Tubular insulation of a primary coil of a contactless transformer of a separately excited synchronous machine

Abstract

The invention relates to a primary coil of a contactless transformer for a separately excited synchronous machine, comprising a ferrite core which is embodied in a hollow-cylindrical manner and has, on its radial outer side, a slot-like depression for receiving a winding; a winding which is arranged in the slot-like depression, having a radially inner lateral surface and a radially outer lateral surface; a first axial side and a second axial side which is located opposite the first axial side; a tubular insulation which is arranged on the inner radial lateral surface between the winding and the slot-like depression and encloses the winding on the first axial side and on the second axial side, wherein the tubular insulation forms a first portion which extends from the first axial side at least partially in an axial direction via the winding on the radially outer lateral surface, and the tubular insulation forms a second portion which extends from the second axial side at least partially in an axial direction via the winding on the radially outer lateral surface. The invention also relates to a contactless transformer, to a separately excited synchronous machine, and to a method for producing a primary coil of a contactless transformer for a separately excited synchronous machine.

Description

[0001] Tubular insulation of a primary coil of a contactless transformer of a separately excited synchronous machine

[0002] The present invention relates to a primary coil of a contactless transformer for a separately excited synchronous machine, comprising a ferrite core, a winding, a tubular insulation which is arranged on the inner radial surface between the winding and the groove-like recess.

[0003] The invention further relates to a contactless transformer, a separately excited synchronous machine, and a method for producing a primary coil of a contactless transformer for a separately excited synchronous machine.

[0004] Electric motors are increasingly being used for propulsion in motor vehicles to create alternatives to combustion engines that require fossil fuels. Considerable efforts have already been made to improve the everyday suitability of electric drives and also to offer users the same driving comfort they are accustomed to.

[0005] In addition to purely electric drivetrains, hybrid drivetrains are also known. Such drivetrains in hybrid vehicles typically comprise a combination of an internal combustion engine and an electric motor, enabling purely electric operation—for example, in urban areas—while maintaining sufficient range and availability, especially for long-distance journeys. Furthermore, in certain operating situations, it is possible to use both the internal combustion engine and the electric motor simultaneously.

[0006] In the development of electrical machines, particularly those intended for electric axles or hybrid modules, there is a continuing need to increase their power density and efficiency while simultaneously reducing manufacturing costs. In this context, it is also known to design electrical machines as separately excited synchronous machines (SMMs). In this case, the electrical power to excite the rotor windings must be transferred to the rotor of a separately excited synchronous machine. For traction machines, a contact-type transformer is generally used for this purpose. When these windings are energized, a magnetic field is created which, in combination with the stator's magnetic field, generates torque. The strength of the rotor field can be adjusted by changing the current supply. This allows the machine's behavior to be constantly adapted to the respective driving situation in an efficient manner.

[0007] The disadvantages of such a contact-based transformer are mechanical and electrical losses in the contact between stationary and rotating components. Further disadvantages include wear and tear of the components rubbing against each other, the resulting contamination from abrasion, and the comparatively large installation space requirement.

[0008] As an alternative to such contact-based transformers, contactless inductive transformers are also known. An inductive transformer is typically a rotationally symmetrical transformer with an air gap consisting of a primary and a secondary coil. Typically, an inductive transformer also has a core, for example, made of ferrite. Such a core can be made of one or more parts.

[0009] For example, all core parts can be attached to the stationary side of an electrical machine, with the secondary winding rotating within the core. Alternatively, core parts can be attached to the rotating part of the machine. In this case, the primary and secondary core parts are separated by an air gap. This gap must be large enough to ensure that the core parts do not touch, taking all tolerances and operating conditions into account. For this purpose, the rotating transformer parts are often provided with a bandage or integrated into another component to provide them with fixed speed support. An example of such a design variant can be found in DE 10 2017 214 776 A1 or DE201210201826 A1.

[0010] A contactless transformer, as used in separately excited synchronous machines, among other things, basically consists, like a transformer, of a primary part or primary coil and a secondary part or secondary winding. Using this design, an alternating current can be transmitted based on induction. Alternatively, the term inductive transformer can also be used. If, for example, a single-phase alternating current is applied to the primary part, a magnetic field is created in the winding of the primary coil, which also induces a single-phase alternating current in the winding of the secondary coil. The amount of the secondary voltage can be adjusted based on the number of turns of the winding on the primary part and secondary part as well as the primary voltage. The amount of the primary voltage and the number of turns vary depending on the application.In some cases, the primary voltage is significantly higher than the secondary voltage, which in turn requires more complex insulation.

