Coaxial transformer and method for producing a coaxial transformer

Abstract

The invention relates to a coaxial transformer (17) having: a coaxial cable (1) which forms a primary winding (19) and has an inner conductor (3) and a conductive cable shield (7); a secondary conductor (21) which forms a secondary winding (23); at least one magnetic core (25); and an earthing connection (11) which is connectable to a reference potential, wherein the primary and the secondary winding (19, 23) are each arranged in relation to the magnetic core (25), and the earthing connection (11) is electrically connected to the cable shield (7) such that the inner conductor (3) can be shielded by the cable shield (7). The invention also relates to a method (100) for producing a coaxial transformer (17).

Description

[0001] Coaxial transformer and method for manufacturing a coaxial transformer

[0002] The present invention relates to a coaxial transformer and a method for manufacturing a coaxial transformer.

[0003] Coaxial transformers are known from the prior art, which comprise a coaxial cable serving as the winding for the transformer. The coaxial cable has an inner conductor and an outer conductor in the form of a conductive cable shield. In known coaxial transformers, the coaxial cable is wound around the magnetic transformer core, with the inner conductor constituting the primary winding and the outer conductor constituting the secondary winding. This makes it possible to reach the primary and secondary windings of the transformer by winding the coaxial cable.

[0004] Coaxial transformers are used, among other things, for medium- and low-voltage DC systems, particularly for large photovoltaic (PV) systems, wind turbines, battery systems, electrolysis plants, and fuel cells. Coaxial transformers are also frequently used in power electronic converters with a medium-voltage connection to the AC grid, such as PV systems combined with battery systems and charging stations for electric vehicles, trucks, and buses. The use of DC transformers that rely on medium-frequency transformers (MFTs) for galvanic isolation is becoming increasingly important in these applications.

[0005] The transformers in these systems, especially MFTs, are typically operated at switching frequencies in the tens to three-digit kHz range and must, in particular, meet the requirements of voltages up to 60 kV (in medium-voltage applications) and / or up to 35 kV (in power electronic converters). These voltage ranges generally place high demands on electrical insulation, comparable to conventional transformers. The compact size of these transformers particularly increases the technical challenge of dielectric strength. In most applications, the primary and secondary currents are approximately equal, indicating that one of the main functions of MFTs is galvanic isolation. The voltages are transformed by the converter circuitry, with the transformation ratio of the MFTs typically close to 1 or in the single-digit range.

[0006] A major problem with the traditional design of coaxial transformers is the challenge of ensuring effective electrical insulation and shielding between the inner and outer conductors. The proximity of these two conductors, which have different electrical potentials, increases the risk of electrical flashovers and interference. Inadequate insulation can lead to power losses, malfunctions in electronic circuits, and, in the event of a voltage breakdown, destruction of the system and significant safety risks. Particularly at high voltages, where the electric field is stronger, insulation barriers can be breached.

[0007] It is therefore the object of the present invention to provide a coaxial transformer which can be used specifically for use in medium-frequency direct current systems in the medium voltage range and / or which offers improved electrical insulation and shielding in order to meet the high requirements for dielectric strength and safety in particular, wherein preferably a compact design and high power density are to be achieved at the same time.

[0008] This object is achieved by the features of the independent patent claims. Further advantageous embodiments of the solution proposed here are specified in the dependent patent claims. It should be noted that features individually listed in the dependent patent claims can be combined with one another in any technologically expedient manner and can define further embodiments of the invention. Furthermore, the features specified in the patent claims are specified and explained in more detail in the description, wherein further preferred embodiments of the invention can also be presented. According to a first aspect of the invention, the stated object is achieved by a coaxial transformer having the features of patent claim 1. The coaxial transformer has a coaxial cable forming a primary winding with an inner conductor and a conductive cable shield.The coaxial transformer further comprises a secondary conductor forming a secondary winding. The coaxial transformer has at least one magnetic core and a ground terminal that can be connected to a reference potential. The primary and secondary windings are each arranged in relation to the magnetic core. The ground terminal is electrically connected to the cable shield, allowing the inner conductor to be shielded by the cable shield.

[0009] As already mentioned, the coaxial transformer has a coaxial cable forming a primary winding with an inner conductor and a conductive cable shield. A coaxial cable is a type of electrical cable made up of multiple layers arranged concentrically around a common axis. The inner conductor forms the central core of the cable, which is preferably made of or with copper or a copper alloy. The inner conductor can, for example, consist of a mutually insulated bundle of thin strands, whereby the bundle is preferably a high-frequency strand (HF strand). An insulating layer, which can be referred to as a dielectric, is usually located around the inner conductor. The insulating layer usually keeps the inner conductor physically separate from the outer layers and is suitable for preventing electrical arcing. Above the insulating layer orThe conductive cable shield can be located on the dielectric and can preferably be formed by a rigid outer conductor in the form of a tube or pipe. The conductive cable shield can preferably be in the form of a conductive cable sheath. Alternatively or additionally, the conductive cable shield can be formed with or from a metallic braid and / or foil. This layer serves in particular to shield against external electromagnetic influences and to control the electric field, since this is held within the cable shield. An insulating sheath is preferably arranged over the cable shield and can be formed with or from a plastic and can protect the cable from environmental influences, mechanical damage and / or corrosion. The coaxial cable forming the primary winding advantageously makes it possible to achieve a mechanically robust and compact design of the coaxial transformer.This also advantageously minimizes stray inductances. The proximity between the inner conductor and the conductive cable shield can also advantageously ensure more efficient magnetic coupling, which can further improve the overall efficiency of the transformer.

