Transformer, circuitry and magnetic resonance imaging apparatus

Abstract

A transformer comprising a first coil (2) and at least one second coil (3, 4), which first and second coils each enclose a common core (9) along a longitudinal axis (10), wherein the first coil (2) is one or more series-connected winding groups (5) of a plurality of windings (6) and the second coil (3, 4) comprises one or more parallel-connected individual windings (7, 8), wherein along the longitudinal axis (10) at the core (9) a winding group (5) or at least one of the winding groups (5) is arranged between two individual windings (7, 8) and / or an individual winding (7, 8) or at least one of the individual windings (7, 8) is arranged between two winding groups (5).

Description

Transformers, circuit systems, and magnetic resonance imaging devices Technical Field

[0001] This invention relates to a transformer comprising a first coil and at least one second coil, the first and second coils respectively surrounding a circumference of a common core extending along a longitudinal axis. Furthermore, this invention relates to a circuit system and a magnetic resonance imaging apparatus. Background Technology

[0002] In many applications, it is necessary to operate transformers at high switching frequencies, thereby minimizing the space requirements of the transformer and / or enabling low-cost manufacturing of the transformer and / or the circuitry system including the transformer. Such applications can be found, for example, in transformers used in switching power supplies.

[0003] However, at high switching frequencies, the skin effect causes alternating current to conduct at the surface of the transformer coil, limiting the skin penetration depth of the conductor used to form the coil. The use of conductors with large cross-sections, such as radio frequency stranded wires, has the disadvantage that contact with the inner core of the stranded wire cannot be guaranteed at the end of the coil formed by the stranded wire. This is because, for example, contact is only made with the outer stranded wire when using cable terminals or by means of soldering and / or clamping connections, making current conduction within the stranded wire impossible, or at least unreliable.

[0004] Besides the skin effect, the use of transformers at high switching frequencies can also be limited by the transformer's leakage inductance. Especially when the transformer has a high turn ratio, leakage inductance is very important as a parasitic effect because it counteracts the high current transmission in the transformer at high switching frequencies. Summary of the Invention

[0005] Therefore, the objective of this invention is to provide an improved transformer, which is particularly useful in situations involving high switching frequencies and / or high currents.

[0006] To achieve the aforementioned objective, in a transformer of the type mentioned at the beginning, according to the present invention, the first coil is one or more winding groups connected in series, and the second coil includes one or more individual windings connected in parallel, wherein at the core along the longitudinal axis, the winding group or at least one winding group is disposed between two individual windings and / or the individual winding or at least one individual winding is disposed between two winding groups.

[0007] The first coil is formed by one or more winding groups connected in series. The second coil comprises one or more individual windings connected in parallel, resulting in a high transformation ratio for power transfer from the first coil to the second coil. Advantageously, a small leakage inductance between the first and second coils is achieved through the geometric arrangement of the first and second coils along the longitudinal axis of the core. This arrangement of the coils also allows for a compact structural shape of the transformer.

[0008] This results in the following advantages: no additional capacitor is needed to compensate for leakage inductance. Furthermore, the transformer can operate at high frequencies due to the arrangement of the first and second coils, and generates high output current, especially when the first coil is used as the primary coil and the second coil as the secondary coil.

[0009] Compared to conventional transformers, which operate at lower frequencies, such as resonant converters, it is advantageous to produce transformers or circuit systems that include transformers at a lower cost because additional components, such as capacitors for compensating for leakage inductance, can be omitted. This also reduces the space requirements for transformers, which is particularly advantageous for circuit systems that include transformers.

[0010] The arrangement of a single winding between two winding groups, or the arrangement of a winding group between two single windings, can achieve up to 100% high surface overlap between the windings of the first and second coils. This can be achieved by advantageously arranging the winding group of the first coil and the single winding of the second coil at the core, ensuring that the field distribution between the first and second coils is at least substantially the same. This results in a small leakage inductance when coupling the first and second coils.

