CN114512316A

CN114512316A - Transformer, circuit system and magnetic resonance imaging device

Info

Publication number: CN114512316A
Application number: CN202111360773.7A
Authority: CN
Inventors: 沃尔克·莫德尔
Original assignee: Siemens Healthineers AG
Current assignee: Siemens Medical Ag
Priority date: 2020-11-17
Filing date: 2021-11-17
Publication date: 2022-05-17
Also published as: DE102020214444A1

Abstract

A transformer comprising a first coil (2) and at least one second coil (3, 4) each enclosing a circumference of a common core (9) extending 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 at the core (9) along the longitudinal axis (10) the winding group (5) or at least one of the winding groups (5) is arranged between two individual windings (7, 8) and/or the individual windings (7, 8) or at least one of the individual windings (7, 8) is arranged between two winding groups (5).

Description

Transformer, circuit system and magnetic resonance imaging device

Technical Field

The invention relates to a transformer comprising a first coil and at least one second coil, each of which surrounds a circumference of a common core extending along a longitudinal axis. Furthermore, the invention relates to a circuit system and a magnetic resonance imaging apparatus.

Background

In many applications, it is desirable to operate the transformer at a high switching frequency, by means of which, for example, the space requirement of the transformer can be minimized and/or by means of which a cost-effective production of the transformer and/or of the circuit system comprising the transformer can be achieved. Such applications are found, for example, in transformers used in switching power supplies.

However, at high switching frequencies, conduction of alternating current at the surface of the coil of the transformer occurs due to the skin effect, so that the cross section of the wire used to form the coil is limited by the skin penetration depth. The use of electrical lines with a large cross section, such as rf strands, for example, has the disadvantage that it is not possible to ensure that the inner core of the strand is contacted at the end of the coil formed from the strands, since, for example, when contacting by means of cable lugs or by means of a welded and/or clamped connection, only the outer strand is contacted, so that current guidance in the interior of the strand cannot be achieved or at least cannot be achieved reliably.

In addition to the skin effect, the use of transformers at high switching frequencies can also be limited by the leakage inductance of the transformer. Particularly in the case of high transformation ratios of the transformer, the leakage inductance is very important as a parasitic effect, since it counteracts the transmission of high currents in the transformer at high switching frequencies.

Disclosure of Invention

The object on which the invention is based is therefore to provide an improved transformer which can be used, in particular, at high switching frequencies and/or high currents.

In order to achieve the object, according to the invention in a transformer of the type mentioned at the outset, the first coil is one or more winding groups connected in series and the second coil comprises one or more individual windings connected in parallel, wherein the winding group or at least one of the winding groups is arranged between two individual windings and/or at least one of the individual windings is arranged between two winding groups along the longitudinal axis at the core.

The first coil is formed of one or more winding groups connected in series. The second coil comprises one or more individual windings connected in parallel such that a high transformation ratio for transmission from the first coil to the second coil is generated. By geometrically arranging the first coil and the second coil along the longitudinal axis of the core, a small leakage inductance between the first coil and the second coil is advantageously obtained. The arrangement of the coils also makes it possible to achieve a compact structural shape of the transformer.

This yields the advantage that no additional capacitor is required to compensate for the leakage inductance. Furthermore, the transformer can be operated at a high frequency due to the arrangement of the first coil and the second coil and generates a high output current, in particular when the first coil is used as a primary coil and the second coil is used as a secondary coil.

Compared to conventional transformers which, for example, operate at a lower frequency than resonant converters, a lower-cost production of the transformer or of the circuit arrangement comprising the transformer is advantageously achieved, since additional components, such as capacitors for compensating for leakage inductances, can be dispensed with. In addition to this, the space requirement of the transformer is also reduced, which is particularly advantageous for a circuit system comprising the transformer.

The arrangement of the individual windings between two winding groups or the arrangement of a winding group between two individual windings makes it possible to achieve a high surface overlap of up to 100% between the windings of the first coil and the second coil. By advantageously arranging the winding groups of the first coil and the individual windings of the second coil at the core, it is achieved that the field distribution between the first coil and the second coil is at least substantially identical. This causes a small leakage inductance when coupling the first coil and the second coil.