[0010] The coaxial transformer has a secondary conductor forming a secondary winding. The secondary conductor preferably comprises a high-frequency stranded wire (HF stranded wire). The secondary conductor is, in particular, galvanically isolated from the primary winding. By using a galvanically isolated secondary conductor as the secondary winding, the conductive cable shield of the coaxial cable can advantageously be used to shield the inner conductor of the primary winding. It has surprisingly been found that the cable shield of the coaxial cable can provide excellent shielding against external electromagnetic interference when connected to a reference potential. This advantageously contributes to improved signal quality and reduced susceptibility of the coaxial transformer to interference, which can be particularly important in sensitive electronic applications.

[0011] The coaxial transformer also has at least one magnetic core. The magnetic core serves to conduct and / or amplify the magnetic field required for energy transfer between the primary and secondary windings of the coaxial transformer. A magnetic core is generally understood to be the area of ​​the magnetic core in which the magnetic field generated by the primary winding is conducted and induced, and which serves to induce a voltage in the secondary conductor. The core of the coaxial transformer can have areas through which no magnetic field is conducted and concentrated, or which contributes little or nothing to inducing the voltage in the secondary conductor. This can be particularly the case in areas of the magnetic core in which no winding of the primary or secondary winding is arranged. The magnetic core can be provided with or without a magnetic core.be made of soft iron, as this material advantageously has high magnetic permeability, meaning it can be easily magnetized and demagnetized. Alternatively, the magnetic core can be made of laminated silicon steel, amorphous metal, or ferrite. In laminated silicon steel, the laminations can reduce eddy current losses, while the silicon can increase the electrical resistance of the steel, thus reducing further losses. Amorphous metals generally have lower eddy current losses and very high magnetic permeability. Ferrite cores are often used in high-frequency transformers. Ferrites are generally ceramic, non-conductive materials that can reduce eddy current losses at high frequencies.

[0012] The coaxial transformer has a ground connection that can be connected to a reference potential or can be electrically connected to a reference potential. The ground connection serves in particular to safely discharge electrostatic charges. The ground connection advantageously provides a protective path for the current, particularly when the ground potential serves as the reference potential, so that particularly simple and robust voltage isolation can be achieved. Furthermore, this can result in minimal material input, particularly with regard to the insulation. The ground connection can form an interface for a grounding element that can be connected to the coaxial transformer. The ground connection can, for example, run (at least) in part within the coaxial cable. However, this section can be very short and only serve to lead the ground connection out of the coaxial cable.Alternatively or cumulatively, the ground connection can run (at least) partially outside the coaxial cable. The ground connection can be or run (at least) partially with a radial directional component to the outside. This can simplify contacting and routing of the ground connection. For example, the ground connection can run past the insulation sheath or through it. For example, the ground connection can extend through an area adjacent to an end of the insulation sheath. The end can be created by stripping the insulation sheath. Furthermore, the ground connection can extend at least partially through an area of ​​a cable termination. The cable termination is explained in more detail below. The cable termination can advantageously guide and / or protect the ground connection.In particular, the ground connection can be routed in such a way that it can electrically connect the conductive cable shield to a reference potential located outside the coaxial cable. For this purpose, the ground connection can be connected to a housing of the coaxial transformer at a portion or end portion. The housing can be connected to a grounding system to provide a safe path to ground. An example of a ground connection can be a wire or an electrical conductor provided in addition to the inner conductor and the conductive cable shield. The ground connection itself can be provided with electrical insulation.

[0013] The primary and secondary windings are each arranged in relation to the magnetic core. An arrangement in relation to the magnetic core is understood in particular to mean that the primary and secondary windings are arranged such that a magnetic flux can be generated in the core when a current, preferably an alternating current, flows through the primary winding. The core serves to conduct and concentrate the magnetic flux. The temporal change in the magnetic flux flowing through the core then induces a voltage in the secondary winding of the coaxial transformer. The induced voltage is the result of the change in the magnetic flux caused by the current in the primary winding. An arrangement of the primary and secondary windings in relation to the magnetic core is therefore preferably understood to mean any arrangement that causes a magnetic flux in the core and a voltage induction in the secondary conductor.The primary and secondary windings can be arranged or wound (at least) in sections around at least one (inner) partial region of the core. Alternatively or cumulatively, the primary and secondary windings can extend (at least) in sections within at least one (outer) partial region of the core. In particular, the primary winding and the secondary winding can run similarly or essentially parallel to one another, at least in sections. The ground connection is electrically connected to the cable shield, so that the inner conductor can be shielded by the cable shield. An electrical connection is understood, in particular, to mean that a current can be (efficiently) discharged via the ground connection to the reference potential. For example, a partial region or end region of the ground connection can be directly connected (e.g., by a material fit or a form fit) to a contact region of the cable shield.Another part or the other end of the earth connection can be connected to a reference potential.

[0014] In summary, it can be stated that a coaxial transformer can be provided which can be specifically designed for use in medium-frequency DC systems in the medium voltage range and / or offers improved electrical insulation and shielding in order to meet the high requirements for dielectric strength and safety as best as possible, while at the same time achieving a compact design and high power density.

[0015] The grounding connection preferably contacts the cable shield in a contact area, so that a current can flow from the conductive cable shield in the contact area to the grounding connection and discharge via the reference potential. By selecting a suitable contact area, an advantageously simple and compact design of the primary winding and the coaxial transformer can be achieved. The contact area can, for example, be located at an outer end section of the cable shield. It can, for example, advantageously be provided simply by removing the insulation sheath at the end.