[0011] High surface overlap is achieved by having one or more winding groups of the first coil and one or more individual windings of the second coil staggered along the longitudinal axis at the core, thereby each wrapping around the same surface corresponding to the cross-sectional shape of the core, wherein these surfaces overlap when viewed in the longitudinal direction. Additionally, surface overlap can be improved by having individual windings and winding groups that are at least substantially identical, so that surface overlap can also be achieved between the coils themselves.

[0012] The individual windings of the second coil can be configured planarly to overlap with a winding group, which, for example, comprises multiple windings made of conductive metal wire. The planar extension of the individual windings along a direction orthogonal to the longitudinal axis can, in particular, correspond to the extension of at least one adjacent winding group along a direction orthogonal to the longitudinal axis. Specifically, the extensions of all individual windings and all winding groups of the transformer along the direction orthogonal to the longitudinal axis are identical or at least substantially identical.

[0013] The core may consist of one or more core elements arranged directly abutting each other. Particularly along the longitudinal axis, the core may have at least a partial cylindrical or square shape, such that a first coil and at least one second coil can be arranged around the core along the longitudinal axis.

[0014] According to the invention, a first coil may comprise a plurality of winding groups connected in series, and a second coil may comprise a plurality of individual windings connected in parallel, wherein the winding groups and individual windings are alternately arranged along the longitudinal axis at the core. In particular, it may be proposed that the number of individual windings in the second coil differs from the number of winding groups in the first coil by one, thereby enabling the alternating arrangement of winding groups and individual windings along the longitudinal axis of the core. Here, a row of alternately arranged individual windings and winding groups may, at their outer ends, consist of either individual windings or winding groups, depending on which number is larger.

[0015] It is feasible for the first coil to comprise between four and ten, particularly six, winding groups, and the second coil to comprise between four and ten, particularly seven, individual windings connected in parallel. In the case of six winding groups for the first coil and seven individual windings for the second coil, for example, when manufacturing a transformer, it is possible to alternately arrange the individual windings of the winding groups along the core, starting with the individual windings of the second coil. However, other numbers of winding groups and / or the first coil may also be used depending on the requirements of the transformer.

[0016] In a preferred embodiment of the invention, the transformer may include a plurality of second coils, wherein individual windings of the second coils are arranged in pairs adjacent to each other at the core as at least one group of individual windings, each comprising a single winding of a second coil. To achieve the lowest possible leakage inductance of the transformer, even with a plurality of second coils, by providing the most similar field distribution between the first and second coils, the individual windings of the second coils are arranged at the core as separate groups of individual windings. Here, the group of individual windings may be arranged between two groups of windings of the first coil, or the winding group of the first coil may be arranged between two groups of individual windings. The individual windings of the second coils are at least partially insulated from each other to achieve electrical isolation of the second coils.

[0017] In particular, each of the second coils can have the same number of individual windings connected in parallel, such that all the individual windings of the second coil can be arranged as a single winding group at the core of the transformer. For example, it is feasible for the transformer to include two second coils, each having one or more individual windings connected in parallel. Here, the second coils can be connected in series when used as secondary coils or as the output of the transformer, such that a half-wave of the alternating current transmitted via the transformer can be intercepted at each of the two second coils.

[0018] According to the invention, one or more winding groups can be respectively disposed at insulated winding carriers, wherein the winding carriers insulate the winding groups relative to the core and relative to adjacent one or more individual windings. In the core of the transformer, which is at least partially cylindrical, the winding carriers can be configured, for example, as sleeves, each sleeve having a ring disposed at its end. The winding groups disposed at the winding carriers can here be wound over the outer circumference of the sleeve and surrounded by the rings at the end.

[0019] The winding carrier is constructed of an electrically insulating material, allowing the winding group to be positioned between the rings located at the ends at the winding carrier, so that the winding group is insulated relative to the core and / or relative to at least one adjacent individual winding. The winding carrier can be made of plastic, for example, and has a thickness between 0.1 mm and 1 mm, particularly 0.4 mm. Other insulation thicknesses may also be selected in relation to the power to be converted by the transformer or the voltage applied to the first coil and / or at least one second coil.

