DE102013112325B4 - Toroidal coil and manufacturing process for a toroidal coil - Google Patents

Abstract

Ring coil with at least one conductor which runs helically around an annular core region (2) and which has a rectangular outer shape with longitudinal side surfaces (12, 14) and narrower transverse side surfaces (13, 15) relative to these, the conductor being a waveguide (1 ), which is twisted in such a way that on the inside of the core area (2) the narrower transverse side surfaces (13, 15) and on the outside of the core area (2) the longitudinal side surfaces (12, 14) of the waveguide (1) on the core area ( 2) apply.

Description

The invention relates to a toroidal coil with at least one conductor which runs helically around an annular core area and has a rectangular outer shape with longitudinal side surfaces and narrower transverse side surfaces relative to these. The invention further relates to a manufacturing method for such a toroidal coil.

Coils are used in a variety of ways in power electronics, particularly as choke coils. In inverters, for example, which are used to convert direct current into alternating current suitable for feeding into a power supply network, choke coils are used as energy buffers in DC-DC converters and as part of filters on the output side.

In order to achieve the inductance values required for energy storage, chokes with a core made of a highly permeable material, for example iron or ferrite, have so far been preferred. With the use of increasingly higher clock frequencies of power semiconductors in the inverters, the highly permeable core material can increasingly be dispensed with in the choke coils and the choke coils can be designed as so-called air coils. To minimize any magnetic stray fields, ring coils, also known as toroidal coils, are preferably used. In a toroidal coil, at least one conductor is wound helically around an annular core area. The annular core region can, for example, have the shape of a torus, in which the ring is as circular as the cross section of the core when the ring is cut in a direction radial with respect to the ring.

A toroidal coil with a conductor that has a rectangular cross section is, for example, from the publication EP 2 197 006 A1 known. The rectangular conductor has narrow transverse sides in profile and longer longitudinal sides. The conductor is wound on a toroidal core in such a way that one of its narrower transverse sides faces the surface of the toroidal core.

A disadvantage of toroidal coils compared to coils with a straight core, so-called bar coils, is that there is less winding space available for the conductors in the inner area of the toroidal coil than in the outer area of the coil, where the core has a larger circumference than in the inner area .

In order to make the best possible use of the available changing space, it is from the publication US 4,665,952 A a toroidal core transformer is known in which one of the coils is designed as a toroidal coil with a conductor which consists of two conductors placed one on top of the other, each with a square cross section. In the inner area of the toroidal coil, the two partial conductors lie one behind the other in the radial direction from the center of the toroidal coil outwards, whereas in the outer area they run next to one another. In order to create such a coil, the publication describes a winding machine which is able to twist the two partial conductors around each other when winding the coil. The winding machine is correspondingly mechanically complex and the manufacturing process is limited to sufficiently large conductor cross sections and radii of the core due to the complexity of the winding machine.

From the publication DE 197 33 616 A1 A toroidal core coil is known in which a conductor with an initially circular profile is crushed in sections during winding so that it is flattened in the inner region of the toroidal core in the radial direction of the toroidal core. The publication US 7,154,368 B2 describes a comparable toroidal core coil in which a conductor is preformed so that its profile changes between a circular profile and a wedge-shaped profile, with sections with the circular profile positioned on the outside of the toroidal core and sections with the wedge-shaped profile on the inside of the toroidal core are. In both cases, a higher winding density of the toroidal core coil is achieved. The methods mentioned require a complex winding technique in order to either deform the conductor during winding or to position the differently pre-shaped sections of the conductor accordingly during winding.

As the frequency increases, the penetration depth of electrical currents in a conductor material used also decreases. Effectively, only a portion of the conductor material used contributes to the power line. In this case, the use of solid ladders (solid ladders) leads to an unnecessarily high use of materials, which is associated with increased weight and additional costs. In addition, losses due to eddy currents increase when using solid conductors. Alternatively, it is known to use a bundle of conductor strands that are insulated from each other instead of a solid conductor, whereby the losses caused by eddy currents can be reduced. However, when using a stranded conductor bundle, additional difficulties arise in the processing of the conductors, in particular due to the insulation layers that insulate the individual strands from one another, which lead to problems when contacting the stranded conductors on circuit boards. In addition, the conductor strands are not dimensionally stable, which makes it difficult to create an air coil.

From the publication DE 20 2011 003 256 U1 It is known to use a waveguide as the conductor of a toroidal core coil, through which a cooling medium flows in order to achieve cooling of the conductor with high cooling performance.