[0016] In one embodiment, the magnetic core has a toroidal shape, wherein the primary and secondary windings are each wound in the form of a toroidal coil, wherein the core encompasses the primary and / or secondary winding at least in sections. A toroidal shape is understood in particular to be a geometric shape that resembles a ring. A toroidal shape usually has a circular, annular, or torus-shaped structure. A toroid is generally understood to be a body of rotation that is created by the rotation of a circle in three-dimensional space around an axis of rotation, wherein the axis of rotation lies outside the cross-section of the circle. In addition to the magnetic core, the primary and secondary windings each also have a toroidal shape, so that they can be regarded as toroidal coils. The primary and secondary windings therefore have a toroidal shape regardless of the magnetic core.Because the magnetic core surrounds the primary and / or secondary winding at least in sections, it is advantageously achieved that at least a section of the magnetic core lies radially outside the primary and / or secondary winding. This allows a particularly advantageous compact design while still maintaining the highest possible magnetic efficiency.

[0017] Preferably, the magnetic core is arranged at least partially radially outside a cross-section of the primary and / or secondary winding. The primary and / or secondary windings are further preferably arranged within, in particular in a hollow interior, of the toroidal core. This can result in a particularly compact design of the coaxial transformer compared to a conventional cylindrical coil. At the same time, this can significantly reduce the core volume and the magnetic path.

[0018] The toroidal core is preferably constructed in multiple parts. This means that the core can be formed from multiple segments. In one variant, the core can be formed from at least two segments, wherein the at least two segments can each be formed with a half-shell. The two half-shells can be connected to one another in a form-fitting or material-locking manner. This makes it possible to arrange the primary and / or secondary winding in the magnetic core in a particularly simple manner, thus making it particularly easy to manufacture the coaxial transformer. In a further advantageous variant, the toroidal core can be formed with a plurality of circular segments. A circular segment is understood to mean, in particular, a segment in the circumferential direction around the axis of rotation of the toroid. Accordingly, a free space can be formed between the segments.The free space can enable the primary and secondary windings to be led out particularly easily, making it particularly easy to connect the primary and secondary windings. Furthermore, this allows for greater flexibility in the choice of lead-through. The primary and secondary windings can be led out through any free space for connection. The earth connection can also be led out through any of the free spaces. For example, it is conceivable for the primary and secondary windings to be led out in opposite directions. A multi-part design of the toroidal core can, on the one hand, make the coaxial transformer particularly easy to manufacture and, on the other hand, allow the coaxial transformer to have improved heat dissipation, which can improve the efficiency and service life of the coaxial transformer under high loads.

[0019] In one embodiment, the toroidal coil has a winding axis that runs parallel to a rotational axis of the toroidal core. This specifically means that the turns of the toroidal coil of the primary and / or secondary winding are wound around an axis that is arranged parallel to the rotational axis of the magnetic core. Preferably, the winding axis of the primary and / or secondary winding corresponds to the rotational axis of the toroidal core. This allows for a particularly compact design.

[0020] In one embodiment, the toroidal coil has a circular cross-section, and the windings of the toroidal coil exhibit a tangential offset along the circular cross-section. Tangential offset refers, in particular, to the windings being offset in the circumferential direction of the cross-section. The tangential offset can be either clockwise or counterclockwise. The tangential offset allows for a compact and densely packed design.

[0021] The tangential offset is preferably calculated as the quotient of the circumference divided by the number of turns of the toroidal coil. The circumference is given by 2TT. With 6 windings, this results in a tangential offset of 2TT / 6 = TT / 3 = 60, so that the windings have a tangential offset of 60°. This can result in an advantageously defined and reproducible tangential offset of the primary and / or secondary winding.

[0022] The secondary winding is preferably arranged radially within a cross-section of the primary winding. Alternatively, the secondary winding can be arranged radially outside a cross-section of the primary winding. Since the coaxial cable generally has a larger cross-section than the secondary conductor, an internal space is created radially within the primary winding in which the secondary winding can be arranged. This makes particularly advantageous use of the available installation space of the coaxial transformer. A particularly advantageous use of the installation space can also be achieved if the secondary conductor is arranged outside the cross-section of the primary winding, since the secondary conductor can be arranged in a space between two windings. This has the advantage that this space is much easier to access.

[0023] In one embodiment, the coaxial cable has a cable termination at each end, whereby the cable termination connects the inner conductor to a primary terminal and controls the electric field from the primary terminal to the cable shield. The primary terminal is usually created by stripping and demolding the coaxial cable at the ends so that the inner conductor is exposed. The cable termination is intended to distribute the electric field created at the end of the stripped cable as evenly as possible. Without such control, the electric field can be concentrated at sharp edges or transitions, which can lead to high field strengths and possibly electrical breakdowns or flashovers. The cable terminations can enable the inner conductor to be safely fed through to the primary terminal.

[0024] The cable termination preferably has an electrically insulating cable sleeve. The electrically insulating cable sleeve serves, in particular, to ensure that the inner conductor is appropriately insulated in the area where the conductive cable shield has been removed. This enables the inner conductor to be led out safely. The secondary winding preferably does not have a cable termination. Since the secondary winding is, in particular, galvanically isolated from the primary winding and the dielectric of the coaxial cable ensures the voltage insulation of the primary winding, the secondary conductor can advantageously be connected directly to the secondary source, since the secondary conductor, in particular, does not require an earth connection or additional insulator. This enables a particularly simple construction and connection of the coaxial transformer.