[0020] In a preferred embodiment of the invention, it may be proposed that one or more winding groups of the first coil comprise a total of between 50 and 200 windings, particularly between 60 and 80. The windings of the first coil are hereby specifically divided into multiple winding groups, wherein the number of windings in each winding group corresponds specifically to the total number of windings of the first coil divided by the number of winding groups. For example, a first coil having 66 windings may be divided into six winding groups, each having eleven windings. It is also possible to select the number of windings and / or the division of windings into winding groups according to the intended use of the transformer.

[0021] According to the invention, one or more individual windings may be formed from planar winding elements. The winding elements may be at least partially annular disk-shaped to form the windings. The width of the annular disk-shaped region may correspond in particular to the width of the winding group, allowing for planar overlap between the annular disk-shaped section and one or more winding groups.

[0022] The winding element may have an opening in which the core of the transformer may be disposed. The shape of the opening may correspond to the shape of the cross-section of the core in which a single winding or group of windings is disposed. In addition to the annular disc-shaped winding section, the winding element may also have one or more contact sections, as described in more detail below.

[0023] By configuring a single winding as a planar winding element, a large surface area of ​​the single winding is achieved, which, due to the resulting skin effect, is suitable for transformer operation at high frequencies. Simultaneously, the planar winding element configuration of the single winding enables a minimized power cross-section, advantageously reducing the overall material required to construct at least one coil. In this way, a minimum power cross-section is achieved with a high surface area of ​​the second coil. This advantageously results in excessively low ohmic losses, for example, in the case of high switching frequencies of transformers used in switching power supplies or in the case of high-frequency AC currents. Furthermore, the reduction in material used to construct the second coil advantageously allows for a high volume-dependent power density of the transformer.

[0024] According to the invention, the winding element can be made of conductive sheet metal and / or conductive film, particularly as a stamped part. In particular, in transformers having more than one second winding, the winding element can have an insulating portion, at least in the region of the winding section of the winding element located at the core, so as to electrically insulate two side-by-side winding elements of two different second coils relative to each other. Making the winding element from conductive sheet metal and / or conductive film into a stamped part enables simple and low-cost production of the transformer.

[0025] The winding element can be made of, for example, sheet metal and / or thin film copper. The thickness of the winding element, i.e., its extension along the longitudinal axis of the core, can be selected in particular in relation to the frequency or switching frequency of the alternating current to be transmitted via the transformer, at which the transformer operates. The thickness of the winding element can take into account the resulting skin effect and is, for example, at least twice the skin penetration depth. In this way, flux guidance through the transformer core is also achieved in the region of the second coil. According to the invention, the winding element can have a thickness between 0.1 mm and 5 mm, particularly between 0.5 mm and 2 mm, preferably 1 mm, along the longitudinal axis.

[0026] In a preferred embodiment of the invention, one or more winding elements may each have two contact segments, wherein the contact segments extend outward from the core, and wherein the contact segments of one or more winding elements are respectively connected to a common connecting element extending along the longitudinal axis.

[0027] Through contact sections, the winding elements forming a single winding of at least one second coil can be electrically connected to each other. In particular, in two second coils, the contact sections of the winding elements of each coil can be connected to a common connecting element extending along the longitudinal axis, such that the two second coils can be electrically contacted via said connecting element. The connecting element can here induce electrical contact and / or mechanical fixation of the winding elements via corresponding contact sections connected to the connecting element.

[0028] According to the present invention, a transformer can be fixed via a connecting element, with its core held at the second coil in a free-oscillating manner. The transformer can be fixed to a busbar, for example, via a connecting element. The connecting element can be, for example, a bolt made of a conductive metal, such as copper or brass. Spacer elements can be provided between the contact sections of two individual windings or groups of individual windings of a winding group in which the first coil is disposed, the thickness of which corresponds particularly to the thickness of the winding group, to achieve a stable connection between the contact sections and the connecting element. The spacer elements can be, for example, made of a conductive metal to achieve both mechanical stability and conductive fixation of the contact sections via the connecting element. The spacer elements can be, for example, made of a conductive metal, such as galvanized copper.