The high surface overlap is achieved by: that is to say one or more winding groups of the first coil and one or more individual windings of the second coil are arranged offset along the longitudinal axis at the core and thus each surround the same surface corresponding to the cross-sectional shape of the core, wherein the surfaces overlap when viewed in the longitudinal direction. Additionally, the face overlap may also be improved by: i.e. the individual windings are at least substantially congruent with the winding groups, so that a surface overlap between the coils themselves can also be achieved.

For this purpose, the individual windings of the second coil can be formed in a planar manner in order to achieve an overlap with a winding group, which comprises a plurality of windings made of electrically conductive metal wires, for example. The spread of the planar individual windings in the direction perpendicular to the longitudinal axis may correspond in particular to the spread of at least one adjacent winding group in the direction perpendicular to the longitudinal axis. In particular, the extent of all individual windings and all winding groups of the transformer in a direction orthogonal to the longitudinal axis is identical or at least substantially identical.

The core may be formed by one or more core elements which are arranged in particular directly next to one another. In particular, along the longitudinal axis, the core may have a cylindrical or square shape at least in sections, so that the first coil and the at least one second coil can be arranged around the core along the longitudinal axis.

According to the invention, it can be provided that the first coil comprises a plurality of winding groups connected in series and the second coil comprises a plurality of individual windings connected in parallel, wherein the winding groups and the individual windings are arranged alternately along the longitudinal axis at the core. In particular, it can be provided here that the number of individual windings of the second coil differs by one from the number of winding groups of the first coil, so that an alternating arrangement of winding groups and individual windings along the longitudinal axis of the core is possible. In this case, a row of alternately arranged individual windings and winding groups can each have an individual winding or a winding group depending on which number is greater at the outer end.

It is possible that the first coil comprises between four and ten, in particular six, winding groups and the second coil comprises between four and ten, in particular seven, individual windings connected in parallel. In the case of six winding groups of the first coil and seven individual windings of the second coil, the individual windings of the winding groups can be arranged alternately along the core, for example, starting with the individual windings of the second coil when manufacturing the transformer. However, other numbers of winding groups and/or first coils may be used depending on the requirements of the transformer.

In a preferred embodiment of the invention, it can be provided that the transformer comprises a plurality of second coils, wherein the individual windings of the second coils are arranged adjacent to one another in pairs at the core in at least one individual winding group each comprising an individual winding of the second coils. In order to be able to achieve as low a leakage inductance as possible of the transformer even in the case of a plurality of second coils by means of as identical a field distribution as possible between the first coil and the second coil, the individual windings of the second coils are each arranged as individual winding groups at the core. Here, a single winding group may be provided between two winding groups of the first coil or a winding group of the first coil may be provided between two single winding groups. The individual windings of the second coil are insulated at least in some areas with respect to one another in order to achieve an electrical separation of the second coil.

In particular, the second coils may each have the same number of individual windings connected in parallel, so that all individual windings of the second coils may be arranged as individual winding groups at the core of the transformer. For example, it is possible for the transformer to comprise two second coils, each having one or more individual windings connected in parallel. In this case, the second coils can be connected in series with one another when the second coils are used as secondary coils or as output terminals of a transformer, so that the half-waves of the alternating current transmitted via the transformer can be intercepted at each of the two second coils.

According to the invention, it can be provided that one or more winding groups are each arranged on an insulated winding carrier, wherein the winding carrier insulates the winding group relative to the core and relative to the adjacent individual winding or windings. In an at least partially cylindrically formed core of the transformer, the winding support can be formed, for example, as a sleeve having a ring arranged on the end face at the sleeve. The winding groups provided on the winding support can be wound on the outer circumference of the sleeve and are surrounded on the end by a ring.

The winding support is made of an electrically insulating material, so that the winding groups can be arranged on the winding support between the rings arranged on the end sides, in order to be able to insulate the winding groups from the core and/or from at least one adjacent individual winding. The winding support can be made of plastic, for example, and has a thickness of between 0.1mm and 1mm, in particular 0.4 mm. Other insulation thicknesses may also be selected in relation to the power to be converted by the transformer or by the voltage applied on the first coil and/or the at least one second coil.