[0025] The coaxial transformer preferably has a winding support. The winding support can contribute to simplifying the creation of the primary and / or secondary winding, in particular with a tangential offset. The winding support can enable simple creation of the primary and / or secondary winding by inserting the coaxial cable and / or the secondary conductor into the winding support, in particular into designated or specific areas (recesses and / or receptacles) of the winding support. The winding support can have a ring shape and recesses for accommodating the coaxial cable and / or the secondary conductor. The winding support is preferably made of an insulating material so that the winding support can remain in the coaxial transformer and be installed. This allows for particularly simple production of the coaxial transformer.

[0026] According to a second aspect of the invention, the stated object is achieved by a method having the features of patent claim 6. The method serves to produce a coaxial transformer. The method comprises providing at least one magnetic core, a coaxial cable with an inner conductor and a conductive cable shield, and a secondary conductor. The method further comprises processing the coaxial cable such that the conductive cable shield is accessible at least in sections. Furthermore, the method comprises establishing an electrical connection of the conductive cable shield to a ground connection. Finally, the method comprises creating a primary winding by winding the coaxial cable and creating a secondary winding by winding the secondary conductor. The method comprises processing the coaxial cable such that the conductive cable shield is accessible at least in sections.The coaxial cable is processed in particular such that the conductive cable shield is exposed at least in sections so that it can be contacted. As already mentioned, the coaxial cable may have an insulating sheath, so that the processing may comprise a (section-by-section) removal of the insulating sheath. The insulating sheath may be removed from a section of the circumference of the coaxial cable, so that only a section of the circumference of the conductive cable shield is accessible. Alternatively, the processing may comprise the removal of the insulating sheath over the entire circumference of the coaxial cable. This has the advantage that comparatively simple tools and methods for removing cable insulation can be used.

[0027] Furthermore, the method comprises establishing an electrical connection between the conductive cable shield and a grounding terminal. The electrical connection between the grounding terminal and the previously exposed conductive cable shield can be established using one of the following connection techniques for establishing an electrical connection: soldering, crimping, screwing, clamping, plugging, splicing, or using heat-shrink tubing. During soldering, the grounding terminal is soldered to the conductive cable shield. During crimping, the grounding terminal is mechanically connected to the conductive cable shield via a positive connection. During screwing, the grounding terminal is screwed to the conductive cable shield, whereby a screw made of conductive material can be used.With clamping, the ground connection is clamped force-fittingly to the conductive cable shield, preferably the ground connection is clamped between the dielectric or the insulation sheath and the conductive cable shield. With plugging, the ground connection is connected to the conductive cable shield via a special connector. The connector can be in the form of a socket. With splicing, the ground connection is wrapped around the conductive cable shield and then secured, preferably with a solder connection or heat shrink tubing. With heat shrink tubing, the ground connection is electrically connected to the conductive cable shield and held in place by heat shrink tubing. Heat shrink tubing can be used in the form of heat shrink and cold crimp tubing. The heat shrink tubing holds the ground connection to the conductive cable shield via a force-fitting connection.These connection techniques have the advantage that they allow a simple electrical connection of the earth terminal to the conductive cable shield.

[0028] The method further comprises creating a primary winding by winding the coaxial cable and creating a secondary winding by winding the secondary conductor. Creating the primary winding and the secondary winding can be performed in a single step. As already mentioned, the secondary conductor can be arranged radially inside or outside the primary winding. When creating the primary and secondary windings, the coaxial cable and the secondary conductor can be wound around a (common) winding axis, so that the primary and secondary windings can be used as winding packages for manufacturing the coaxial transformer.

[0029] The secondary winding can be created before the primary winding is created, with the primary winding being arranged around the secondary winding so that the secondary winding runs radially within a cross-section of the primary winding. Since the coaxial cable generally has a larger cross-section than the secondary conductor, a radial space is created within the primary winding in which the secondary winding can be arranged. This allows the installation space of the coaxial transformer to be utilized to its full potential.

[0030] The primary winding can be created before the secondary winding is created, with the secondary winding being arranged around the primary winding such that the secondary winding is arranged radially outside a cross-section of the primary winding. This allows advantageous use of the installation space. Advantageous use of the installation space can also be achieved if the secondary conductor is arranged outside the cross-section of the primary winding, since the secondary conductor can be arranged in a space between two windings. This has the advantage that this space is significantly easier to access. In one embodiment, processing the coaxial cable comprises at least stripping at least one section at at least one end of the coaxial cable and / or stripping at least one section at at least one end of the coaxial cable.Stripping at least a section of at least one end of the coaxial cable can comprise removing the insulation sheath or the dielectric. In general, stripping is understood to mean removing insulating material so that a layer underlying the insulating material is exposed. Stripping at least a section of at least one end of the coaxial cable can comprise removing the conductive cable shield. In this case, the conductive cable shield can be removed (at least) in sections so that the underlying layer is exposed. Sectional removal of material can also be referred to when the material is not removed over the entire circumference of the coaxial cable. This is particularly conceivable when connecting the ground connection.By processing the coaxial cable, the conductive cable shield and / or the inner conductor can be exposed in sections, allowing them to be connected to the ground terminal or the primary source. This allows for a particularly simple process for manufacturing a coaxial transformer.

