21, 22); Winding the conductor (41) to form at least two coils (40) by using an automatic winding process; placing a pre-wound coil (40) on the tubular section (32) of each bobbin (30); placing the first bobbin (30) one above the other on the second bobbin (30) and latching the first bobbin (30) to the second bobbin (30) so that their openings (33) are coaxially oriented, and terminals (42a, 42b) of the coil (40) are positioned substantially in place; inserting the core segments (23) into the openings (33) of the bobbin (30) to form a closed magnetic core (20); A method comprising:

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