In a preferred embodiment of the invention, it can be provided that the one or more winding groups of the first coil comprise a total of between 50 and 200, in particular between 60 and 80, windings. The windings of the first coil are in particular divided into a plurality of winding groups, wherein the number of windings per winding group corresponds in particular to the total number of windings of the first coil divided by the number of winding groups. For example, the first coil having 66 windings may be divided into six winding groups each having eleven coils. It is also possible here to select the number of windings and/or the division of the windings into winding groups depending on the intended use of the transformer.

According to the invention, it can be provided that one or more individual windings are each formed from a planar winding element. The winding element may be at least partially annular disk-shaped in order to form a winding. The width of the annular disk-shaped region can in particular correspond to the width of the winding groups, so that a surface overlap between the annular disk-shaped section and one or more winding groups can be achieved.

The winding element may have an opening in which a core of the transformer may be arranged. The shape of the opening may here correspond to the shape of the cross section of the core at which the individual windings and winding groups are arranged. In addition to the annular disk-shaped winding portion, the winding element can additionally have one or more contact portions, as is explained in more detail below.

The formation of the individual windings as planar winding elements results in a large surface area of the individual windings, which is compatible with the operation of the transformer at high frequencies due to the skin effect that occurs. At the same time, the formation of the individual windings by planar winding elements makes it possible to achieve a minimized power cross section, so that the material required overall for forming the at least one coil can be advantageously reduced. In this way, a minimum power cross section results with a high surface of the second coil. This advantageously results in too low an ohmic loss, for example in the case of high switching frequencies of the transformer, which occurs when the transformer is used in a switching power supply, or in the case of high-frequency alternating currents. Furthermore, the material used for forming the second coil is reduced, so that a high volume-dependent power density of the transformer can advantageously be achieved.

According to the invention, it can be provided for the winding element to be produced from an electrically conductive sheet metal and/or an electrically conductive film, in particular as a stamped part. In particular, in a transformer with more than one second winding, the winding element can have an insulation at least in the region of the winding section of the winding element arranged on the core in order to electrically insulate two winding elements of two different second coils arranged next to one another from one another. The production of the winding element as a stamped part from an electrically conductive sheet metal and/or an electrically conductive film makes possible a simple and cost-effective production of the transformer.

The winding element can be formed, for example, from a copper sheet metal and/or a copper film. The thickness of the winding element, i.e. the extent of the winding element in the direction of the longitudinal axis of the core, can in this case be selected in particular as a function of the frequency of the alternating current to be transmitted via the transformer or the switching frequency at which the transformer is operated. The thickness of the winding element can take into account the skin effect produced and is, for example, at least double the skin penetration depth. In this way, flux guidance through the core of the transformer is also achieved in the region of the second coil. According to the invention, it can be provided that the winding element has a thickness in the direction of the longitudinal axis of between 0.1mm and 5mm, in particular between 0.5mm and 2mm, preferably 1 mm.

In a preferred embodiment of the invention, it can be provided that the one or more winding elements each have two contact sections, wherein the contact sections each extend outwardly away from the core, wherein the contact sections of the one or more winding elements are each connected to a common connecting element extending along the longitudinal axis.

The winding elements forming the individual windings of the at least one second coil can be electrically connected to one another by means of the contact sections. In particular, in the case of two second coils, the contact sections of the winding elements of the two coils can also be connected to a common connecting element extending along the longitudinal axis, so that the two second coils can be electrically contacted via the connecting element. The connecting element can thereby bring about an electrical contact and/or a mechanical fixing of the winding element via corresponding contact sections connected to the connecting element.

According to the invention, it can be provided that the transformer can be fixed via the connecting element, wherein the core is held freely oscillating at the second coil. The transformer can be fixed, for example, to the busbar via a connecting element. The connecting element can be designed, for example, as a bolt made of an electrically conductive metal, for example copper or brass. Between the two individual windings of the winding group between which the first coil is arranged or between the contact sections of the individual winding groups, a spacer element can be arranged in each case, the thickness of which spacer element corresponds in particular to the thickness of the winding group, so that a stable connection of the contact sections to the connecting element can be achieved. The spacer element can be made of an electrically conductive metal, for example, so that a mechanically stable and electrically conductive fixing of the contact section via the connecting element can be achieved. The spacer element can be made of an electrically conductive metal, for example, galvanized copper or the like.