[0029] When fixing the transformer via connecting elements, it is feasible to have the transformer carried by a single winding of a second coil as the winding element. This allows the transformer core to be arranged to oscillate freely. This ease of placement of the transformer advantageously allows the core, which can withstand electromagnetic forces, to oscillate at least within a certain range, thus advantageously preventing damage to the core and / or the transformer.

[0030] According to the present invention, an additional contact segment of the winding element extends at an angle to the contact segment of the winding element connected to the connecting element in a plane orthogonal to the longitudinal axis. The winding elements of the second coil extend in a plane orthogonal to the longitudinal axis of the core. In a planar winding element, these two contact segments extend in a plane orthogonal to the longitudinal axis of the core.

[0031] When one contact segment is connected to the connecting element, the other contact segment can extend at an angle relative to the contact segment connected to the connecting element, thus enabling lateral contact of the contact segments and thus a single winding. Advantageously, in this arrangement, when two second coils are arranged at the transformer, if the winding elements are arranged at the core with different orientations, identically shaped winding elements can be used for the individual windings of the two second coils respectively. In this way, the other contact segments are angled on different sides relative to the contact segment of the individual winding connected to the common connecting element. Thus, the second coils can make lateral contact with each other separately. Furthermore, the use of identically shaped winding elements simplifies the manufacture of the transformer.

[0032] According to the invention, the core may be made of a ferrite material, particularly a ferrite polymer material. The core may, for example, be at least partially cylindrical or square, such that winding groups and individual windings can be disposed at the core. The core may be composed of one or more elements, wherein a core composed of multiple elements may, for example, be combined into a closed yoke or similar shape to enable the guiding of magnetic flux in the transformer.

[0033] In a preferred embodiment of the invention, the core, the first coil, and / or the second coil are at least partially encapsulated with a sealing material. This protects the transformer from external influences and from damage to the core and coils.

[0034] A circuit system according to the invention is proposed, comprising a current source and a transformer according to the invention. The current source is connected in particular to one coil of the transformer. To generate a current with high intensity and a low voltage, the current source can be connected in particular to a first coil, which serves as a primary coil, wherein a high-intensity output current can be generated at the second coil, which serves as a secondary coil, provided that the turns ratio of the first coil to the second coil is large.

[0035] In a preferred embodiment of the invention, a current source is connected to the first coil of the transformer, and alternating current can be input into the first coil through the current source. One or more individual windings are each formed by planar winding elements, the thickness of which along the longitudinal axis is greater than twice the penetration depth of the alternating field generated by the first coil based on the alternating current at the second coil. The penetration depth is here produced by the skin effect of the alternating current conducted at the second coil. The thickness of the coil can here particularly have a value between twice and ten times the penetration depth. In this way, flux guidance through the transformer core is also achieved in the region of the second coil.

[0036] All the advantages and design schemes described above with respect to the transformer according to the invention also apply to the circuit system and vice versa.

[0037] The magnetic resonance imaging apparatus according to the invention comprises at least one transformer according to the invention and / or at least one circuit system according to the invention. The transformer or circuit system including the transformer can be used to supply current to one or more magnets of the magnetic resonance imaging apparatus. The high current generated via the transformer can advantageously be used to magnetize or form a field in one or more magnets of the magnetic resonance imaging apparatus. A compact construction of the transformer can be advantageously achieved using relatively little material to form the transformer core and coils. This avoids or at least reduces the interference of the transformer, located near the magnets of the magnetic resonance imaging apparatus, on imaging.

