EP2463869B2 - Inductive component with improved core properties - Google Patents

Description

The invention relates to an inductive component with a winding and a core.

Inductive components such as chokes, transformers and transmitters are widely used in electrical and electronic circuits. The electrical properties of the inductive components depend on their structure and the properties of the windings and the core.

The document DE 10212930 A1 shows an inductive component with a central slug and an outer sleeve. The latter has a permanent magnet section which is glued to another section.

The document US 2008/0055034 A1 shows a component with a core which has a part with a double-T-shaped cross-section and a sintered outer jacket which is separate therefrom and which surrounds the outside of the coil.

The document EP 1211700 A2 shows a component with a multi-part ferromagnetic core which also has a magnetic part.

The document US 4943793 A shows a component with a core in which the material properties of the center column, top and bottom differ from those of the side walls.

The document US 2006/0125586 A1 shows a core with a first part which is embedded in a second part, the material properties of the parts differing.

The document DE 3913558 A1 shows a multi-part ferrite core in which part cores with different material properties can be combined.

The document US 2011/0121935 A1 shows a core, the inner part of which has different magnetic properties from the outer part.

The document EP 1061140 A1 shows a cylinder with several regions of different magnetic properties.

The publication of Alex Van den Bossche, Vencislav Cekov Valchev: Inductors and Transformers for Power Electronics, page 318f (CRC Press Taylor & Francis Group, 2005, ISBN: 1-57444-679-7 ) discloses a core having a central leg made of a low-permeability material.

The document DE 10 2006 026 466 B3 shows a core in which an air gap comprises non-ferromagnetic layers and thin ferromagnetic material layers.

The post-published document WO 2011/131341 A1 discloses a core with different types of magnetic materials.

The desired inductive properties can be achieved, for example, by suitable selection or adaptation of the winding and / or the permeability. The permeability can be reduced by a large air gap, but this increases the leakage flux in the air gap and the associated losses. It is particularly important to improve the properties of the magnetic core.

To provide an alternative component, the invention relates to an inductive component with a core, comprising a central slug and on the end Outer core parts adjacent to the middle slug, and a winding which is arranged between the middle slug and the outer core parts. The core includes a plurality of core areas containing different magnetic materials, and the center slug includes areas containing different materials.

An inductive component is provided with a winding and a core which comprises a plurality of core regions which contain several different magnetic materials. With the term winding, the inductive component comprises a single-layer and multi-layer winding as well as one of several such windings on a core.

The different magnetic materials preferably have different magnetic properties. The term different magnetic materials is to be understood as meaning that it includes at least two different magnetic materials or that it is a material of a physical chemical composition with different magnetic material parameters in certain areas contains. The parameters can, for example, be optimized with regard to the operating conditions of the areas.

Such a magnetic core can in principle comprise any core shape, that is to say for example core shapes with the designations C, U, E, P, X, toroidal core and other core shapes or core shapes derived therefrom. However, the invention can be used particularly advantageously in the case of core molds which have a central column or a central slug. In this context, other core areas are to be understood as the legs and the yoke areas connecting them to the central section. Typically, the complete core is formed from two core halves, each of which includes legs, yokes and a central slug. Alternatively, the core can comprise a central slug and separate outer core parts. Other forms of separation are conceivable.

In the case of the core of the inductive component, the central slug itself contains different materials, or the central slug contains a different magnetic material than the other regions of the core, or the core is constructed from a combination of both alternatives.

In a preferred embodiment, the different materials can be layered, the layers of which are arranged one behind the other in an alternating sequence, for example in the axial direction of the central column. These layers can be disk-shaped and alternately contain a layer with high permeability and a layer with no or low permeability. Another preferred embodiment includes a central slug made of a magnetic material that is different from the magnetic material of the other core areas. Another preferred one Embodiment contains combinations of the two aforementioned embodiments. The mechanical connection of the central section with the other core areas is done by screwing. In the case of a screw connection, the central piece preferably has a central hole through which a plastic screw is inserted, which holds the core together. This is particularly useful when two core halves are placed against one another, because then one plastic screw simultaneously holds the two core halves together.