In the case of a fastening of the transformer via the connecting element, it is possible for the transformer to be carried by a single winding of the second coil, which winding is formed as a winding element. This makes it possible to arrange the core of the transformer in a freely oscillating manner. This placeability of the transformer is advantageously achieved in that the core, which can be subjected to electromagnetic forces, can oscillate at least to a certain extent, so that damage to the core and/or to the transformer can advantageously be avoided.

According to the invention, it can be provided that the further contact section of the winding element extends at an angle to the contact section of the winding element, which is connected to the connecting element, in a plane orthogonal to the longitudinal axis. The winding elements of the second coil each extend in a plane orthogonal to the longitudinal axis of the core. In the case of a planar winding element, the two contact sections each extend in a plane perpendicular to the longitudinal axis of the core.

When one of the contact sections is connected to the connecting element, the other contact section may extend at an angle to the contact section connected to the connecting element, so that a lateral contact of the contact section and thus of the individual windings can be achieved. Advantageously, in this arrangement it can be achieved that, when the two second coils are arranged at the transformer, identically shaped winding elements can be used for the individual windings of the two second coils, respectively, if the winding elements are arranged at the core in different orientations, respectively. In this way, it is possible to angle the further contact sections on different sides in each case with respect to the contact sections of the individual windings which are connected to the common connecting element. Thereby, the second coils may be laterally contacted separately from each other, respectively. Furthermore, the manufacture of the transformer is simplified by using identically shaped winding elements.

According to the invention, it can be provided that the core is made of a ferrite material, in particular a ferrite polymer material. The core may be cylindrical or square at least in sections, for example, so that the winding groups and the individual windings can be arranged at the core. The core may be composed of one or more elements, wherein the core composed of a plurality of elements may for example be combined into a closed yoke or the like, so that a guiding of the magnetic flux in the transformer may be achieved.

In a preferred embodiment of the invention, it can be provided that the core, the first coil and/or the second coil are at least partially encapsulated with an encapsulation material. This protects the transformer from external influences and from core and coil damage.

It is proposed for the circuit arrangement according to the invention to comprise a current source and a transformer according to the invention. The current source is in particular connected to one of the coils of the transformer. In order to generate a current with a high current strength and a low voltage, the current source may be connected in particular to a first coil as a primary coil, wherein an output current with a high current strength may be generated at a second coil as a secondary coil, if the ratio of the number of turns of the first coil to the number of turns of the second coil is large.

In a preferred embodiment of the invention, it can be provided that a current source is connected to the first coil of the transformer and via which an alternating current can be fed into the first coil, wherein one or more individual windings are each formed from a planar winding element, the thickness of which in the direction of the longitudinal axis is greater than the double penetration depth of the alternating field generated by the first coil on the basis of the alternating current at the second coil. The penetration depth is thereby generated by the skin effect of the alternating current conducted at the second coil. The thickness of the coil can in particular have a value between double and ten times the penetration depth. In this way, flux guidance through the core of the transformer is also achieved in the region of the second coil.

All the advantages and embodiments described above with respect to the transformer according to the invention apply accordingly also to the circuit system and vice versa.

It is proposed for the magnetic resonance imaging apparatus according to the invention that the magnetic resonance imaging apparatus comprises at least one transformer according to the invention and/or at least one circuit system according to the invention. A transformer or circuitry including a transformer may be used herein to supply current to one or more magnets of a magnetic resonance imaging apparatus. The generation of high currents via the transformer may advantageously be used to use a magnetizing current for magnetization or to form a field in one or more magnets of the magnetic resonance imaging apparatus. The compact design of the transformer can be advantageously achieved in that the core and the coil of the transformer are formed using relatively little material. In this way, disturbing influences on the imaging by a transformer arranged in the vicinity of the magnet of the magnetic resonance imaging device can be avoided or at least reduced.

All the advantages and embodiments described above with regard to the transformer according to the invention or the circuit arrangement according to the invention apply accordingly to the magnetic resonance imaging apparatus according to the invention and vice versa.