[0038] All the advantages and designs described above with respect to the transformer or circuit system according to the invention are applicable accordingly to the magnetic resonance imaging apparatus according to the invention and vice versa. Attached Figure Description

[0039] Other advantages and details of the invention will become apparent from the embodiments described below and from the accompanying drawings. These are shown herein:

[0040] Figure 1 illustrates an embodiment of a transformer according to the present invention;

[0041] Figure 2 shows an embodiment of a single winding for the second coil of a transformer;

[0042] Figure 3 shows a side view of an embodiment of the transformer;

[0043] Figure 4 shows a perspective view of the transformer winding support; and

[0044] Figure 5 illustrates an embodiment of a magnetic resonance imaging apparatus according to the invention, having one embodiment of the circuit system according to the invention. Detailed Implementation

[0045] Figure 1 illustrates an embodiment of a transformer 1 according to the present invention. The transformer 1 includes a first coil 2 and two second coils 3 and 4. The first coil 2 includes a plurality of winding groups 5 connected in series, wherein each winding group 5 includes a plurality of windings 6 of the first coil 2. The first second coil 3 includes a plurality of individual windings 7, which are connected in parallel. Correspondingly, the second second coil 4 includes a plurality of individual windings 8, which are also connected in parallel. Therefore, the second coils 3 and 4 respectively include windings formed by a plurality of individual windings 7 or 8 connected in parallel.

[0046] Furthermore, the transformer 1 includes a core 9 extending along a longitudinal axis 10. The core 9 may be made of, for example, a ferrite polymer material. Winding groups 5 of the first coil 2 and individual windings 7 and 8 of the second coils 3 and 4 are arranged along the longitudinal axis 10 at the core 9. Here, the winding groups 5 and individual windings 7 and 8 are alternately arranged at the core 9 in the longitudinal direction. Here, multiple winding groups 5 are respectively arranged between two individual windings 7 and 8, or multiple individual windings 7 and 8 are respectively arranged between two winding groups 5. Here, the first coil 2 includes six winding groups 5, each having eighteen windings 6, such that the first coil 2 has a total of 108 windings. The second coils 3 and 4 each include seven individual windings 7 and 8, resulting in a winding ratio of 108:1 between the first coil 2 and each of the second coils 3 and 4.

[0047] The individual windings 7 and 8 of the second coils 3 and 4 are arranged in a single winding group 11 at the core 9. Here, the single winding group 11, including one individual winding 7 and 8 of the second coils 3 and 4, is arranged adjacently at the winding group 5 or between the two winding groups 5 of the first coil 2. The individual windings 7 and 8 of the second coils 3 and 4 are at least partially insulated from each other.

[0048] The winding groups 5 of the first coil 2 are respectively disposed in insulated winding carriers 12, which insulate the windings 6 of the winding groups 5 relative to the adjacent individual winding groups 11 or corresponding individual windings 7, 8 of the second coils 3, 4 and relative to the core 9. An encapsulating material 19 may be provided between the core 9 and the winding groups 5 or individual windings 7, 8. A low leakage inductance of the transformer 1 is achieved by alternately stacking the individual windings 7, 8 and winding groups 5 longitudinally at the core 9, because the field distribution between the first coil 2 and the second coils 3, 4 is at least substantially the same.

[0049] The thickness of individual windings 7 and 8, i.e., the extension of individual windings 7 and 8 along the longitudinal axis 10, is chosen such that they are not penetrated by the alternating field applied at the second coils 3 and 4. The thickness of individual windings 7 and 8 is particularly chosen to be greater than twice the skin penetration depth of the alternating field at the second coils 3 and 4. Flux guidance through the core 9 of transformer 1 is achieved in this way.

[0050] Furthermore, by dividing the second coils 3 and 4 into individual windings 7 and 8 connected in parallel, the conductor cross-sections of the second coils 3 and 4 are minimized while maximizing the surface area. This reduces the material required to manufacture the transformer 1 and reduces the space requirements of the transformer 1. Moreover, ohmic losses in the transformer 1 can be reduced when the transformer 1 operates at high switching frequencies or when high-frequency alternating current is fed into the transformer 1. Furthermore, a high volume-dependent power density of the transformer 1 is obtained.