In transformers and chokes in particular, an air gap is an important functional component because it significantly reduces the magnetic flux density of the core and, for example, linearizes the magnetization characteristic so that magnetic saturation of the core material only occurs at higher field strengths. A significant part of the magnetic energy is stored in the air gap of storage chokes, which leads to disadvantages such as lower inductance or high forces. In the case of cores with a central bleed, the air gap is typically arranged between the two central bleeds of the core halves. The proposed inductive component makes it possible to distribute the air gap virtually over the length of the entire central section. The air gap distributed over several sections can be formed in the central slug by disks, for example made of ferrite material, separated by disks made of other material.

With the inductive component it is possible to improve disadvantageous properties of the magnetic core. This includes, in particular, a reduction in leakage flux and losses. This will make it possible to get through the losses prevent conditional higher temperatures and reduce the cost of a cooling system. At the same time, it becomes possible to improve the efficiency of the inductive component.

The structure and manufacture of a core for an inductive component are explained purely by way of example using the structure of a magnetic core with a central nozzle. Iron powder material or ferrite material, that is to say ferromagnetic materials advantageously with high saturation values, are particularly suitable as different magnetic materials for the core. Both materials have disadvantages and advantages which are known per se. An iron powder core, for example, has the disadvantage of brittleness, but the advantage of the high saturation value Bs of 1 Tesla (1 T) to 1.5 T, which can be achieved, for example, with an iron powder core. The individual powder grains, which are still separated from one another by a non-magnetic or low-magnetic layer, already cause the air gap to be distributed, which improves the induction of saturation and softens the saturation. In contrast, a standard ferrite material has a saturation value Bs of approximately 0.4 T and a steep saturation behavior.

The use of several different magnetic materials, for example in the middle section of a magnetic core, makes it possible to optimize the magnetic properties of the core. Thus, depending on the structure of the core, the resulting saturation value will be in the range between the saturation value of a ferrite material or a powder material, for example iron powder material. This means that the saturation value will be in the range between 0.4 T and 1.5 T.

wobei µ_tot die Gesamtpermeabilität, I_e,tot die gesamte effektive Länge des Magnetkreises, I_i die magnetische Länge eines i-ten Bereichs und µ_i die Permeabilität des i-ten Bereichs ist.The combination of a material with lower permeability for the central slug such as iron powder with an exemplary permeability of 10 to 50 and a ferrite material for the other areas with an exemplary permeability of 1000 to 3000 makes it possible to determine the total permeability as well as the total length of the air gap or the air gaps in the Reduced compared to a core consisting only of ferrite material. The total permeability is: $${\mu }_{\mathit{dead}}=\frac{{\mathrm{I.}}_{e,\mathit{dead}}}{\left(\frac{{\mathrm{I.}}_1}{{\mu }_1}+\frac{{\mathrm{I.}}_2}{{\mathrm{<figure-callout\; id="2"\; label="\mu "\; filenames="imgf0001.png,imgf0002.png"\; state="\{\{state\}\}">\mu </figure-callout>}}_2}+\frac{{\mathrm{I.}}_i}{{\mu }_i}+\cdots \right)},$$

where µ _{tot is} the total _{permeability, I e, tot is} the total effective length of the magnetic circuit, I _{i is} the magnetic length of an i-th area and µ _{i is} the permeability of the i-th area.

Due to the shorter overall length of the air gaps in the central vent, the lengths of the partial air gaps are also shorter, which reduces the leakage flux and the resulting losses.

The optimization of the magnetic core properties in turn makes it possible to reduce the dimensions of the core and, in particular, to reduce the cross-section or the diameter of the central slug and the winding applied to it, which in turn enables the volume of the winding to be reduced. This in turn makes it possible to reduce the overall dimensions of an inductive component and thus also to reduce the costs for the production of the inductive component. The reduction in the effective area of the central vent when using a material a higher saturation value is accompanied by an increase in the saturation value and is, for example, 0.4T / 1.5T when using a material with 1.5T compared to using a material with 0.4T. The reduction in the central stub diameter is also associated with a reduction in the external dimensions of the component, which allows smaller and more material-saving and thus more cost-effective housings to be used.

