Electrical coil of a stator composed of stranded wire, and method for producing such an electrical coil

Abstract

Proposed is an electrical coil (1) that has a winding wire (10) that is wound to form a plurality of coil turns (11). The winding wire (10) has a strand (160) that comprises a multiplicity of thin, twisted individual wires (110), and the strand (160) is sheathed with a turn insulation (150). Additionally, a fixing band (21-24) is wound around the coil turns (11) in at least one portion (16), which fixing band, when the coil (1) has been compressed, locally encases and geometrically fixes the coil turns (11). The invention also relates to the associated method for producing the coil (1) for a single tooth (100) of a stator, wherein the coil is produced on a dummy winding body and is subsequently mounted onto the tooth (100).

Description

[0001] ELECTRICAL COIL OF A STATOR MADE OF STRING WIRE AND

[0002] MANUFACTURING METHOD OF SUCH AN ELECTRIC COIL

[0003] Description

[0004] The invention relates to an electrical coil according to the preamble of claim 1 and a method for producing an electrical coil.

[0005] There is a need to improve electric motors with regard to the target parameters of efficiency, power-to-weight ratio, reliability, and service life, although these target parameters sometimes conflict with each other. This need is particularly evident in applications in the aviation industry, where the future of aircraft electrification depends significantly on the power density of the motors and generators used. Increasing the continuous power density of electric motors is largely limited by the current with which the electric motor can be operated. This current is influenced, among other things, by the conductor density and the associated copper fill factor.

[0006] To create compact coils used in electric motors, the use of stranded wires, made from a multitude of thin, twisted round wires, is known. Coils for electrical machines using stranded wire technology are described, for example, in DE 44 14 527 C1 and WO 2004 / 059817 A1. In contrast to flat copper conductors, stranded conductors have a lower copper fill factor because they are constructed from individual wires. For round individual wires, the theoretical maximum copper content is 78%. In reality, this value is significantly lower because the distribution of the individual wires does not correspond to a dense packing, and the free volume increases due to the winding, the twisting of the individual wires, and the residual stresses of the stranded wire.

[0007] It is known to compress winding wires made of stranded wire into a multi-layer coil after winding to increase the copper fill factor. However, compressing the strands can have a negative impact on the insulation properties, as the individual wires and their insulation can be damaged by high mechanical loads, or the compression can make it difficult to impregnate the coil with a resin.

[0008] The present invention is based on the object of providing a coil made from a stranded winding wire that is characterized by a high copper fill factor. Furthermore, a method for producing such a coil is to be provided.

[0009] This object is achieved by a coil having the features of claim 1 and a method having the features of claim 12. Embodiments of the invention are specified in the dependent claims.

[0010] According to a first aspect, the invention provides a coil comprising a winding wire wound into a plurality of coil turns. The winding wire comprises a stranded wire comprising a plurality of thin, twisted individual wires. Furthermore, the stranded wire is covered with winding insulation.

[0011] It is provided that the coil windings are wrapped in at least one section with a fixing band that locally encloses and geometrically fixes the coil windings in a pressed state of the coil.

[0012] The inventive solution is based on the idea of ​​securing the electrical coil in its compressed state, thereby preventing the coil from fanning out again after the compression pressure is removed. By preventing this, the high copper fill factor that develops during the compression of the coil is maintained without the copper fill factor subsequently decreasing again when the compression pressure is removed. This permanently ensures a high copper fill factor for the coil based on a stranded winding wire.

[0013] To fix the electrical coil in its pressed state, the invention provides for the use of at least one fixing band that is locally wound around at least one section of the coil windings. The fixing band geometrically fixes the coil windings and, in particular, prevents the coil windings from fanning out. The use of the at least one fixing band ensures dimensional stability of the coil and defined dimensions.

[0014] It should be noted that the fixing band only surrounds the coil locally or in sections, and not completely. Otherwise, it would not be possible, or not sufficiently possible, to finally impregnate the coil with a resin. The solution according to the invention thus enables the coil to be dimensional stable while still allowing for impregnation.

[0015] One embodiment of the invention provides that the fixing tape consists of a cured composite material, wherein the fixing tape is flexible before curing, so that it can be wound around the coil windings. An example of this is a fixing tape that is non-adhesive at room temperature, melts at elevated temperatures with high viscosity, and then cures after a short time. Such tapes are also referred to as B-stage tape or B-stage epoxy. One example of this is the material "Voltafix 2102" from the Isovolta Group, which is constructed as an epoxy resin / glass fiber composite material. Other pre-impregnated fibers (prepregs) can also be considered as materials for the fixing tape.