[0051] Figure 2 shows an embodiment of a single winding 7, 8 of the second coils 3, 4. The single windings 7, 8 are each formed by a planar winding element 13. The winding element 13 includes a disc-shaped section 14 surrounding a circular opening 15. The opening 15 allows the winding element 13 to be positioned at the partially cylindrical core 9 of the transformer 1. Furthermore, the winding element 13 includes a first contact section 16 and a second contact section 17. The second contact section 17 is angled to the first contact section 16 in a drawing plane corresponding to a plane orthogonal to the longitudinal axis 10.

[0052] As shown in the side view of transformer 1 in Figure 3, a single winding group 11 can be formed by means of two single windings 7 and 8, such that the planar winding elements 13 forming the single windings 7 and 8 are arranged at the core 9 with opposite orientations. This allows the two single windings 7 and 8 to be connected via contact segments 16, and second contact segments 17 to be used to contact either the single windings 7 and 8 or the second coils 3 and 4. In this way, for example, a series connection of the second coils 3 and 4 can be achieved, wherein the first contact segments 16 are respectively center taps between the two second coils 3 and 4.

[0053] In order to connect the winding groups 5, that is, to form a series connection of the winding groups 5 to form the first coil 2, two adjacent winding groups 5 can be connected in section 18 respectively. Section 18 can be encapsulated, for example, by means of encapsulating material 19.

[0054] Individual windings 7 and 8 can be made into stamped parts, for example, from conductive sheet metal and conductive film. Here, for example, sheet metal and / or film made of copper can be used. Particularly in the region of the annular section 14, the sheet metal or film can have insulating portions to insulate the second coils 3 and 4 relative to each other in this region. The winding elements can, for example, have a thickness between 0.1 mm and 5 mm, particularly between 0.5 mm and 2 mm, and preferably 1 mm, along the longitudinal axis.

[0055] As shown in Figure 1, the contact segments 16 are connected to the connecting elements 20. The connecting elements 20 are bolts made of a conductive material, such as bronze, and are guided through the openings of the contact segments 16 of the winding elements 13 that form the individual windings 7 and 8 of coils 3 and 4. Spacer elements 21 are provided between the contact segments 16 of two adjacent groups of individual windings 11 to ensure stable fixation of the contact segments 16 at the connecting elements 20. The spacer elements 21 can be made of a conductive material, such as galvanized bronze. With the aid of the connecting elements 20, the transformer 1 can be fixed to a third object 22, such as a busbar. Here, the core 9 of the transformer 1 is free to oscillate because the entire transformer 1 is supported by the individual windings 7 and 8 and the connecting elements 20.

[0056] Figure 4 shows a perspective view of the winding support 12, in which the winding group 5 is housed. The winding support 12 includes a hollow cylindrical section 23 and two annular disc-shaped sections 24, each disposed at an end of the hollow cylindrical section 23. The winding support 12 may be constructed from one or more plastic components, wherein at least one annular disc-shaped section 24 may be configured as a separate element.

[0057] The annular disc-shaped section 24 has a thickness between 0.1 mm and 1 mm, for example, 0.4 mm, along the longitudinal axis 10. The wall thickness of the hollow cylindrical section 23 from the core 9 can also be between 0.1 mm and 1 cm, for example, 0.4 mm, so that the winding group 5 wound between the annular disc-shaped sections 24 and the outer circumference of the hollow cylindrical section 23 achieves uniform insulation with the adjacent individual windings 7, 8 and the core 9.

[0058] Figure 5 illustrates one embodiment of a magnetic resonance imaging (MRI) apparatus 25. The MRI apparatus 25 includes a circuit system 26 comprising a current source 27 and a transformer 1. The circuit system 26 is used, for example, to energize the magnets of the MRI apparatus 25. For this purpose, the transformer 1 may be connected to the magnets 28 via additional circuit components 29 to generate a direct current for energizing the magnets 28.

[0059] The current source 27 is connected to the first coil 2 of the transformer 1. The second coils 3 and 4 are connected to the magnet 28 via an additional circuit component 29 if necessary. The transformer 1 can generate a high output current from the current source 27 to energize the magnet 28.