The effective length of the winding results from the number of turns and the length of the respective winding. In the case of a smaller inner diameter of the winding, which is possible due to the slimmer central slug, the total length of the wire of the winding is therefore reduced. This in turn causes a reduction in the material used for the winding, for example copper, so that resource-saving production and use of the inductive component is ensured. Therefore, not only the reduced costs for the magnetic core but also the lower costs for the winding contribute to reducing the costs and achieving advantages for the inductive component. On the other hand, the electrical properties of the inductive component are improved because the shorter overall length of the wire of the winding reduces the losses in the winding and increases the efficiency of the inductive component.

In the case of the inductive component, it is advantageous to shape the central slug with the aid of ferromagnetic powder material and the remaining parts of the core from ferrite material. Due to the high saturation value of the central bleed created in this way, the saturation behavior of the core is optimized overall and the magnetic flux through the central bleed can affect the adjacent parts of the core optimally distribute from ferrite material. In order to achieve an optimal transition of the flow from the central slug to the adjacent core parts, the central slug is adapted in its shape, for example by means of a central part with a small diameter, which increases in size towards the transition to the adjacent ferrite material in the foot area of the central slug. The diameter and the thickness of the transition part depend on the limit values of the magnetic saturation of the two ferromagnetic materials.

Such a transition part between the central slug and the adjoining other core parts is preferably made of the same material as the material in the central part of the central slug, that is to say, for example, of powder material. The transition part has the advantage that it acts like a flange and is able to guide the winding laterally. The transition part thus fulfills a flange function which is similar to the function of a flange of a winding support. This flange-like transition part can have the same outer diameter as the winding. With standard core shapes, for example a P or X core, a separate winding carrier is therefore not necessary. However, in the case of such a central slug with a flange function at the end, it is necessary to electrically isolate the central slug and the flange from the winding. For this purpose, the central section and the flange are coated with an insulating material of small thickness or the coil windings themselves are insulated. This insulating coating material on the elements of the central vent has little or no permeability and has the effect that the insulation forms partial air gaps on the end faces of the central vent. The coating of the central portion can be, for example, 0.2 mm thick, which is a common coating thickness. Through the Coating creates an air gap between the central slug and the other core parts.

In one embodiment, in which the central slug is formed from disks of different materials, it is provided that disk-shaped magnetic material, for example with ferromagnetic powder, is used and other disks made of material with little or no permeability are to be arranged between the disks made of this material. Such interposed disks made of material with little or no permeability are also suitable for compensating for the differences between the height of the central column or the central section and the outer core areas. A further function of such a disc-shaped material with no or little permeability in the central slug causes a distributed air gap. Furthermore, the total permeability can be reduced, the total length of the air gap can be reduced and the magnetic flux can be optimized.

In the event that the middle section consists of two parts, each formed from one piece, containing a magnetic material, the finished core, composed of two core halves, comprises as an air gap twice the insulating distance between the two central parts of the middle section and the respective distance between the outer part of the middle section and the adjoining core parts. Such an arrangement furthermore reduces the leakage flux compared to an arrangement with only one air gap. However, a reduction in the leakage flux also means a reduction in the losses. In an embodiment in which the permeability is reduced, the central bleed comprises two identical or symmetrical parts, between which a disc of material without permeability or is arranged with low permeability. The disc can compensate for differences, for example with regard to the fit, between the central slug and the outer areas. A further aspect is that the disk divides the entire air gap into three parts, namely two between the middle socket ends and the other core areas and one between the two middle socket parts, which reduces the leakage flux.

The provision of several air gaps, a central bleed made of material with low permeability, for example made of iron powder, or the combination of ferrite areas with iron powder areas as central bleed reduce the leakage flux or the losses. The provision of several air gaps in the central vent reduces the leakage flux, effort and costs for the cooling system and increases the performance of the component.