[0011] Coil insulation is particularly important for high-voltage applications, such as those required for separately excited synchronous machines in the automotive industry. Inadequate insulation can lead to breakdowns or partial discharges within the system, which could result in system failure. A key aspect of coil insulation is layer insulation. Due to the voltage drop in the copper wire, the dielectric strength of the wire enamel may no longer be sufficient, requiring additional insulation between the wire layers. State-of-the-art conventional sheet insulation materials such as paper or foil are used for such insulation. These sheet insulation materials are primarily intended for two-dimensional insulation.In order to achieve continuous 360-degree insulation, individually used parts of the surface insulation materials must be bonded together.

[0012] The object of the invention is to provide a primary coil of a contactless energy transmission device or a contactless transformer for a rotor of an electrical machine, in particular a separately excited synchronous machine within a motor vehicle drive train, which has a compact design and high operational reliability even with high electrical power to be transmitted. In particular, this relates to the primary winding of a contactless transformer for a separately excited synchronous machine. Furthermore, the object of the invention is to provide a method for producing a corresponding primary coil.

[0013] This object is achieved by a primary coil of a contactless transformer for a separately excited synchronous machine, comprising a ferrite core which is designed in the shape of a hollow cylinder and has a groove-like recess on its radial outer side for receiving a winding. The primary coil further comprises a winding which is arranged in the groove-like recess and has a radially inner circumferential surface and a radially outer circumferential surface, a first axial side and a second axial side which is opposite the first axial side. The primary winding further comprises a tubular insulation which is arranged on the inner radial circumferential surface between the winding and the groove-like recess and encloses the winding on the first axial side and the second axial side.The tubular insulation forms a first section, which extends from the first axial side, at least in sections, in the axial direction over the winding on the radially outer surface. The tubular insulation further forms a second section, which extends from the second axial side, at least in sections, in the axial direction over the winding on the radially outer surface.

[0014] Advantageously, the tubular insulation, starting from the radially inner surface, encloses the winding on the first axial side toward the second axial side, or on the second axial side toward the first axial side, thus increasing the creepage distance. The creepage distance is the shortest distance along the surface of a solid insulating material between two conductive parts.

[0015] Particularly advantageous is the tubular insulation, which forms a continuous insulation between the winding and the ferrite core, reducing the risk of short circuits. As an alternative to a ferrite core, a core made of other hard or soft magnetic materials can be used.

[0016] First, the individual elements of the claimed subject matter of the invention are explained in the order of their relevance or their mention in the set of claims, and particularly preferred embodiments of the subject matter of the invention are described below.

[0017] A rotor is the rotating part of an electrical machine. The rotor includes, in particular, a rotor shaft. The rotor shaft can be hollow, which reduces weight and allows for the supply of lubricant or coolant to the rotor body.

[0018] The electric machine can be designed, in particular, as a rotary machine. The rotary machine can be configured, in particular, as a radial flux machine. A radial flux machine is characterized by the fact that the magnetic field lines in the air gap formed between the rotor and stator extend in a radial direction. The air gap is the gap between the rotor and stator. In a radial flux machine, this is a circular-ring-shaped gap in cross-section with a radial width corresponding to the distance between the rotor body and the stator body.

[0019] The electric machine is intended in particular for use within a drive train of a hybrid or fully electric motor vehicle. In particular, the electric machine is dimensioned such that vehicle speeds greater than 50 km / h, preferably greater than 80 km / h, and in particular greater than 100 km / h can be achieved. The electric motor particularly preferably has an output greater than 50 kW, preferably greater than 80 kW, and in particular greater than 150 kW. Furthermore, it is preferred that the electric machine provides speeds greater than 8,000 rpm, particularly preferably greater than 12,000 rpm, and most particularly preferably greater than 1,500 rpm. For the purposes of this application, motor vehicles are defined as land vehicles that are propelled by mechanical power without being tied to railway tracks.A motor vehicle can, for example, be selected from the group of passenger cars (PKW), trucks (HGVs), mopeds, light motor vehicles, motorcycles, buses (KOM) or tractors.