[0060] Coils 3 and 4 can be tapped via second contact segments 17 of winding elements 13 forming individual windings 7 and 8, respectively. First contact segments 16, connected via connecting elements 20, can serve as center taps for the two second coils 3 and 4. The planar winding elements 13 of the second coils 3 and 4 have a thickness along the longitudinal axis 10, which is greater than twice the penetration depth of the alternating field at the second coils 3 and 4 due to the current feed into the first coil 2.

[0061] Although the details of the invention have been described and illustrated in detail with reference to preferred embodiments, the invention is not limited to these disclosed examples and other variations can be derived by those skilled in the art without departing from the scope of protection of the invention.

Claims

1. A transformer comprising a first coil (2) and at least one second coil (3, 4), the first coil and the second coil respectively surrounding a circumference of a common core (9) extending along a longitudinal axis (10), wherein the first coil (2) comprises a plurality of winding groups (5) connected in series, each consisting of a plurality of windings (6), and the second coil (3, 4) comprises a plurality of individual windings (7, 8) connected in parallel, wherein at least one of the plurality of winding groups (5) is disposed between two individual windings of the plurality of individual windings (7, 8) and / or at least one individual winding of the plurality of individual windings (7, 8) is disposed between two winding groups of the plurality of winding groups (5) along the longitudinal axis (10) at the core (9), characterized in that, The winding group (5) and the individual windings (7, 8) are alternately arranged along the longitudinal axis (10) at the core (9), wherein a plurality of the individual windings (7, 8) are each formed by planar winding elements (13), the thickness of the winding elements along the longitudinal axis (10) being greater than twice the penetration depth of the alternating field generated by the alternating current of the first coil (2) at the second coil (3, 4), wherein the winding element (13) has a first contact segment (16) and a second contact segment (17), wherein the first contact segment (16) and the second contact segment (17) extend outward away from the core (9), and wherein the second contact segment (17) extends at an angle to the first contact segment (16) in a drawing plane corresponding to a plane orthogonal to the longitudinal axis (10), and wherein the winding element (13) is made of conductive sheet metal and / or conductive thin film.

2. The transformer according to claim 1, characterized in that, The transformer (1) includes a plurality of second coils (3, 4), wherein adjacent individual windings (7, 8) of the second coils (3, 4) are arranged at the core (8) in at least one individual winding group (11), wherein each individual winding group (11) includes a single winding (7, 8) of the second coils (3, 4).

3. The transformer according to claim 1 or 2, characterized in that, Multiple winding groups (5) are respectively disposed at an insulated winding carrier (12), wherein the winding carrier (12) insulates the winding groups (5) relative to the core (9) and relative to the adjacent multiple individual windings (7, 8).

4. The transformer according to claim 1 or 2, characterized in that, The first coil (2) comprises a total of between 50 and 200 windings.

5. The transformer according to claim 1 or 2, characterized in that, The winding element (13) has a thickness between 0.1 mm and 5 mm along the direction of the longitudinal axis (10).

6. The transformer according to claim 1 or 2, characterized in that, The first contact segments (16) of the plurality of winding elements (13) are respectively connected to a common connecting element (20) extending along the longitudinal axis.

7. The transformer according to claim 6, characterized in that, The transformer can be fixed via the connecting element (20), wherein the core (9) is held at the second coil (3, 4) with free oscillation.

8. The transformer according to claim 1 or 2, characterized in that, The core (9), the first coil (2) and / or the second coil (3, 4) are at least partially encapsulated by means of encapsulating material (19).

9. A circuit system comprising a current source (27) and a transformer (1) according to any one of claims 1 to 8.

10. The circuit system according to claim 9, characterized in that, The current source (27) is connected to the first coil (2) of the transformer (1) and can input AC current into the first coil (2) through the current source (27).

11. A magnetic resonance imaging apparatus comprising a transformer (1) according to any one of claims 1 to 8 or a circuit system (25) according to claim 9 or 10.

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