Drawings

Further advantages and details of the invention emerge from the examples of embodiment described below and from the figures. Shown here are:

fig. 1 shows an embodiment of a transformer according to the invention;

FIG. 2 illustrates one embodiment of a single winding for a second coil of a transformer;

FIG. 3 shows a side view of an embodiment of a transformer;

fig. 4 shows a perspective view of a winding carrier of a transformer; and

fig. 5 shows an embodiment of a magnetic resonance imaging apparatus according to the invention with an embodiment of the circuitry according to the invention.

Detailed Description

Fig. 1 shows an exemplary embodiment of a transformer 1 according to the present invention. The transformer 1 comprises a first winding 2 and two second windings 3, 4. The first coil 2 comprises a plurality of series-connected winding groups 5, wherein each winding group 5 comprises a plurality of windings 6 of the first coil 2. The first second coil 3 comprises a plurality of individual windings 7, which are each connected in parallel. Correspondingly, the second coil 4 comprises a plurality of individual windings 8, which are likewise connected in parallel. The second coils 3, 4 each therefore comprise a winding which is formed from a plurality of individual windings 7 or 8, respectively, which are connected in parallel.

Furthermore, the transformer 1 comprises a core 9, which extends along a longitudinal axis 10. The core 9 may for example be made of a ferrite polymer material. The winding group 5 of the first coil 2 and the individual windings 7, 8 of the second coils 3, 4 are arranged along the longitudinal axis 10 at the core 9. The winding groups 5 and the individual windings 7, 8 are arranged alternately in the longitudinal direction on the core 9. In this case, a plurality of winding groups 5 are each arranged between two individual windings 7, 8 or a plurality of individual windings 7, 8 are each arranged between two winding groups 5. The first coil 2 comprises six winding groups 5, each having eighteen windings 6, so that the first coil 2 has a total of 108 windings. The second coils 3, 4 each comprise seven individual windings 7, 8, so that a winding ratio of 108:1 results for the first coil 2 and each second coil 3, 4.

The individual windings 7, 8 of the second coils 3, 4 are arranged at the core 9 in individual winding groups 11. In this case, the individual winding groups 11, which each comprise one individual winding 7, 8 of the second coils 3, 4, are arranged adjacent to one another in each case at the winding group 5 or between two winding groups 5 of the first coil 2. The individual windings 7, 8 of the second coils 3, 4 are insulated at least in regions in this case with respect to one another.

The winding groups 5 of the first coil 2 are each arranged in an insulated winding carrier 12, which insulates the windings 6 of the winding groups 5 from adjacent individual winding groups 11 or from the respective individual windings 7, 8 of the second coils 3, 4 and from the core 9. An encapsulation material 19 may be provided between the core 9 and the winding groups 5 or the individual windings 7, 8. By alternately stacking the individual windings 7, 8 and the winding groups 5 at the core 9 in the longitudinal direction, a low leakage inductance of the transformer 1 is achieved, since the field distribution between the first coil 2 and the second coils 3, 4, respectively, is at least substantially identical.

The thickness of the individual windings 7, 8, i.e. the extent of the individual windings 7, 8 in the direction of the longitudinal axis 10, is selected in such a way that it is not penetrated by the alternating field applied at the second coils 3, 4. The thickness of the individual windings 7, 8 is selected here in particular to be greater than the double skin penetration depth of the alternating field at the second coils 3, 4. In this way, flux guidance through the interior of the core 9 of the transformer 1 is achieved.

Furthermore, by dividing the second coils 3, 4 into individual windings 7, 8, which are each connected in parallel, the largest possible surface is achieved while the conductor cross section of the second coils 3, 4 is minimized. This reduces the material required for manufacturing the transformer 1 and reduces the space requirement of the transformer 1. Furthermore, in the case of high switching frequencies at which the transformer 1 is operated, or in the case of high-frequency alternating currents fed into the transformer 1, the ohmic losses in the transformer 1 can be reduced. Furthermore, a high volume-dependent power density of the transformer 1 results.

Fig. 2 shows an exemplary embodiment of a single winding 7, 8 of the second coil 3, 4. The individual windings 7, 8 are each formed by a planar winding element 13. The winding element 13 comprises a disk-shaped section 14, which in this case surrounds a circular opening 15. The winding element 13 can be arranged at the partially cylindrical core 9 of the transformer 1 by means of the opening 15. Furthermore, the winding element 13 comprises 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.