[0020] A contactless transformer, as used in separately excited synchronous machines, among other things, basically consists of a primary part and a secondary part, just like a transformer. This design allows alternating current to be transmitted using induction. Alternatively, the term inductive transformer can also be used. If, for example, a single-phase alternating current is applied to the primary part, a magnetic field is created in the winding of the primary coil, which also induces a single-phase alternating current in the winding of the secondary coil. The amount of the secondary voltage can be adjusted based on the number of turns in the primary and secondary parts, as well as the primary voltage. The amount of the primary voltage and the number of turns vary depending on the application. In some cases, the amount of the primary voltage is significantly higher than the amount of the secondary voltage, which in turn requires more complex insulation.

[0021] The inductive transformer can be arranged within a hollow shaft. The hollow shaft can be constructed in one piece or in multiple pieces. It is generally conceivable for the hollow shaft to be completely or partially penetrated by an opening extending longitudinally along the hollow shaft. For example, it would also be conceivable for the hollow shaft to have a blind hole into which the inductive transformer can then be inserted. The hollow shaft is preferably formed from a metallic material, particularly steel.

[0022] The inductive transformer is configured to transmit electrical powers preferably greater than 1 kW, and particularly preferably greater than 2 kW, at least for a short time, without electrically or thermally overloading the transformer. Most preferably, the inductive transformer is configured to transmit electrical powers between 0.5 kW and 10 kW, preferably between 1 kW and 5 kW, and particularly preferably between 2 kW and 4 kW.

[0023] The windings of the transformer are made of an electrically conductive but non-ferromagnetic material, such as copper or aluminum, and are electrically insulated from one another. The windings are preferably aligned tangentially around the hollow shaft, resulting in a cylindrical ring-like winding body with a diameter and a longitudinal extension in the axial direction. Most preferably, the windings are wound around and / or into a core made of a ferromagnetic material.

[0024] The windings can be formed from one or more electrical conductors with a circular cross-section. It is also conceivable for the electrical conductors forming the winding to have a cross-sectional shape other than circular, in particular rectangular. Particularly preferably, the windings can be formed from insulated copper foils, which can be wound around one another in a similar way to a toilet paper roll.

[0025] According to an advantageous further development of the invention, the winding of the primary coil can have a higher number of turns than the winding of the secondary coil. This allows for a voltage conversion from the comparatively high battery voltage to the lower rotor voltage during the transfer of electrical energy between the primary coil and the secondary coil.

[0026] In this context, it is further preferred that an electrical voltage of 40-1500 V, preferably 100-1000 V, most preferably 300-850 V, be applied to the primary coil. Furthermore, it is preferable in this context that a voltage of 70-500 V be applied to the secondary coil.

[0027] The primary core and / or the secondary core are / are made of a ferromagnetic material, preferably a ferrite material. The primary core and / or secondary core can be constructed in multiple parts. The respective core parts are preferably essentially rotationally symmetrical, but can contain elements and recesses for securing or passing through additional components.

[0028] Particularly preferably, the primary core and / or the secondary core each have a ring-like spatial shape. Most preferably, the primary core and / or the secondary core have a U-shaped cross-sectional contour with a circumferential groove. The grooves of the U-shaped cross-sectional contours of the primary core and secondary core are preferably directed toward one another. It is also particularly preferred for the primary winding to run in the groove of the primary core and / or the secondary winding to run in the groove of the secondary core.

[0029] The axial length of the cylindrical ring-shaped secondary coil is preferably greater than 50%, preferably greater than 70%, of the radial outer diameter, especially the diameter of the secondary coil. Such an "elongated" winding design has proven particularly advantageous for energy transmission of the inductive transformer. Simply put, flat and elongated designs of the cylindrical ring-shaped secondary windings have proven particularly favorable with regard to the energy transmission properties of the inductive transformer.

[0030] It is further highly preferred that the axial length of the cylindrical ring-like primary coil is between 80-120% of the axial length of the cylindrical ring-like secondary coil, which can also contribute to good energy transfer between the windings.

[0031] Furthermore, it is advantageous that the two axial lengths of the cylindrical ring-like coils completely overlap axially, whereby the energy transfer between the primary coil and the secondary coil can be further optimized.