It is an object of the present invention to create a toroidal coil that is suitable for high frequencies, has low eddy currents and low stray electromagnetic fields and has a low ohmic resistance at high frequencies with regard to the conductor material used. In addition, a low space consumption, i.e. a high volume-specific inductance, should be achieved. It is a further object to provide a method for producing air coils with complex geometries, with which the aforementioned air coils can be created.

This task is solved by a toroidal coil and a method for producing a toroidal coil with the respective features of the independent claims. Advantageous refinements and further developments are the subject of the dependent claims.

A toroidal coil according to the invention of the type mentioned at the outset is characterized in that the conductor is a waveguide which is twisted in such a way that the narrower transverse side surfaces of the waveguide rest on the inside of the core region and the longitudinal side surfaces of the waveguide rest on the core region on the outside of the core region. The torsion ensures that the conductor has a first cross-sectional area on an outside of the core area and a second cross-sectional area on an inside of the core area, the first and second cross-sectional areas differing with regard to their orientation tangential to the core area. Both in the inner and outer areas of the toroidal coil, the individual turns of the waveguide can lie close to one another, which minimizes stray fields.

By designing the conductor as a waveguide, the shallow penetration depth of the current at high frequencies is taken into account. The conductor material used for the coil is effectively used for power conduction at high frequencies, saving material and weight. Due to the different properties of the cross-sectional area of the waveguide in the inside and outside of the coil, the waveguide can be optimally adapted to the shape of the core area, which means that the available winding space can be used particularly well. The cross-sectional areas can differ from each other in various respects: in terms of their shape, their surface area or, if the shape is fundamentally the same, in their orientation in space relative to the core area.

The annular core area can extend along a circle, an ellipse or an oval. The core can also have a round, oval or elliptical cross section, for example, in a direction perpendicular to its extension.

The toroidal coil can be designed as an air coil, i.e. not have an actual core made of a magnetically active material. Alternatively, an annular core can be provided which completely or partially fills the core area. A core material with a high magnetic permeability is preferably used.

In a further advantageous embodiment of the toroidal coil, the ratio of the widths of the longitudinal side surfaces to the transverse side surfaces is adapted to the ratio of an outer to an inner diameter of the core region. In this way, the changing room can be filled as best as possible.

In any case, the shape or dimensioning of the waveguide can be varied in such a way that it has a constant material cross-sectional area along its length. This is achieved by the waveguide having a constant current-carrying capacity and a constant resistance per unit length along its longitudinal extent.
In a further advantageous embodiment of the toroidal coil, a further conductor runs in the at least one waveguide. The further conductor is preferably also a waveguide. The principle of a conductor in a waveguide can be continued recursively, for example by nesting several waveguides concentrically one inside the other. The changing room can be used even better. It goes without saying that several conductors can also run in the at least one waveguide. Depending on the connection of the conductor or waveguides to one another and to the at least one comprehensive waveguide, a wide variety of electrical properties of the toroidal coil can be achieved, for example a further increased inductance by connecting the conductors in parallel or series, a transformative effect through separate operation of the conductors or even a dynamic adjustability of the inductance by specifically feeding compensation currents into at least one of the conductors when using another of the conductors as a working winding.

In a method according to the invention for producing a toroidal coil with at least one waveguide wound helically around a toroidal core region, which is twisted in such a way that the narrower transverse side surfaces of the waveguide rest against the core region on the inside of the core region and the long side surfaces of the waveguide rest on the outside of the core region at least one waveguide in a generative manufacturing process, in particular constructed additively.

A suitable generative manufacturing process is, for example, a laser sintering or laser melting process, in which the conductor is constructed from a powder, in particular a metal powder. The construction is preferably carried out in layers, but particularly preferably not in the direction of the longitudinal extent of the conductor, but in layers with regard to the toroidal coil.

The generative manufacturing process enables the production of toroidal coils with conductor geometries that cannot be produced using conventional processes or can only be produced with great effort. These include, in particular, toroidal coils in which the conductor is a waveguide and/or has cross-sections that vary along its longitudinal extent. The method according to the invention is therefore particularly suitable for producing one of the toroidal coils according to the invention described above.

In an advantageous embodiment of the method, spacer elements made of a preferably electrically insulating material are also introduced between different sections of the conductor. The spacer elements are preferably constructed additively. For example, ceramic materials can be constructed using the same manufacturing process as the conductor. Alternatively, plastics in particular can be used for the spacer elements, which can be constructed using a 3-dimensional printing process. In this way, electrically insulating spacer elements can be introduced between individual turns of the waveguide, through which the distance between the individual turns from one another can be further reduced. Spacer elements can also be incorporated into a waveguide, which serve to fix and electrically insulate other conductors that are inserted into the waveguide. In principle, the spacer elements can also be constructed from the same electrically conductive material as the conductor, provided that the spacer elements are dimensioned so small compared to the dimensions of the conductor that their overall influence on the electromagnetic properties of the toroidal coil is negligible.