By constructing the magnetic core in which the central slug contains one material, for example a ferromagnetic powder, and the outer core part another material, for example ferrite material, it is possible to optimize the overall permeability of the core. This is possible because ferromagnetic powder, for example iron powder, has a permeability between 10 and 50, while ferrite material has a permeability in the range from 1000 to 3000. By using a different material for the core, for example in the central slug, it is therefore possible to reduce the overall permeability of the magnetic core arrangement compared to a pure ferrite core. At the same time, such an arrangement makes it possible to distribute the entire effective air gap and thus to reduce the leakage flux and the losses caused by it.

An inductive component with a magnetic core as proposed also has the advantage that the temperature behavior of the entire core arrangement can be improved. Ferrite material, for example, has a temperature dependency with several loss maxima. The overall temperature dependency of the proposed core arrangement can be improved both through the possibility of variation in the manufacture, e.g. during pressing and sintering, of the ferrite material and through the combination with another ferromagnetic material, e.g. powder material. The permeability can depend on the temperature. Ferrite materials can, for example, have two tips that can be shifted by varying the manufacturing process. The optimization can be directed both to the middle section and to the other core areas, wherein the target specifications of the optimization, for example saturation value, loss or permeability, can differ for the various core areas. The optimization can reduce the overall permeability, the size of the air gap and the leakage flux. Such an optimization is not possible in the case of cores which only consist of the same material.

The central slug can be constructed in different embodiments and, for example, contain disks of different material and / or a uniform material that differs from the external core part. Furthermore, the central piece can comprise parts which are integrally formed in the shape of a flange at the end. It is advantageous to provide a central bore for the individual parts of the central port so that they are aligned with a correspondingly aligned bore in the external core parts can be connected by a screw. Such a screw is in particular made of insulating material and makes it possible to further optimize the overall permeability of the magnetic circuit of the inductive component. This is possible, for example, by adjusting the pressure exerted by the screw on the central hole and thus on the different core elements of the central port and the outer core areas. A change in the pressure exerted by the screw causes a change in the remaining air gap. In particular, when the central slug also includes panes with little or no permeability, it is possible to choose this material in such a way that it is mechanically flexible. In particular, plastic and silicone come into question as materials, so that the pressure exerted by the screw results in a quasi-resilient function. The pressure exerted by the screw on the core parts can be adjusted with a torque wrench, for example.

In the event that the center column contains ferrite or ferrite disks, these can be manufactured in such a way that the minimum of the losses occurs at higher temperatures than in the case of the different ferrite material of the outer core part. Therefore, in this case the temperatures of the central vent can be higher than the temperatures of the outer core part. This provides better cooling conditions for the core arrangement, since the central section can only be cooled by conduction, while the entire core arrangement can also be cooled by convection or fan cooling. On the other hand, such ferrite disks of the middle section can also be made with a material with a higher saturation Bs than the outer core parts. The adaptation of the ferrite materials of the core areas to their operating temperatures in order to reduce the losses, can be done by adjusting the pressure, temperature and sintering profile when sintering the areas. Such a variation of the manufacturing process for different core areas is not possible with a one-piece core. Another approach is to use low permeability material, such as iron powder, for the manufacture of the central slug, which reduces the diameter in order to reduce the effective winding length, the volume of the material for the winding and ultimately the losses. The combination of the different materials, the reduced dimensions and the shorter conductor length optimizes the losses in terms of the magnetic material and the windings compared to a component with a one-piece core, which also increases efficiency and reduces costs.

Optimization with regard to the saturation value can be achieved by using different magnetic materials for the different core parts. For example, the ferrite disks in the central slug can be made of a material with a higher saturation value, adapted to the operating temperature. The operating temperature of the central port is higher than that of the outer core areas; the former is, for example, in the region of 100 degrees Celsius, the latter in the region of 80 degrees Celsius. With ferrite material, the saturation value increases with decreasing temperature. For example, the saturation value increases with a temperature drop between the central nozzle and the outer core area by approximately 20mT for a conventional ferrite material.