[0032] Furthermore, it may be advantageous for the primary core and secondary core to each form surfaces bordering the air gap, across which the magnetic flux is conducted from one part to the other. It is advantageous if the surfaces of the primary core bordering the air gap completely overlap the surfaces of the secondary core bordering the air gap, and / or if the surfaces of the secondary core bordering the air gap completely overlap the surfaces of the primary core bordering the air gap, thereby further optimizing the energy transfer between the primary winding and the secondary winding.

[0033] Tubular insulation, as defined in this application, is a flexible, tubular object made of a three-dimensional, solid insulating material. An insulating material is characterized by the fact that it is made of a non-conductive material, which means it has extremely low and thus negligible electrical conductivity. Insulating materials are used, among other things, in electrical engineering to limit the flow of electrical current to live parts. The solid insulating material preferably contracts strongly under the influence of heat or exhibits flexible properties, so that expansion under the influence of heat is also preferentially possible.

[0034] Heat-shrink tubing is a thermoplastic tube that contracts radially when exposed to heat (e.g., from a hot air gun). Heat-shrink tubing is used for insulation, mechanical protection, or sealing. Heat-shrink tubing is typically made of the following materials: polyolefins, polyvinylidene fluoride (PVDF), Viton, polyvinyl chloride (PVC), and polytetrafluoroethylene (PTFE or Teflon).

[0035] Embodiments:

[0036] According to one embodiment, outgoing portions of the winding extend along the radially outer surface from the first axial side to the second axial side. Furthermore, the second section of the tubular insulation extends from the second axial side to the first axial side between the winding and the outgoing portions. In addition, the second section of the tubular insulation extends on the radially outer surface from the first axial side to the second axial side, at least in sections, over the outgoing portions and the winding. The advantage of this embodiment is that the tubular insulation, which, starting from the radially inner surface, radially encloses the winding on the first axial side in the direction of the second axial side and on the second axial side in the direction of the first axial side, does not have to be interrupted.No penetration for the outlets needs to be made in the insulation. The outlets therefore initially run under the first section of the tubular insulation on the first axial side. In the area of ​​the second section of the tubular insulation, the outlets then run over the tubular insulation. Thus, the design of the outlets in combination with the tubular insulation also does not negatively affect the creepage distance.

[0037] According to a further embodiment, the first section and the second section of the tubular insulation overlap at least in sections on the radially outer surface of the winding in the axial direction.

[0038] This is particularly advantageous because it provides insulation that completely covers the winding and thus maximizes the creepage distance.

[0039] According to a further embodiment, the tubular insulation consists of several tubular insulations that overlap in the axial direction in the region of the groove-like recess on the radially inner surface of the winding. This advantageously allows for a design that is easy to assemble, since the ferrite core is not positioned in the axial center of a single tubular insulation, but rather, each tubular insulation can be pulled onto the ferrite core from a different axial direction. This facilitates automated handling of the ferrite cores.

[0040] According to a particularly preferred embodiment, the tubular insulation is a shrink tube.

[0041] When using heat-shrink tubing, the shrinking process allows for better simulation of corners and edges on the component to be insulated. This allows the winding to be inserted into the groove of the ferrite core in such a way that the highest possible fill factor is achieved. Particularly advantageous is the elimination of additional bonding or the application of adhesive joints, as is required with surface insulation materials. This not only saves costs, but also avoids potential defects in the insulation, thus maximizing creepage distances and reducing the risk of short circuits.

[0042] According to a further embodiment, the winding is designed as a stranded wire, in particular copper strand.

[0043] A particularly advantageous feature of stranded wire or litz wire is high-frequency stranded wire, also known as HF stranded wire. HF stranded wire consists of a large number of fine wires, usually insulated from each other by lacquer, which are interwoven in such a way that, on average, each individual wire occupies every position in the overall cross-section of the strand equally often. High-frequency stranded wire compensates for eddy currents and thus improves efficiency. Another advantage of high-frequency stranded wire is its improved thermal conductivity, and high-frequency losses are also reduced.

[0044] According to one embodiment, the ferrite core has an axially extending recess on its radial outer side, which serves to axially guide the winding leads from the groove-like recess to an axial end face. The advantage of the axially extending recess is that the leads do not protrude radially beyond the ferrite core. This allows for a space-optimized design of the primary coil to a secondary coil, as the air gap between the two can be optimally adjusted.