[0016] The individual wires of the stranded wire can each be provided with insulation in a manner known per se, so that no current flows between the individual wires of the stranded wire. Furthermore, it can be provided that the individual wires of the stranded wire are each provided with a baked enamel coating. A baked enamel coating represents a meltable and curable coating of the individual wires. The baked enamel coating surrounds the individual wire insulation of the individual wires of the stranded wire. In embodiments of the invention, the baked enamel hardens together with the fixing band, as will be explained in connection with the manufacturing method according to the invention. One embodiment of the invention provides that the coil windings are locally fixed by a plurality of fixing bands that are spaced apart from one another, so that free areas without fixing bands are formed between the fixing bands.For example, it is provided that the coil windings in the area of ​​a straight leg of the coil are locally covered by a fixing band, whereby several fixing bands can also be provided for each leg of the coil.

[0017] The fixing tape is initially wrapped around the coil windings and then hardens. It surrounds all coil windings in a particular section of the coil. In some configurations, it rests directly on the coil windings.

[0018] The stranded wire is provided with a winding insulation, which forms the outer sheath of the winding wire. The winding insulation is made of a porous, yet compressible or compressed material that is electrically insulating. The winding insulation is porous in that it has the ability to absorb resin during the coil impregnation. This enables subsequent full impregnation of the stranded wire, including the individual wires and the winding insulation itself.

[0019] At the same time, the winding insulation material is compressible, meaning it can shrink under pressure. This is advantageous for increasing the copper fill factor within the winding wire when the coil or winding wire is pressed together. Even in the pressed state, when the winding insulation is maximally compressed, it retains electrically insulating properties, ensuring reliable insulation between the coil windings. The porosity of the winding insulation is also retained in the compressed state of the coil. The winding insulation is wound around the stranded wire, for example, as a tape-like material.

[0020] The winding insulation can consist of typical woven materials with sufficient temperature stability, for example, based on polymers such as aramid fibers, PBO fibers, polyester fibers, nylon fibers, PTFE, etc. Inorganic fibers such as glass, quartz, ceramic, or basalt fibers or natural fibers are also suitable. Such materials can be used in the form of continuous fibers as woven or non-crimp fabrics, or as short fibers in the form of nonwovens. The use of porous standard insulation materials, for example, made of m-aramid fibers, is also possible. The winding insulation is impregnated with a resin when the coil is applied to a winding former such as a stator core. The resin also surrounds the stranded wire, including the individual wires of the stranded wire, and the coil is thus thoroughly impregnated with the resin.

[0021] A further embodiment provides for the winding wire to be given a rectangular cross-section during compression, so that it has a rectangular cross-section in the coil. This enables the provision of a high copper fill factor with regard to the compactness of the coil windings.

[0022] In a further aspect, the present invention relates to an electric machine with a rotor and a stator, wherein the stator has coils according to claim 1, each of which is applied to a winding body of a single tooth of the stator. The electric motor is, for example, a permanent magnet synchronous motor. In a permanent magnet synchronous motor, the stator is equipped with coils, while surface-mounted permanent magnets are attached to the rotor.

[0023] In a further aspect of the invention, the present invention relates to a method for producing an electrical coil, comprising the steps of:

[0024] Winding a winding wire consisting of a strand comprising a plurality of thin twisted individual wires and provided with a winding insulation into a coil having a plurality of coil turns, wherein the winding wire is wound onto a dummy winding body,

[0025] Pressing the coil at least in the direction of the coil axis, whereby on the one hand the strands of the winding wire are compressed and on the other hand the individual coil turns are pressed together so that the coil assumes a compressed state,

[0026] Winding at least one curable fixing tape around the coil windings before or after pressing; and

[0027] Curing of the fixing tape, whereby the cured fixing tape fixes the coil in the compressed state.

[0028] The method according to the invention is based on the idea of ​​arranging a fixing band locally on the outside of the coil and pressing the coil, wherein the fixing band hardens in the pressed or compressed state of the coil and thereby fixes it in the pressed or compressed state. This provides a permanently high copper fill factor of the coil. Pressing the coil comprises, on the one hand, compressing the strands of the winding wire, whereby the winding insulation is also compressed to enable compaction of the strands. This is done in such a way that the function of the winding insulation is retained and it continues to have sufficient porosity to absorb an impregnation resin in a later step. Pressing the coil also comprises pressing the individual coil windings together so that no cavities exist between the individual windings.

[0029] The coil is compressed along the coil axis, for example, in a vertical direction if the coil is aligned vertically. This compression occurs, for example, by reducing the distance between parallel plates in the vertical direction, thereby pressing the coil turns together. Additionally, the coil can also be compressed perpendicular to the coil axis, for example, in a horizontal direction. This can also be achieved, for example, by shortening the distance between parallel plates, whereby the coil turns are pressed together in a horizontal direction, for example, against a winding body.

[0030] After the fixing tape has hardened, the coil can be removed from the dummy winding body and applied to a winding body of a single tooth. The winding body of the single tooth, for example, comprises a laminated core, and the coil is inserted into a slot of the laminated core. The coil is designed in the form of a tooth-wound coil winding (also known as a concentrated winding). A plurality of such tooth-wound coils or individual teeth can be assembled to form a ring-shaped stator of an electrical machine.