As is shown in fig. 3 in a side view of the transformer 1, the individual winding groups 11 can be formed by means of the two individual windings 7, 8 in such a way that the planar winding elements 13 forming the individual windings 7, 8 are arranged in opposite orientations on the core 9. This makes it possible for the two individual windings 7, 8 to be connected in each case via a contact section 16, while a second contact section 17 can be used to contact the individual windings 7, 8 or the second coils 3, 4 in each case. In this way, for example, a series connection of the second coils 3, 4 can be achieved, wherein the first contact section 16 is in each case an intermediate tap between the two second coils 3, 4.

In order to connect the winding groups 5, i.e. 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 each case in a section 18. The sections 18 can be encapsulated, for example, by means of an encapsulating material 19.

The individual windings 7, 8 can be produced, for example, as stamped parts from electrically conductive sheet metal and electrically conductive film. For example, sheet metal and/or films made of copper can be used here. In particular in the region of the annular section 14, the sheet metal or the film can have an insulation in order to insulate the second coils 3, 4 from one another in this region. The winding element may have a thickness of between 0.1mm and 5mm, in particular between 0.5mm and 2mm, preferably 1mm, in the direction of the longitudinal axis, for example.

As shown in fig. 1, the contact sections 16 are each connected to a connecting element 20. The connecting elements 20 are formed here as bolts from an electrically conductive material, for example from bronze, and are each guided through an opening of the contact section 16 of the winding element 13 forming the individual windings 7, 8 of the coils 3, 4. Spacer elements 21 are respectively arranged between the contact portions 16 of two adjacent individual winding groups 11 in order to be able to achieve a stable fixing of the contact portions 16 at the connecting element 20. The spacer element 21 can be made of an electrically conductive material, for example, galvanized bronze. By means of the connecting element 20, the transformer 1 can be fixed to a third object 22, for example to a busbar or the like. The core 9 of the transformer 1 is free-running, since the entire transformer 1 is supported via the individual windings 7, 8 and the connecting element 20.

Fig. 4 shows a perspective view of the winding carrier 12, in which the winding groups 5 are accommodated. The winding carrier 12 comprises a hollow cylindrical section 23 and two annular disc-shaped sections 24, which are each arranged at an end of the hollow cylindrical section 23. The winding carrier 11 can be formed, for example, from one or more plastic parts, wherein in particular at least one annular disk-shaped section 24 can be formed as a separate element.

The annular disk-shaped section 24 has a thickness in the direction of the longitudinal axis 10 of between 0.1mm and 1mm, for example 0.4 mm. The wall thickness of the hollow-cylindrical section 23 from the core 9 can also be between 0.1mm and 1cm, for example 0.4mm, so that a uniform insulation of the winding groups 5 wound onto the outer circumference of the hollow-cylindrical section 23 between the annular disc-shaped sections 24 from the adjacent individual windings 7, 8 and from the core 9 is achieved.

An embodiment of a magnetic resonance imaging apparatus 25 is shown in fig. 5. The magnetic resonance imaging apparatus 25 comprises circuitry 26 comprising a current source 27 and a transformer 1. The circuitry 26 is for example used to energize a magnet of the magnetic resonance imaging apparatus 25. For this purpose, the transformer 1 can be connected to the magnet 28 via a further circuit component 29 in order to generate a direct current for energizing the magnet 28.

The current source 27 is connected to the first winding 2 of the transformer 1. The second coils 3, 4 are connected to the magnet 28, if necessary, via a further circuit component 29. A high output current can be generated from the current emitted by the current source 27 by means of the transformer 1 in order to energize the magnet 28.

The coils 3, 4 can be tapped via the second contact sections 17 of the winding elements 13 forming the individual windings 7, 8, respectively. The first contact section 16 connected via the connecting element 20 can be used as an intermediate tap for the two second coils 3, 4. The planar winding elements 13 of the second coils 3, 4 each have a thickness in the direction of the longitudinal axis 10, which is greater than double the penetration depth of the alternating field at the second coils 3, 4, which is generated as a result of the current feed into the first coil 2.