[0045] According to a further aspect, a contactless transformer for a separately excited synchronous machine comprises a primary coil according to one of the previously described aspects or embodiments. Furthermore, the contactless transformer comprises a secondary coil arranged coaxially with the primary coil, forming a radial air gap. According to a further aspect, a separately excited synchronous machine comprises a contactless transformer or a primary coil according to one of the previously described aspects or embodiments.

[0046] According to a further aspect, a method for producing a primary coil of a contactless transformer for a separately excited synchronous machine, wherein the primary coil has a tubular insulation, comprises the following steps: a) providing a hollow-cylindrical ferrite core having a groove-like recess on its radial outer side for receiving a winding, b) providing a plurality of mounting bushings designed as thin-walled, hollow-cylindrical components whose inner diameter is selected such that it substantially corresponds to the outer diameter of the ferrite core and enables the mounting bushings to be axially pushed over the outer diameter of the ferrite core, c) providing a tubular insulation having an inner diameter such that the tubular insulation can be arranged over the mounting bushings and the ferrite core,wherein the tubular insulation has a greater axial extent than the ferrite core, d) arranging the mounting bushings on opposite axial sides of the ferrite core and aligning the tubular insulation such that the tubular insulation protrudes beyond the ferrite core in the axial direction, e) applying a winding in the region of the groove-like recess, wherein the winding outlets protrude in the radial direction on a first axial side of the groove-like recess, f) sliding the mounting bushing, which is arranged on a second axial side opposite the first axial side, in the axial direction such that the mounting bushing pushes the tubular insulation from the second axial side towards the first axial side over the winding, g) placing the winding outlets onto the pushed-on region of the tubular insulation, h) sliding the mounting bushing,which is arranged on the first axial side, in such an axial direction that the mounting bushing pushes the tubular insulation from the first axial side towards the second axial side over the winding and at least partially over the outgoing sections.

[0047] Particularly advantageous is the tubular insulation consisting of several tubular insulations that overlap axially in the area of ​​the groove-like recess on the radially inner surface of the winding. This allows for a design that is easy to assemble, as the ferrite core is not positioned in the axial center of a single tubular insulation, but rather, each tubular insulation can be pulled onto the ferrite core from a different axial direction. This facilitates automated handling of the ferrite cores.

[0048] According to an advantageous embodiment, the tubular insulation is a shrink tube and the method comprises the following further steps d1 ) shrinking the tubular insulation in the area of ​​the groove-like depression onto the ferrite core, f 1 ) shrinking the pushed-on tubular insulation in the area of ​​the groove-like depression (onto the winding), h1 ) shrinking the pushed-on tubular insulation in the area of ​​the groove-like depression (onto the winding and the outgoings), wherein step d1 ) takes place after step d), and step f1 ) takes place after step f), and step h1 ) takes place after step h).

[0049] When using heat shrink tubing, the shrinking process makes it possible to better simulate corners and edges on the component to be insulated. This allows the winding to be inserted into the groove of the ferrite core in such a way that the fill factor is as high as possible. Particularly preferably, additional bonding or the application of adhesive points as is required with surface insulating materials can be dispensed with, which on the one hand means cost savings and on the other hand avoids potential defects in the insulation, thus maximizing creepage distances and thus reducing the risk of short circuits. According to an advantageous embodiment, a negative pressure is applied in at least one of steps d1) or f1) or h1).

[0050] The beneficial effect of negative pressure during shrinking is that it prevents air pockets. In particular, it prevents air pockets between the insulation and the ferrite core, as well as between the insulation and the winding. Furthermore, the negative pressure results in a better adhesion of the tubular insulation or shrink sleeve to the ferrite core or winding, as well as to the terminals. This allows for better simulation of corners and edges on the component to be insulated, especially when using shrink sleeves.

[0051] According to an advantageous embodiment, in step h) the tubular insulation is pushed on in such a way that the tubular insulation is arranged at least in sections in two layers over the winding on the radially outer surface of the winding.

[0052] This is particularly advantageous because it provides insulation that completely covers the winding and thus maximizes the creepage distance.

[0053] The invention and the technical environment are explained in more detail below with reference to the figures. It should be noted that the invention is not intended to be limited by the exemplary embodiments shown. In particular, unless explicitly stated otherwise, it is also possible to extract partial aspects of the facts explained in the figures and combine them with other components and findings from the present description and / or figures. In particular, it should be noted that the figures and in particular the proportionalities shown are only schematic. The same reference symbols designate the same objects, so that explanations from other figures can be used as a supplement if necessary. Terms such as “radial”, “axial” or similar refer to the axis of rotation of the electrical machine, unless a different referencing is explicitly used.Furthermore, in order to improve the readability of the figures, only individual or a few identical elements of a reference symbol may be provided.