[0031] In one embodiment, creating the primary winding and / or creating the secondary winding comprises creating a toroidal coil. A toroidal coil is understood in particular to be a coil that has the shape of a toroid. A toroid is understood in particular to be a geometric shape that resembles a ring. A toroidal shape has a circular, annular, or toroidal structure. A toroid is understood in particular to be a body of rotation that is created by rotating a circle in three-dimensional space around an axis of rotation, wherein the axis of rotation lies outside the cross-section of the circle. By creating a toroidal coil, it can be achieved that the magnetic core encompasses the primary and / or secondary winding at least in sections. This makes it particularly easy to insert the primary and / or secondary coil into the magnetic core or to accommodate it.Preferably, the primary and secondary windings are constructed such that their winding axes run parallel to a rotational axis of the toroidal core. This specifically means that the turns of the toroidal coil of the primary and / or secondary windings are wound around a (common) axis that is arranged parallel to the rotational axis of the magnetic core. Preferably, the winding axis of the primary and / or secondary winding corresponds to the rotational axis of the toroidal core. This allows for a particularly compact design.

[0032] In one embodiment, when creating the primary winding and / or the secondary winding, the turns of the primary winding and / or the secondary winding are wound with a tangential offset to one another along their circular cross-section. A tangential offset is understood in particular to mean that the turns in the cross-section are offset in the circumferential direction of the cross-section. The tangential offset can be either clockwise or counterclockwise. The tangential offset allows for a compact and densely packed design.

[0033] The tangential offset is preferably calculated as the quotient of the circumference divided by the number of turns of the toroidal coil. The circumference is given by 2TT. With 6 windings, this results in a tangential offset of 2TT / 6 = TT / 3 = 60, so that the windings have a tangential offset of 60°. This can result in a defined and reproducible tangential offset of the primary and / or secondary winding.

[0034] The secondary winding is preferably arranged radially within a cross-section of the primary winding. In this case, the secondary winding can be created before the primary winding is created. Alternatively, the secondary winding can be arranged radially outside a cross-section of the primary winding, so that the primary winding can be created before the secondary winding is created. Since the coaxial cable generally has a larger cross-section than the secondary conductor, an internal space is created in the radial direction within the primary winding in which the secondary winding can be arranged. This allows the installation space of the coaxial transformer to be used as effectively as possible. Good use of the installation space can also be achieved if the secondary conductor is arranged outside the cross-section of the primary winding, since the secondary conductor can be arranged in a space between two windings.This has the advantage that this gap is much easier to access.

[0035] In one embodiment, the method comprises attaching a cable termination to each end of the primary winding. The ends of the primary winding are connected, in particular, to a primary terminal by stripping and demolishing the coaxial cable at the ends so that the inner conductor is exposed. The cable termination is intended to evenly distribute the electric field created at the end of the stripped cable. Without such control, the electric field can be concentrated at sharp edges or transitions, which can lead to high field strengths and possibly electrical breakdowns or flashovers. The cable terminations can enable secure passage of the inner conductor to the primary terminal. Attaching the cable termination can result in a particularly simple method for manufacturing the coaxial transformer.

[0036] Preferably, the attachment of the cable termination and the establishment of the electrical connection of the conductive cable shield to a ground terminal are carried out at least partially in parallel or simultaneously. For the attachment of the cable termination and the establishment of the electrical connection of the conductive cable shield to a ground terminal, the coaxial cable can be stripped or dismantled at least in sections. By simultaneously attaching the cable termination and establishing the electrical connection of the conductive cable shield to the ground terminal, a particularly time-efficient method can be provided.

[0037] The method preferably comprises providing a winding carrier. The winding carrier can be used particularly advantageously for creating the primary and / or secondary winding, in particular with a tangential offset. The winding carrier can enable simple creation of the primary and / or secondary winding by inserting the coaxial cable and / or the secondary conductor into the winding carrier. The coaxial cable can also be fixed in place by gluing during insertion. The winding carrier can have a ring shape and recesses for receiving the coaxial cable and / or the secondary conductor. The winding carrier is preferably made of or with an insulating material so that the winding carrier can remain in the coaxial transformer and be installed. This makes it particularly easy to manufacture the coaxial transformer.

[0038] Further features, advantages, and possible applications of the present invention will become apparent from the following description of the exemplary embodiments and the figures. All described and / or illustrated features, individually and in any combination, constitute the subject matter of the invention, regardless of their composition in the individual claims or their references. In the figures, the same reference numerals continue to represent the same or similar objects.

[0039] Figure 1 shows a schematic representation of a coaxial cable,

[0040] Figures 2a and 2b show schematic representations of a first embodiment of a coaxial transformer according to the first aspect of the present invention,

[0041] Figures 3a and 3b show schematic representations of the first embodiment of the coaxial transformer according to the first aspect of the present invention from Figures 2a and 2b,

[0042] Figure 4 shows a schematic representation of an alternative embodiment of the coaxial transformer according to the first aspect of the present invention from Figures 2a to 3b,

[0043] Figures 5a and 5b show schematic representations of a second embodiment of a coaxial transformer according to the first aspect of the present invention with the coaxial cable from Figure 1,

[0044] Figure 6 shows a flow chart of a method for manufacturing a coaxial transformer according to the second aspect of the present invention. Figure 1 shows a schematic representation of a coaxial cable 1. The coaxial cable 1 is a type of electrical cable constructed from multiple layers arranged concentrically around a common axis. The coaxial cable 1 has an inner conductor 3, a dielectric 5, and a conductive cable shield 7. The inner conductor 3 forms the central core of the coaxial cable 1, which is preferably in the form of an RF stranded wire or made of copper or a copper alloy. Surrounding the inner conductor 3 is the dielectric 5, which represents an insulating layer that keeps the inner conductor 3 physically separate from the outer layers and is intended to prevent electrical arcing.The conductive cable shield 7, which is preferably formed by a rigid outer conductor in the form of a tube, is located above the dielectric 5. Alternatively, the conductive cable shield 7 can consist of a metallic braid and / or foil. This layer serves to shield against external electromagnetic influences and to control the electric field. An insulating sheath 9, which can also be referred to as a protective sheath, is arranged above the cable shield 7. The insulating sheath 9 is made of a plastic and protects the coaxial cable 1 from environmental influences, mechanical damage, and corrosion.