• 1 eine isometrische Ansicht einer Ringspule in einem ersten Ausführungsbeispiel;
• 2 eine isometrische Schnittansicht der Spule aus 1;
• 3 eine isometrische Ansicht einer isoliert dargestellten Windung der Spule aus 1 und
• 4 eine isometrische Ansicht auf eine Querschnittsfläche eines Hohlleiters einer Ringspule in einem zweiten Ausführungsbeispiel.

The invention is explained in more detail below using exemplary embodiments with the aid of figures. The figures show:

• 1 an isometric view of a toroidal coil in a first exemplary embodiment;
• 2 an isometric sectional view of the coil 1 ;
• 3 an isometric view of an isolated winding of the coil 1 and
• 4 an isometric view of a cross-sectional area of a waveguide of a toroidal coil in a second exemplary embodiment.

1 shows a toroidal coil in an isometric view in a first exemplary embodiment. The coil has a waveguide 1 which runs helically around an annular core region 2. In the exemplary embodiment shown, the annular core region 2 is a torus, i.e. a body that is created by the rotation of a circular cross-sectional area of the core region about an axis that lies outside the cross-sectional area of the core region. As a result, the annular core area has the shape of a rod bent into a circular ring with a circular base area.

Within the scope of the application, instead of a circular core area, a core area can also be formed which has the shape of an ellipse or an oval or a body of any other shape that surrounds a central opening. In a radial direction, i.e. a direction that extends radially outward from the center of the central opening, the annular core region can also have a cross-sectional area other than that of a circle as in the case in 1 illustrated embodiment. In addition to a circular cross section, an oval or elliptical cross section is also preferred here. In principle, other cross sections are also possible, for example in the form of a polygon. However, since the waveguide follows the shape of the core area, a round core area with a constantly changing cross-section is more favorable than a square one.

At the in 1 In the ring coil shown, the waveguide 1 runs in 18 turns around the core area 2. A beginning and an end of the waveguide 1 meet directly in one of the turns. At the beginning or at the end of the waveguide 1, it merges into a connection 3 that projects vertically outwards and is each provided with mounting and/or contact means 4. In the example shown, the mounting and/or contact means 4 are formed by a recess in the connection 3. The toroidal coil is therefore for a screw Suitable for assembly and screw connection. Alternatively and/or additionally, soldering pins, soldering surfaces or even plug-in contacts can be provided for PCB assembly.

The waveguide 1 used has an outer rectangular cross-section and is twisted in such a way that in the outer region its longitudinal side surface rests tangentially on the annular core region 2 and in the inner region, towards the central opening of the toroidal coil, it rests tangentially on the core region 2 with a transverse side surface that is narrower than the longitudinal side surface applied.

The torsion of the waveguide 1 is based on 2 more clearly visible. 2 shows the toroidal coil 1 in an isometric sectional view, the section being carried out in the lateral plane of symmetry of the annular core area. The core area 2 is in the 2 represented by its surrounding circular center line. The center line of the core area 2 shown indicates the trajectory of the center of the circle, which forms the annular core area 2 as it rotates about the central axis.

In the sectional view of the 2 A first cross-sectional area 10 can be seen in the outer area and a second cross-sectional area 11 of the waveguide 1 in the inner area. Both cross-sectional surfaces 10, 11 are frame-shaped, formed by the longitudinal side surfaces 12 and 14 of the waveguide 1 and opposite the narrower transverse side surfaces 13 and 15. The longitudinal and transverse side surfaces 12 to 15 have the same wall thickness 16.

In the course of each one in the 2 In the half turn sections shown, the waveguide 1 is wound (twisted) by approximately 90°. As a result, in the outer area of the toroidal coil, the wider longitudinal side surface 12, 14 runs tangentially to the core area, whereas the transverse side surface 13, 15 runs essentially radially outwards. In the inner region of the toroidal coil, however, the longitudinal side surfaces 12, 14 run essentially radially, whereas the transverse side surfaces 13, 15 run tangentially to the core region. Both in the inner and outer areas of the toroidal coil, the individual turns of the waveguide 1 are closely adjacent to one another, which minimizes stray fields.