[0054] It shows:

[0055] Figure 1 A section through a primary coil of a contactless transformer for a separately excited synchronous machine

[0056] Figure 2 A section through the primary coil according to Figure 1 in a first

[0057] Assembly step.

[0058] Figure 3 A section through the primary coil according to Figure 1 in a second

[0059] Assembly step.

[0060] Figure 4 A section through the primary coil according to Figure 1 in a third

[0061] Assembly step.

[0062] Figure 5 A section through the primary coil according to Figure 1 in a fourth

[0063] Assembly step.

[0064] Figure 6 A section through the primary coil according to Figure 1 in a fifth

[0065] Assembly step.

[0066] Figure 7 A section through the primary coil according to Figure 1 in a sixth

[0067] Assembly step.

[0068] Figure 1 shows a section through a primary coil 1 of a contactless transformer for a separately excited synchronous machine.

[0069] The primary coil 1 comprises a ferrite core 2 and a winding 4. The winding 4 is encased on a radially inner surface and a radially outer surface, on a first axial side and on a second axial side opposite the first axial side, by a tubular insulation 5, which is designed as a shrink tube 9. The winding 4 is arranged in a groove-like recess 3 of the otherwise hollow-cylindrical ferrite core. The groove-like recess 3 is located on a radially outer side of the ferrite core 2. In cross-section, this results in a substantially U-shaped contour.

[0070] The hose-like insulation thus extends between the inner radial surface of the winding 4 between this and the groove-like recess 3, and extends further on the first and on the second axial side of the winding 4 and encloses these by forming a first and second section 6,7.

[0071] The second section 7 extends from the second axial side in the axial direction over the winding 4 on the radially outer surface.

[0072] The first section 6 of the tubular insulation extends from the first axial side in the axial direction, at least in sections, over the winding 4 on the radially outer surface. In the present embodiment, the first section 6 forms a two-layer insulation with the second section 7, since the second and first sections 6, 7 overlap in the axial direction on the radially outer surface of the winding 4.

[0073] The winding forms outgoing leads 8 on the first axial side, by means of which the winding can be connected to a current or voltage source. The outgoing leads 8 extend along the radially outer surface from the first axial side to the second axial side. They extend in the axial direction between the first section 6 of the tubular insulation 5 and the second section 7 of the tubular insulation 5. The outgoing leads 8 are led out of the groove-like depression 3 to an axial end face of the ferrite core by means of a recess 11 in the ferrite core, which recess runs in the axial direction on its radial outer side. The winding 4 is designed as a stranded wire 10, in particular as a copper strand or HF strand made of copper.

[0074] Figures 2 to 7 each show a section through the primary coil according to Figure 1 in different assembly steps.

[0075] A mounting bushing 12 is arranged on each of the opposite axial sides of the ferrite core 2. The mounting bushings 12 are preferably arranged before the tubular insulation 5 is placed over the ferrite core 2. For subsequent assembly steps, it is important that the mounting bushings 12 are designed with an inner diameter that essentially corresponds to the outer diameter of the ferrite core 2, yet allows the mounting bushings to be pushed on axially. In other words, the inner diameters of the mounting bushings 12 have a certain amount of play relative to the outer diameter of the ferrite core.

[0076] The tubular insulation is arranged centrally over the mounting bushings 12 and the ferrite core. The tubular insulation is selected such that the inner diameter of the tubular insulation essentially corresponds to the outer diameter of the mounting bushings, so that the tubular insulation 5 can be arranged over the mounting bushings 12 and the ferrite core 2, and an axial alignment of the tubular insulation is possible. The tubular insulation 5 protrudes in the axial direction over the ferrite core 2 on each of the axial sides of the ferrite core 2.

[0077] The hollow cylindrical ferrite core 2 has a groove-like recess 3 on its radial outer side for accommodating a winding 4. The mounting bushings 12 partially cover the ferrite core 2 in the axial direction, but not in the area of ​​the groove-like recess. The tubular insulation does not initially lie against the ferrite core 2 in the area of ​​the groove-like recess 3.