Embodiments of the invention emerge from the figures of the drawing. The same functional elements are represented by the same reference symbols.

Figur 1

eine Drossel mit scheibenförmig aufgebauten Mittelbutzen und verteiltem Luftspalt bei einem P-Kern,

Figur 2

eine Drossel mit X-Kern und scheibenförmig aufgebautem Mittelbutzen mit verteiltem Luftspalt,

Figur 3

eine Drossel mit einer Mittelsäule und einem endseitig angeordneten Flansch,

Figur 4

eine Drossel mit einer Mittelsäule mit endseitigem Flansch und der Funktion eines Wicklungsträgers und

Figur 5

ein Detail des Verlaufs der magnetischen Flussdichte im Übergangsbereich von dem Mittelbutzen mit endseitigem Flansch zu externen Kernbereichen.

Show it:

Figure 1

a throttle with a disc-shaped central nozzle and a distributed air gap with a P-core,

Figure 2

a throttle with an X-core and a disc-shaped central nozzle with a distributed air gap,

Figure 3

a throttle with a central column and a flange arranged at the end,

Figure 4

a choke with a central column with a flange at the end and the function of a winding support and

Figure 5

a detail of the course of the magnetic flux density in the transition area from the central slug with the flange at the end to the external core areas.

Although the exemplary embodiments show cross sections of chokes, it goes without saying that, instead of chokes, transformers or transmitters can also have a corresponding structure. Different core shapes can also be provided, for example with a P or X shape or as pot or bowl cores. In this context, an X core is understood to be a core shape which, adjoining the central neck, comprises at least four radially diverging yoke regions, on each of which a leg is attached in the direction of the central neck. P and X cores have a compact shape with little interference.

According to the cross section of the Figure 1 A P-core is made up of two core parts 1a and 1b placed against one another, which can comprise ferrite material. A slug is arranged in the center of the core and is constructed in the form of a disk from different materials. Thus, the central slug contains disks 2 which contain either ferromagnetic powder or a ferrite material that is different from the ferrite material of the outer core part 1a, 1b. A material 3 with little or no permeability is arranged between the panes 2. Alternatively, these are disks made of the material 3 mentioned, advantageously flexible, or the ferromagnetic disks 2 are insulated with an insulating coating. The winding 5 is arranged between the central slug and the outer core parts. The entire arrangement of the inductive component is held together by a screw 4 in a through hole 6, which connects the outer core parts and the central flap with one another. The air gap, which is distributed over the areas with little or no permeability between the ferromagnetic disks and the outer core area, is set and adjusted by the pressure exerted by the pressing force of the screw on the outer core part and the central section.

Figure 2 Figure 11 shows a throttle arrangement using an X-core. The arrangement shows two outer core halves 1a and b, which can comprise ferrite material, as well as ferromagnetic disks 2 of the middle section, which are separated from one another by a material 3 with little or no permeability or, alternatively, by an insulating coating. The winding 5 of the choke is arranged between the layer structure of the central slug and the outer core parts 1a and 1b, respectively. All parts of the core are tightened by a 4 in a through hole 6 held together and guided, with which the pressing force on the elements of the magnetic core can be adjusted. In this exemplary embodiment, too, there is a spatially distributed air gap.

Figure 3 shows a reactor with a P or an X core, in which the external halves 1a and 1b contain ferrite. The central middle section contains two parts 2 which contain a flange 7 at the end of the external core areas. The center slug can comprise iron powder. The flange 7 has the effect that, on the one hand, the magnetic flux from the central slug to the outer core parts is better distributed and, on the other hand, that the winding 5 is at least partially guided.