[0045] The coaxial cable 1 has a ground connection 11 that can be connected to a reference potential. The ground connection 11 serves to safely discharge electrostatic charges and can also have an insulating sheath. The ground connection 11 provides a protective path for the current, particularly when the ground potential serves as the reference potential, thus achieving particularly simple and robust voltage insulation. Furthermore, this results in minimal material input, particularly with regard to the insulation. The ground connection 11 contacts the cable shield 7 in a contact area 13, so that a current can flow from the conductive cable shield 7 in the contact area 13 to the ground connection 11 and discharge via the reference potential. By selecting a suitable contact area 13, a particularly simple and compact design of the coaxial cable 1 is achieved.

[0046] The coaxial cable 1 has a cable termination 15. The coaxial cable 1 has two ends, not shown, with a cable termination 15 arranged at each end. The cable termination 15 serves to connect the inner conductor 3 to a primary connection and controls the electric field from the primary connection to the cable shield 7. The primary connection is created by stripping and demolding the coaxial cable 1 at the ends so that the inner conductor 3 is exposed. The cable termination 15 is intended to evenly distribute the electric field created at the end of the stripped coaxial cable 1. Without such control, the electric field can be concentrated at sharp edges or transitions, which can lead to high field strengths and possibly to electrical breakdowns or flashovers. The cable terminations 15 enable the inner conductor to be safely fed through to the primary connection.

[0047] The cable termination 15 serves as an electrically insulating cable sleeve, which serves to ensure that the inner conductor 3 is appropriately insulated in the area where the conductive cable shield 7 has been removed. This enables the inner conductor 3 to be safely routed out. The cable termination 15 can also serve to insulate the contact area 13. The cable termination 15 can also serve to guide and / or protect the ground connection 11.

[0048] Figures 2a and 2b show schematic representations of a first embodiment of a coaxial transformer 17 with the coaxial cable 1 from Figure 1. In the first embodiment, the coaxial transformer 17 has a primary winding 19 formed by the coaxial cable 1. The coaxial transformer 17 also has a secondary conductor 21 forming a secondary winding 23 of the coaxial transformer 17. The primary winding 19 and the secondary winding 23 are enclosed by a magnetic core 25. The magnetic core 25 serves to conduct and amplify the magnetic field required for energy transfer between the primary and secondary windings 19, 23 of the coaxial transformer 17.In the first embodiment, the magnetic core 25 has a toroidal shape, with the primary and secondary windings 19, 23 each wound in the form of a toroidal coil, with the magnetic core 25 at least partially enclosing the primary and / or secondary windings 19, 23. A toroidal shape is understood to be a geometric shape resembling a ring. A toroidal shape has a circular, annular, or torus-shaped structure. A toroid is understood to be a body of rotation created by the rotation of a circle in three-dimensional space around an axis of rotation, wherein the axis of rotation lies outside the cross-section of the circle. In addition to the magnetic core 25, the primary and secondary windings 19, 23 each also have a toroidal shape, so that they can be regarded as toroidal coils. The primary and secondary windings 19, 23 therefore have a toroidal shape independent of the magnetic core 25.Because the magnetic core 25 at least partially encompasses the primary and / or secondary windings 19, 23, at least a portion of the magnetic core 25 is located radially outside the primary and / or secondary windings 19, 23. This results in a particularly compact design with high magnetic efficiency.

[0049] The magnetic core 25 is arranged, at least in sections, radially outside a cross-section of the primary and / or secondary windings 19, 23. The primary and / or secondary windings 19, 23 are arranged within, in particular in a hollow interior space 27, of the toroidal core 25. This results in a particularly compact design of the coaxial transformer 17. At the same time, this significantly reduces the core volume and the magnetic path.

[0050] The magnetic core 25 can be made of soft iron, as this material has a high magnetic permeability, meaning it can be easily magnetized and demagnetized. Alternatively, the magnetic core 25 can comprise laminated silicon steel, amorphous metal, or ferrite. In laminated silicon steel, the laminations reduce eddy current losses, while the silicon increases the electrical resistance of the steel, which further reduces losses. Amorphous metals have lower eddy current losses and a very high magnetic permeability. Ferrite cores are used in high-frequency transformers. Ferrites are ceramic, non-conductive materials that reduce eddy current losses at high frequencies. Figures 3a and 3b show schematic representations of the first embodiment of the coaxial transformer 17 from Figures 2a and 2b.Figures 3a and 3b show the coaxial transformer 17 with the primary winding 19 and the secondary winding 23. The secondary winding 23 is arranged radially within a cross-section of the primary winding 19. Since the coaxial cable 1 generally has a larger cross-section than the secondary conductor 21, an interior space is created in the radial direction within the primary winding 19 in which the secondary winding 23 can be arranged. This advantageously utilizes the installation space of the coaxial transformer 17.