[0078] The tubular insulation has a greater axial extent than the ferrite core 2. For downstream assembly steps, it is important that the tubular insulation is designed in such a way that the tubular insulation 5 has an axial extent so that the tubular insulation is arranged at least in sections on the mounting bushing 12 until the mounting bushing 12 is pushed on. Figure 3 shows the assembly state after the tubular insulation 5 has been shrunk onto the ferrite core 2 in the area of ​​the groove-like recess 3. To avoid air pockets in the area of ​​the groove-like recess 3, a vacuum was applied. Due to the shrinking, the axial extent of the tubular insulation is reduced. The tubular insulation now lies against the ferrite core, even in the area of ​​the groove-like recess, and encloses the ferrite core in the circumferential direction.The hose-like insulation 5 is also arranged on the mounting bushings, at least in sections.

[0079] Figure 4 shows the assembly state after the application of a winding 8 in the region of the groove-like recess 3. The winding forms an essentially hollow cylindrical shape, having a radially inner surface and a radially outer surface, a first axial side and a second axial side which is opposite the first axial side. The tubular insulation 5 is arranged on the radially inner surface of the winding and thus between the winding and ferrite core. The outgoing leads 8 of the winding protrude in the radial direction on a first axial side of the groove-like recess 3, which corresponds to the first axial side of the winding 8. The tubular insulation 5 is arranged between the first axial side of the winding and the first axial side of the groove-like recess.

[0080] Figure 5 shows the assembly state during the sliding on of the mounting bushing 12, which is arranged on a second axial side of the ferrite core opposite the first axial side. The mounting bushing 12 slides the tubular insulation 5 on in the axial direction such that the tubular insulation 5 comes to lie over the winding 4 from the second axial side of the winding toward the first axial side. In other words, the tubular insulation is slipped over the winding, forming a second section 7, which is arranged at least in sections on the radially outer surface of the winding.

[0081] Figure 6 shows the assembly state after sliding on the mounting bushing 12 from Figure 5, shrinking the pushed-on tubular insulation 5 in the area of ​​the groove-like recess 3 onto the winding (4), and placing the outputs 8 of the winding 4 on the pushed-on area of ​​the tubular insulation 5. The mounting bushing 12, which was used for sliding on, has been removed and does not remain as part of the primary coil. Particularly preferably, the mounting bushing is reused.

[0082] Figure 7 shows the assembly state during the sliding on of the mounting bushing 12, which is arranged on the first axial side. The mounting bushing 12 pushes the tubular insulation 5 on in the axial direction such that the tubular insulation 5 comes to lie from the first axial side of the winding towards the second axial side over the winding 4 and at least partially over the outputs 8. In other words, the tubular insulation is slipped over the winding, forming a first section 6, which is arranged at least partially on the radially outer surface of the winding 4, the outputs 8, and the already shrunk-on second section 7.

[0083] In addition to what has already been described, Figure 1 shows the assembly state after sliding on the mounting bushing 12 from Figure 7, after shrinking the pushed-on tubular insulation 5 in the area of ​​the groove-like recess 3 onto the already shrunk-on tubular insulation, the winding 4, and the outputs 8. The mounting bushing 12, which was used for sliding on, has been removed and does not remain as part of the primary coil. Particularly preferably, the mounting bushing is reused.

[0084] List of reference symbols

Claims

Patent claims 1. Primary coil (1) of a contactless transformer for a separately excited synchronous machine, comprising - a ferrite core (2) which is hollow-cylindrical and has on its radial outer side a groove-like recess (3) for receiving a winding (4), - a winding (4) which is arranged in the groove-like recess (3), having a radially inner surface and a radially outer surface, a first axial side and a second axial side which is opposite the first axial side, - a tubular insulation (5) which is arranged on the inner radial surface between the winding (4) and the groove-like depression (3) and encloses the winding (4) on the first axial side and the second axial side, characterized in that the tubular insulation (5) forms a first section (6) which extends from the first axial side at least in sections in the axial direction over the winding (4) on the radially outer surface, and the tubular insulation (5) forms a second section (7) which extends from the second axial side at least in sections in the axial direction over the winding (4) on the radially outer surface.