The insulation of the winding 5 with respect to the core 1a and 1b is designed in particular as an insulated winding or as an insulating coating of the central slug. In the latter case, it is possible to apply the winding directly in the intermediate area between the central slug and the external core parts. At the same time, the insulation coating of the central bleed fulfills the task of distributing the air gap of the throttle over the central area between the central bleed halves and the two outer flange areas. This results in improved loss conditions for the throttle, so that overall a throttle with a smaller design and at the same time improved properties compared to conventional throttles is achieved. In one embodiment, a disk made of flexible material (in Figure 3 not shown), the permeability of which is low or zero. Due to the flexibility of the disk, it acts as a spring. The screw allows flexibility Using the disc, the distance between the parts 2 of the central stub can be varied.

According to Figure 4 an arrangement with a P or X core shape is shown which differs from the Figure 3 differs in that the flange-shaped areas 7, which are arranged at the end between the central boss parts 2 and the external core parts 1a and 1b, extend from the central bore 6 with the guide screw 4 to the external core parts. This makes it possible to arrange the winding 5 completely in the area formed by the flanges and thus also to dispense with a separate winding carrier for the winding. The stepped enlarged diameter of the central port 2 act as a transition area for distributing the flux and for holding the winding 5. Together, the central part of the central port 2 and the steps give the shape of the winding 5.

Figure 5 shows schematically the transition of the magnetic flux from the central nozzle 2 via the flange arranged at the end of this central nozzle 2 to the external core parts. As shown purely schematically on the basis of the arrows 8, the very large magnetic flux in the central slug 2 is already reduced and distributed in the transition area of the flange 7, so that an adaptation to the flux present in the outer ferrite part 1 of the core is ensured. In one embodiment, the central slug 2 comprises iron powder; the other parts of the core comprise ferrite material. The transition area optimizes the flow transition between the parts, in which it is necessary to distribute the flow from the central nozzle 2 with a higher saturation value due to the iron powder to the ferrite material with a lower saturation value. The thickness and diameter of the Transition areas depend on the ratio of the saturation values in the middle section 2 and the other core parts.

Claims (12)

1. Inductive component comprising a core, comprising a center leg (2) and outer core parts (la, 1b) adjoining the center leg (2) at the ends, and a winding (5), which is arranged between the center leg (2) and the outer core parts (la, 1b),
   wherein the core comprises a plurality of core areas (1, 2) which contain different magnetic materials, and the center leg (2) contains areas with different materials, wherein, in the case of the center leg (2), a layer sequence of different materials is screwed to one another.
2. Inductive component according to Claim 1,
   wherein the different magnetic materials have different magnetic characteristics.
3. Inductive component according to Claim 1 or 2,
   wherein the different magnetic materials comprise a material type with different magnetic parameters.
4. Inductive component according to one of Claims 1 to 3, whose magnetic core characteristics are different to the magnetic core characteristics which are associated with each individual one of the different magnetic materials.
5. Inductive component according to one of Claims 1 to 4,
   wherein the different magnetic materials of the center leg are in the form of a sequence of layers.
6. Inductive component according to one of Claims 1 to 5,
   wherein the center leg (2) is composed of a magnetic material which differs from a magnetic material of the outer core areas.
7. Inductive component according to Claim 6,
   wherein the center leg (2) contains a ferromagnetic powder, and the outer core areas contain ferrite.
8. Inductive component according to Claim 6 or 7,
   wherein the center leg (2) contains a plurality of layers which are in the form of disks and are composed of magnetic material.
9. Inductive component according to one of Claims 6 to 8,
   wherein the magnetic materials of the center leg (2), which are in the form of disks, are provided with an insulating coating (3).
10. Inductive component according to one of Claims 1 to 8,
    wherein a flexible material (3) of low or zero permeability is arranged between areas of material with higher permeability (2) .
11. Inductive component according to one of the preceding claims,
    wherein the center leg (2) has two parts, the center leg having two parts (2) composed of material with higher permeability, between which a disk composed of flexible material with low or zero permeability is arranged.
12. Inductive component according to one of Claims 6 to 11,
    wherein the center leg has a formed-out area (7) in the form of a flange at the end facing the outer core areas.

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