[0051] Figure 3b shows a tangential offset of the primary and secondary windings 19, 23. A tangential offset means that the primary and secondary windings 19, 23 are offset in the cross-section in the circumferential direction of the cross-section. The tangential offset can be either clockwise or counterclockwise. Figure 3b shows a coaxial transformer 17 with a primary winding 19 and a secondary winding 23, each having six windings. The primary winding 19 has a counterclockwise tangential offset in that the windings X, X' and X" are each offset in the circumferential direction along the winding. The secondary winding 23 also has a tangential offset because the windings of the secondary winding 23 run between the windings X, X', X". All windings have the same tangential offset. The tangential offset achieves a compact and densely packed design.

[0052] In the present embodiment, the coaxial transformer 17 has a winding support 29. The winding support 29 can be used to create the primary and / or secondary windings 19, 23, in particular with a tangential offset. The winding support 29 enables simple creation of the primary and / or secondary windings 19, 23 by inserting the coaxial cable 1 and / or the secondary conductor 21 into the winding support 29. The winding support 29 has a ring or toroidal shape and recesses for receiving the coaxial cable 1. The winding support 29 is preferably made of an insulating material so that the winding support 29 can remain in the coaxial transformer 17 and be installed. This results in particularly simple production of the coaxial transformer 17. Figure 4 shows a schematic representation of an alternative embodiment of the coaxial transformer 17 from Figures 2a to 3b.The coaxial transformer 17 of the alternative embodiment differs from the coaxial transformer 17 of the first embodiment shown in Figures 2a to 3b in that the secondary winding 23 runs radially inside the primary winding 19. Since the coaxial cable 1 generally has a larger cross-section than the secondary conductor 21, an interior space is created in the radial direction within the primary winding 19 in which the secondary winding 23 is arranged. The secondary winding 23 has a tangential offset, which is shown by the offset of the turns Y, Y', Y". The tangential offset is created analogously to the tangential offset of the first embodiment shown in Figures 2a to 3b, so reference is made to the explanations for the first embodiment. Because the secondary winding 23 runs radially inside the primary winding 19, the installation space of the coaxial transformer 17 is advantageously utilized.A winding carrier not shown here can also be used to create the secondary winding 23.

[0053] Figures 5a and 5b show schematic representations of a second embodiment of a coaxial transformer 17 with the coaxial cable 1 from Figure 1, wherein Figure 5a shows a schematic perspective view of the coaxial transformer 17, while Figure 5b shows a schematic plan view of the coaxial transformer 17. Figure 5b also shows the ground terminal 11, which is connected to a ground 31. By connecting the ground terminal 11 to the ground 31, advantageous electrical insulation and shielding of the electric field of the inner conductor 3 is achieved.

[0054] The coaxial transformer 17 of the second embodiment differs from the coaxial transformer 17 of the first embodiment in that the primary and secondary windings 19, 23 are wound in the form of cylindrical coils. This has the advantage that cylindrical coils generally have a simpler structure. In particular, the coaxial transformer 17 of Figures 5a and 5b does not require a winding support 29, as shown in Figure 3b. Figure 6 shows a flow chart of a method 100 for producing a coaxial transformer 17 according to the second aspect of the present invention. The method 100 is for producing a coaxial transformer 17 and comprises, in a first step 101, providing at least one magnetic core 25, a coaxial cable 1 with an inner conductor 3 and a conductive cable shield 7, and a secondary conductor 21.

[0055] In a second step 102, the method 100 comprises processing the coaxial cable 1 such that the conductive cable shield 7 is accessible at least in sections. The coaxial cable 1 is processed such that the conductive cable shield 7 is exposed at least in sections so that contact can be made therewith. As already mentioned, the coaxial cable 1 has an insulating sheath 9, so that the processing comprises removing the insulating sheath 9. The insulating sheath 9 can either be removed from a section of the circumference of the coaxial cable 1, so that only a section of the circumference of the conductive cable shield 7 is accessible. Alternatively, the processing can comprise removing the insulating sheath 9 over the entire circumference of the coaxial cable 1. This has the advantage that known tools and methods for removing cable insulation can be used for this purpose.

[0056] The second step 102 comprises stripping the insulation of at least one section at at least one end of the coaxial cable 1 and / or stripping the sheath of at least one section at at least one end of the coaxial cable 1. Stripping at least one section at at least one end of the coaxial cable 1 can comprise removing the insulating sheath 9 or removing the dielectric 5. In general, stripping is understood to mean the removal of insulating material so that a layer underlying the insulating material is exposed. Stripping at least one section at at least one end of the coaxial cable 1 can comprise removing the conductive cable shield 7. In this case, the conductive cable shield 7 can be removed at least in sections so that the underlying layer is exposed.Sectional removal of material can also be defined as the removal of material from the entire circumference of the coaxial cable 1. This is particularly relevant when connecting the ground terminal 11. By processing the coaxial cable 1, the conductive cable shield 7 and / or the inner conductor 3 are exposed in sections so that they can be connected to the ground terminal 11 or a primary source. This results in a particularly simple method 100 for producing a coaxial transformer 17.

[0057] In a third step 103, the method 100 comprises establishing an electrical connection between the conductive cable shield 7 and a ground terminal 11. The electrical connection between the ground terminal 11 and the previously exposed conductive cable shield 7 can be established using one of the following connection techniques for establishing an electrical connection: soldering, crimping, screwing, clamping, plugging, splicing, or using heat-shrink tubing.