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

Claims

1. A transformer comprising a first coil (2) and at least one second coil (3, 4) each enclosing a circumference of a common core (9) extending along a longitudinal axis (10), wherein the first coil (2) comprises 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 at the core (9) along the longitudinal axis (10) the winding group (5) or at least one of the winding groups (5) is/are arranged between two of the individual windings (7, 8) and/or the individual winding (7, 8) or the individual windings (7, 7), 8) Is arranged between two of said winding groups (5).

2. The transformer according to claim 1, wherein the transformer is a transformer,

it is characterized in that the preparation method is characterized in that,

the first coil (2) comprises a plurality of series-connected winding groups (5) and the second coil (3, 4) comprises a plurality of parallel-connected individual windings (7, 8), wherein the winding groups (5) and the individual windings (7, 8) are alternately arranged along the longitudinal axis (10) at the core (9).

3. The transformer according to claim 1 or 2,

it is characterized in that the preparation method is characterized in that,

the transformer (1) comprises a plurality of second coils (3, 4), wherein the individual windings (7, 8) of the second coils (3, 4) are arranged in pairs adjacent to each other at the core (8) in at least one individual winding group (11) each comprising an individual winding (7, 8) of the second coils (3, 4).

4. The transformer of any one of the preceding claims,

it is characterized in that the preparation method is characterized in that,

one of the winding groups (5) or a plurality of the winding groups (5) is/are each arranged on an insulated winding carrier (12), wherein the winding carrier (12) insulates the winding group (5) relative to the core (9) and relative to an adjacent one of the individual windings (7, 8) or a plurality of the individual windings (7, 8).

5. The transformer of any one of the preceding claims,

it is characterized in that the preparation method is characterized in that,

the winding group (5) or the winding groups (5) of the first coil (2) comprise between 50 and 200 windings in total.

6. The transformer of any one of the preceding claims,

it is characterized in that the preparation method is characterized in that,

the individual winding (7, 8) or the individual windings (7, 8) are each formed by a planar winding element (13).

7. The transformer according to claim 6, wherein the transformer is a transformer,

it is characterized in that the preparation method is characterized in that,

the winding element (13) is made of an electrically conductive sheet metal and/or an electrically conductive film.

8. The transformer according to claim 6 or 7,

it is characterized in that the preparation method is characterized in that,

the winding element (13) has a thickness in the direction of the longitudinal axis (10) of between 0.1mm and 5 mm.

9. The transformer according to any one of claims 6 to 8,

it is characterized in that the preparation method is characterized in that,

the winding element (13) or the winding elements (13) each have two contact sections (16, 17), wherein the contact sections (16, 17) each extend outwardly away from the core (9), wherein the contact sections of the winding element (13) or the winding elements (13) are each connected to a common connecting element (20) extending along the longitudinal axis.

10. The transformer according to claim 9, wherein the transformer is a transformer,

it is characterized in that the preparation method is characterized in that,

the transformer can be fixed via the connecting element (20), wherein the core (9) is held freely oscillating at the second coil (3, 4).

11. The transformer according to claim 9 or 10,

it is characterized in that the preparation method is characterized in that,

the further contact section (17) of the winding element (13) extends at an angle to the contact section (16) of the winding element (13) connected to the connecting element (20) in a plane orthogonal to the longitudinal axis (10).

12. The transformer of any one of the preceding claims,

it is characterized in that the preparation method is 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 an encapsulating material (19).

13. A circuit system comprising a current source (27) and a transformer (1) according to any of the preceding claims.

14. The circuit system according to claim 13, wherein,

it is characterized in that the preparation method is characterized in that,

the current source (27) is connected to a first coil (2) of the transformer (1) and by means of the current source (27) an alternating current can be fed into the first coil (2), wherein the individual winding (7, 8) or the individual windings (7, 8) are each formed by a planar winding element (13) whose thickness in the direction of the longitudinal axis (10) is greater than twice the penetration depth of an alternating field generated by the first coil (2) at the second coil (3, 4) as a result of the alternating current.

15. A magnetic resonance imaging apparatus comprising a transformer (1) according to any one of claims 1 to 12 and/or a circuit system (25) according to claim 13 or 14.