3 also shows another turn of the waveguide 1 of the toroidal coil in an isometric view 1 and 2 shown isolated from the other turns. Here too, the torsion of a total of 180° in one turn of the waveguide 1 can be clearly seen. Alternatively, the torsion of the upper and lower half winding sections by 90° can also be carried out in opposite directions, so that a total rotation of 0° per winding section results for a winding section.

In a further development of the toroidal coil shown, provision can be made for a coolant to be guided through the waveguide. For this purpose, corresponding coolant connections can be provided in the area of the connections 3 of the toroidal coil. Air or another gas or even a cooling liquid, for example deionized water, can be used as the coolant.

4 shows another embodiment of a toroidal coil. In 4 is again in a similar way as in 3 Only one turn of the toroidal coil is shown. In the overall structure, the toroidal coil is the 4 similar to that in the 1 and 2 reproduced trained.

In this exemplary embodiment, too, the waveguide 1 is rectangular with respect to its outer and inner cross-section, so that a substantially frame-shaped cross-sectional area results. Additional conductors 5, here three additional conductors 5, are guided through the interior of the waveguide 1. These additional conductors 5 can be as in the 4 shown, be solid conductors (solid conductors). However, it is also conceivable that the further conductors 5 are also designed as waveguides, for example designed as a tube with an outer and an inner circular cross section. Further conductors can then be arranged in the further conductors, for example also waveguides, which run concentrically in the further conductors.

The further conductors 5 can be connected in parallel and positioned and fixed within the waveguide 1 in an electrically insulated manner from one another by an insulating means that is not visible here. The other conductors 5 can be individually led out of the toroidal coil and connected externally. It is also conceivable that the further conductors 5 are already connected to one another and/or to the waveguide 1 within the toroidal coil, for example connected in parallel or connected in series or partly connected in parallel and partly in series. Wiring options are also conceivable in which the waveguide 1 serves as a shield for the other conductors 5.

With those in the 1 until 4 Ring coils shown, the waveguide 1 has an outer rectangular and an inner rectangular cross section. Alternatively, a toroidal coil can also have a waveguide that has a circular diameter inside and outside.

With those in the 1 until 4 In the exemplary embodiments shown, the orientation of the cross-sectional area changes along the waveguide, but without changing the basic shape of the cross-sectional area. The wall thickness also does not change along the waveguide. In the case of a ring coil, however, it can also be provided that the outer and/or inner shape of the cross-sectional area changes along the waveguide 1, for example in such a way that the first, external cross-sectional area of the waveguide is rectangular and the second, located in the inner region of the ring coil Cross-sectional area of the waveguide is trapezoidal. The two basic shapes, rectangular and trapezoidal, then continuously merge into one another as the waveguide moves from the outside to the inside. The change between these basic shapes takes place periodically, just like the orientation of the rectangular cross-sectional area in the exemplary embodiment 1 until 4 changed periodically and continuously by the torsion of the waveguide 1.

In a further toroidal coil not according to the invention, it is possible for both the first and second cross-sectional areas to be circular, with the first cross-sectional area located in the outer region of the toroidal coil having a larger outer diameter than the second cross-sectional area located in the inner area of the coil . However, the wall thickness of the waveguide changes periodically in such a way that the waveguide has a larger wall thickness with a smaller outer diameter than with a larger outer diameter. The interaction between outer diameter and wall thickness can take place in such a way that the waveguide has the same material cross-sectional area at every point along its length. The area available for the power line is therefore the same size along the entire waveguide.

In principle, one of the ring coils described above can be produced using a conventional winding technology. The waveguide can be pressurized with a liquid or gaseous medium in order to prevent the waveguide from collapsing during the winding process. Alternatively, it is also conceivable to introduce a granular or solid medium, for example a hardening plastic, into the waveguide for this purpose. An introduced solid or substance that has hardened after introduction can be removed again after the winding process by changing the temperature and/or a chemical solvent.

As the complexity of the winding geometry increases, especially when the cross section of the waveguide changes periodically and under certain circumstances takes on fundamentally different shapes, conventional production, in which the conductor is created beforehand and then wound into a coil in a winding process, is no longer possible.

According to the invention, a manufacturing method for a toroidal coil according to the invention with an optionally complex geometry provides for the coil to be manufactured in a generative manufacturing process, in particular in an additive manufacturing process. A generative manufacturing process is seen as a process in which an object is not created through mechanical forming, but rather is built up in the desired shape, usually layer by layer. Generative manufacturing processes are used, for example, in the area of “rapid prototyping”.