[0058] In a fourth step 104, the method 100 comprises creating a primary winding 19 by winding the coaxial cable 1, and in a fifth step 105, creating a secondary winding 23 by winding the secondary conductor 21. The creation of the primary winding 19 and the creation of the secondary winding 23 can be performed in one step. As already mentioned, the secondary conductor 21 can be arranged radially inside or outside the primary winding 19. When creating the primary and secondary windings 19, 23, the coaxial cable 1 and the secondary conductor 21 are wound around a winding axis so that the primary and secondary windings 19, 23 can be used as winding packages for producing the coaxial transformer 17. The fourth step 104 and the fifth step 105 comprise creating a toroidal coil for the primary winding 19 and / or the secondary winding 23.By creating a toroidal coil, the magnetic core 25 at least partially surrounds the primary and / or secondary windings 19, 23. This allows the primary and / or secondary windings 19, 23 to be inserted into or received by the magnetic core 25 particularly easily. When creating the toroidal coil in the fourth and fifth steps 104, 105, the turns of the primary and secondary windings 19, 23 are wound along their circular cross-sections with a tangential offset from one another.

[0059] The method 100 for producing a coaxial transformer 17 can also comprise, in the fourth or fifth step 104, 105, inserting the primary and / or secondary windings 19, 23 into at least part of the magnetic core 25. As already mentioned, the magnetic core 25 can consist of several segments, wherein the several segments consist of at least two half-shells. In this case, the primary and secondary windings 19, 23 are created in the fourth step and then placed in one of the half-shells of the magnetic core 25. Subsequently, the magnetic core 25 or the segments of the magnetic core 25 are closed, so that the primary and secondary windings 19, 23 are enclosed by the magnetic core 25 or are encompassed in sections.

[0060] In a sixth step 106, the method 100 comprises attaching a cable termination 15 to each end of the primary winding 19. The ends of the primary winding 19 are connected to a primary terminal by stripping and removing the insulation from the coaxial cable 1 at the ends, so that the inner conductor 3 is exposed. The cable termination 15 is intended to evenly distribute the electric field created at the end of the stripped cable. Without such control, the electric field can be concentrated at sharp edges or transitions, which can lead to high field strengths and possibly electrical breakdowns or flashovers. The cable terminations 15 enable the inner conductor 3 to be securely fed through to the primary terminal. The attachment of the cable termination 15 results in a particularly simple method 100 for manufacturing the coaxial transformer 17.

[0061] Additionally, it should be noted that "comprising" does not exclude other elements or steps, and "a" or "an" does not exclude a plurality. Furthermore, it should be noted that features described with reference to one of the above embodiments can also be used in combination with other features of other embodiments described above. Reference symbols in the claims are not to be considered as limiting.

[0062] Coaxial cable inner conductor dielectric cable shield insulation sheath

[0063] Earth connection Contacting area Cable termination Coaxial transformer Primary winding Secondary conductor

[0064] Secondary winding magnetic core interior winding carrier grounding

[0065] Procedure first step second step third step fourth step fifth step sixth step

Claims

Patent claims 1. Coaxial transformer (17) with a coaxial cable (1) forming a primary winding (19) with an inner conductor (3) and a conductive cable shield (7), a secondary conductor (21) forming a secondary winding (23), at least one magnetic core (25), and an earth connection (11) which can be connected to a reference potential, wherein the primary and secondary windings (19, 23) are each arranged in relation to the magnetic core (25), wherein the earth connection (11) is electrically connected to the cable shield (7) so that the inner conductor (3) can be shielded by the cable shield (7).

2. Coaxial transformer (17) according to claim 1, wherein the magnetic core (25) has a toroidal shape, wherein the primary and secondary windings (19, 23) are each wound in the form of a toroidal coil, wherein the core (25) surrounds the primary and / or secondary windings (19, 23) at least in sections.

3. Coaxial transformer (17) according to one of claims 1 or 2, wherein the toroidal coil has a winding axis running parallel to a rotation axis of the toroidal core (25).

4. Coaxial transformer (17) according to one of the preceding claims 1 to 3, wherein the toroidal coil has a circular cross-section and the turns of the toroidal coil have a tangential offset along the circular cross-section.

5. Coaxial transformer (17) according to one of the preceding claims, wherein the coaxial cable (1) has a cable termination (15) at each end, wherein the cable termination (15) connects the inner conductor (3) with a primary terminal and controls the electric field from the primary terminal to the cable shield (7).

6. A method (100) for manufacturing a coaxial transformer (17), the method (100) comprising at least the following steps: Providing at least one magnetic core (25), a coaxial cable (1) with an inner conductor (3) and a conductive cable shield (7) and a secondary conductor (21), Processing the coaxial cable (1 ) so that the conductive cable shield (7) is accessible at least in sections, Establishing an electrical connection of the conductive cable shield (7) to an earth terminal (11), Creating a primary winding (19) by winding the coaxial cable (1 ), and Creating a secondary winding (23) by winding the secondary conductor (21).

7. A method (100) for manufacturing a coaxial transformer (17) according to claim 6, wherein the processing of the coaxial cable (1) comprises at least one of the following steps: Stripping at least one section at at least one end of the coaxial cable (1) and / or Stripping at least one section at at least one end of the coaxial cable (1).

8. A method (100) for manufacturing a coaxial transformer (17) according to claim 6 or 7, wherein the creation of the primary winding (19) and / or the creation of the secondary winding (23) comprises the creation of a toroidal coil.

9. Method (100) for producing a coaxial transformer (17) according to one of claims 6 to 8, wherein, when creating the primary winding (19) and / or the secondary winding (23), the turns of the primary winding (19) and / or secondary winding (23) are wound along their circular cross-section with a tangential offset to one another.

0. Method (100) for manufacturing a coaxial transformer (17) according to one of the preceding claims 6 to 9, wherein the method (100) comprises the following step: Attaching a cable termination (15) to each end of the primary winding (19).

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