2. Primary coil (1) according to claim 1, wherein Outlets (8) of the winding (4) extend along the radially outer surface from the first axial side to the second axial side, and the second section (7) of the tubular insulation (5) extends from the second axial side to the first axial side between the winding (4) and the outlets (8), and the first section (6) of the tubular insulation (5) extends on the radially outer surface from the first axial side to the second axial side at least in sections over the outlets (8) and the winding (4).

3. Primary coil (1) according to one of the preceding claims, wherein the first section (6) and the second section (7) of the tubular insulation (5) overlap at least in sections on the radially outer surface of the winding (4) in the axial direction.

4. Primary coil (1) according to one of the preceding claims, wherein the tubular insulation (5) consists of several tubular insulations (5) which overlap in the axial direction on the radially inner surface of the winding (4) in the region of the groove-like depression (3).

5. Primary coil (1) according to one of the preceding claims, wherein the tubular insulation (5) is a shrink tube (9).

6. Primary coil (1) according to one of the preceding claims, wherein the winding (4) is designed as a stranded wire (10), in particular a copper strand.

7. Primary coil (1) according to one of claims 2 to 5, wherein the ferrite core (2) has a recess (11) extending in the axial direction on its radial outer side, which serves for the axial passage of the outgoing leads (8) of the winding (4) from the groove-like recess (3) to an axial end face.

8. Contactless transformer for a separately excited synchronous machine comprising - a primary coil (1) according to one of claims 1 to 6, - a secondary coil which is arranged coaxially to the primary coil (1) to form a radial air gap.

9. Separately excited synchronous machine comprising - a contactless transmitter according to claim 7, or - a primary coil (1) according to one of claims 1 to 6.

10. A method for producing a primary coil (1) of a contactless transformer for a separately excited synchronous machine, wherein the primary coil (1) has a tubular insulation (5), comprising the following steps: a) providing a hollow-cylindrical ferrite core (2) having a groove-like recess (3) on its radial outer side for receiving a winding (4), b) providing a plurality of mounting bushings (12) designed as thin-walled, hollow-cylindrical components whose inner diameter is selected such that it substantially corresponds to the outer diameter of the ferrite core (2) and enables the mounting bushings (12) to be pushed axially over the outer diameter of the ferrite core, c) providing a tubular insulation (5) having an inner diameter such that the tubular insulation (5) can be arranged over the mounting bushings (12) and the ferrite core (2),wherein the tubular insulation (5) has a greater axial extent than the ferrite core (2), d) arranging the mounting bushings (12) on opposite axial sides of the ferrite core (2) and aligning the tubular insulation (5) over the mounting bushings (12) and the ferrite core (2) in such a way that the tubular insulation (5) projects in the axial direction on the axial sides of the ferrite core (2) over the ferrite core (2), e) applying a winding (4) in the region of the groove-like recess (3), wherein the winding leads (8) protrude in the radial direction on a first axial side of the groove-like recess (3), f) sliding the mounting bushing (12), which is arranged on a second axial side of the ferrite core opposite the first axial side, in the axial direction such that the mounting bushing (12) slides the tubular insulation (5) from the second axial side in the direction of the first axial side over the winding (4), g) placing the leads (8) of the winding (4) onto the pushed-on region of the tubular insulation (5), h) sliding the mounting bushing (12), which is arranged on the first axial side, in the axial direction such that the mounting bushing (12) slides the tubular insulation (5) from the first axial side in the direction of the second axial side over the winding (4) and at least in sections over the leads (8) postpones.

11. The method according to claim 10, wherein the tubular insulation (5) is a shrink tube (9) and the method comprises the following further steps, d1 ) shrinking the tubular insulation (5) in the region of the groove-like depression (3) onto the ferrite core (2), f1 ) shrinking the pushed-on tubular insulation (5) in the region of the groove-like depression (3) onto the winding (4), h1 ) shrinking the pushed-on tubular insulation (5) in the region of the groove-like depression (3) onto the winding (4) and the outgoing leads (8), wherein step d1 ) takes place after step d), and step f1 ) takes place after step f), and step h1 ) takes place after step h).

12. The method according to claim 11, wherein in at least one of steps d1) or f1) or h1) a suppressant is applied.

13. Method according to one of claims 10 to 12, wherein in step h) the tubular insulation (5) is pushed on in such a way that the tubular insulation (5) is arranged at least in sections in two layers over the winding (4) on the radially outer surface of the winding (4).

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