To create a toroidal coil in such a generative manufacturing process, the coil is built up layer by layer, preferably not along the longitudinal extent of the conductor, but layer by layer in a plane that is parallel to the lateral extension plane of the core-shaped region of the toroidal coil.

For example, a laser sintering process (e.g. Direct Metal Sintering - DMLS or Selective Laser Sintering - SLS) or a laser melting process (Selective Laser Melting - SLM) can be used as a suitable additive process. In these processes, the conductor and, if necessary, connections of the toroidal coil, a core or other conductors are built up layer by layer from a metal powder. For this purpose, the powder is applied over a large area, for example using a squeegee method, and then locally connected to the underlying, already built-up layer by applying local heat using a laser beam at the points where the conductor, a connection or another conductor is to be formed. Conductors, including waveguides, with any cross-sections, including continuously changing cross-sections, can be constructed in this way. Ring coils with waveguides running into one another can also be manufactured.

Other suitable generative manufacturing processes include selective melting using an electron beam (Selective Electron Beam Melting - SEBM) or laser deposition welding.

The process for constructing the waveguide, for example the laser sintering or laser melting process, can be combined with a process for depositing non-conductive elements, in particular plastics, in layers, for example a three-dimensional printing process, in order to be inserted into the toroidal coil between the individual turns of the Waveguide electrically insulated to introduce spacer elements. In the same way, spacer elements can be incorporated into the waveguide, which serve to fix and electrically insulate other conductors that are inserted into the waveguide.

A core that completely or partially fills the core region can also be manufactured in the waveguide and/or the connections and, if necessary, other conductors running in the waveguide in a generative manufacturing process. When the toroidal coil is manufactured, the core “grows” with the waveguide that later surrounds it.

During production in a generative process, openings can be specifically incorporated into the waveguide 1 in order to be able to more easily remove metal powder from which the waveguide 1 is formed that is not sintered or melted during the production process from the waveguide. The openings in the walls of the waveguide can also serve for better cooling through an air flow.

It goes without saying that the ring coils according to the application can also be constructed in the form of a transformer in which several conductors are wound around a common core area.

Reference symbol list

1

Waveguide

2

Core area

3

Connection

4

Assembly and/or contact means

5

another leader

10

first cross section

11

second cross section

12, 14

Long side surfaces

13, 15

Transverse side surfaces

16

wall

Claims (13)

Ring coil with at least one conductor which runs helically around an annular core region (2) and which has a rectangular outer shape with longitudinal side surfaces (12, 14) and narrower transverse side surfaces (13, 15) relative to these, the conductor being a waveguide (1 ), which is twisted in such a way that on the inside of the core area (2) the narrower transverse side surfaces (13, 15) and on the outside of the core area (2) the longitudinal side surfaces (12, 14) of the waveguide (1) on the core area ( 2) apply. toroidal coil Claim 1 , in which the annular core area (2) extends along a circle, an ellipse or an oval. toroidal coil Claim 1 or 2 , in which the core region (2) has a round, oval or elliptical cross section in a direction perpendicular to its extension. Toroidal coil according to one of the Claims 1 until 3 , in which the annular core area (2) is completely or partially filled with an annular core. Toroidal coil according to one of the Claims 1 until 4 , in which the ratio of the widths of the longitudinal side surfaces (12, 14) to the transverse side surfaces (13, 15) is adapted to the ratio of an outer to an inner diameter of the core area (2). Toroidal coil according to one of the Claims 1 until 5 , in which the waveguide (1) has a constant material cross-sectional area along its length. Toroidal coil according to one of the Claims 1 until 6 , in which a further conductor (5) runs in the at least one waveguide (1). toroidal coil Claim 7 , in which the further conductor (5) is a waveguide. Method for producing a toroidal coil with at least one waveguide (1) wound helically around a toroidal core region (2), which is twisted in such a way that the narrower transverse side surfaces (13, 15) are on the inside of the core region (2) and on the outside of the core region (2) the longitudinal side surfaces (12, 14) of the waveguide (1) rest on the core region (2), the at least one waveguide (1) being constructed in a generative manufacturing process, in particular additively. Procedure according to Claim 9 , in which the toroidal coil is built up in layers. Procedure according to Claim 9 or 10 , in which the at least one conductor is constructed from a powder, in particular a metal powder, in a laser sintering or laser melting process. Procedure according to one of the Claims 9 until 11 , in which spacer elements made of a preferably electrically insulating material are inserted between different sections of the conductor. Procedure according to Claim 12 , in which the spacer elements are also constructed additively, especially in a 3-dimensional printing process.

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