[0031] The wrapping of at least one curable fixing band around the coil windings can occur before or after pressing. If the fixing band is wrapped around the coil windings before pressing, pressing takes place in one step. If the fixing band is wrapped around the coil windings after pressing, pressing takes place in two steps. The second case will be considered first below.

[0032] The pressing of the coil in two steps provides that in a first pressing step the coil is pre-pressed in the direction of the coil axis, wherein the strands of the winding wire are compressed and the individual coil turns are pressed together, after the first step the pre-pressed coil is removed from the dummy winding body, then the at least one fixing band is wound in a flexible, not yet cured state around the coil removed from the dummy winding body, then the coil provided with the at least one fixing band is placed again in the dummy winding body, in a second pressing step the coil is again pressed in the direction of the coil axis, wherein the individual coil turns are pressed together and the coil assumes a final compressed state, the fixing band hardens or is caused to harden when the coil is in the final compressed state, and the compressed,The coil fixed with the cured fixing tape is removed from the dummy winding body.

[0033] The two-step pressing process is due to the fact that when the pre-pressed coil is removed from the dummy winding body in order to apply the at least one fixing band, the coil already begins to fan out again to a small degree. After applying the at least one fixing band, it is therefore necessary to compress or press the coil again, this time with the fixing band attached. Once the coil is in its final compressed state, the fixing band hardens or is caused to harden, for example, by increasing the temperature. The finally compressed coil is fixed by the hardened fixing band and achieves dimensional stability. It can then be removed from the dummy winding body.

[0034] Alternatively, pressing takes place in just one step.It is provided that after the winding wire has been wound and before pressing, the at least one fixing band is wound in a flexible, not yet cured state around the not yet compressed coil (in this case it can be provided that the wound winding wire is removed from the dummy winding body, provided with the fixing band and then placed back on the dummy winding body), then the coil is pressed with the at least one fixing band in the direction of the coil axis, whereby on the one hand the strands of the winding wire are compressed and on the other hand the individual coil turns are pressed together so that the coil assumes a compressed state, the fixing band only hardens or is caused to harden (for example by an increase in temperature and subsequent cooling) when the coil is in the compressed state, and the compressed coil, fixed with the hardened fixing band, is removed from the dummy winding body.

[0035] In this design, the fixing band is already attached to the coil windings prior to pressing. The pressing and compacting of the coil results in the fixing band being arranged relatively loosely on the coil windings. Nevertheless, the coil windings or the coil are secured in the compacted state because the fixing band hardens and can thus fulfill the function of securing the coil despite the possible formation of loops or similar.

[0036] A further embodiment of the method provides for the individual wires of the stranded wire to be coated with a bonding varnish, whereby the bonding varnish cures or is caused to cure together with the insulating tape. Curing occurs, for example, by increasing the temperature and subsequent cooling. The curing of the bonding varnish together with the insulating tape ensures that the coil winding, when compressed, achieves strength and dimensional stability, even inside the stranded wire.

[0037] Embodiments of the invention provide that the winding wire is pressed to a rectangular cross-section.

[0038] A further embodiment provides that after the coil is applied to the winding body of the tooth-wound coil, the coil is impregnated, whereby the winding insulation and the strands of the winding wire are impregnated with a resin. The resin is absorbed by the porous winding insulation and additionally fills the remaining gaps between the individual strands.

[0039] The invention is explained in more detail below with reference to the figures of the drawing using several exemplary embodiments. They show:

[0040] Figure 1 shows schematically the structure of a winding wire comprising a strand with a plurality of individual wires and a winding insulation;

[0041] Figure 2 shows a perspective view of an embodiment of an electrical coil having a plurality of coil windings, wherein the coil windings are each wrapped in four sections with a fixing band that encloses the coil windings and geometrically fixes them; Figure 3 shows the coil of Figure 2 in a rear view;

[0042] Figure 4 schematically shows a dummy winding body used in a method for producing a coil according to Figures 2 and 3, wherein a winding wire consisting of a strand is wound onto the dummy winding body to provide a coil with a plurality of coil turns;

[0043] Figure 5 is a perspective view of an example of a single tooth of a stator of a permanent magnet synchronous motor comprising a coil; and

[0044] Figure 6 is a flowchart of a method for producing an electrical coil according to Figures 2 and 3.

[0045] For a better understanding of the background of the present invention, a coil according to the prior art will first be described with reference to Figure 5.

[0046] Figure 5 shows a perspective view of an example of a coil in the form of a single-tooth coil 1 wound on a coil former, wherein the single-tooth coil 1 and the coil former form a single tooth 100. The coil former comprises a sheet metal front plate 101, a sheet metal rear plate 102, and a winding former (not visible in Figure 5) that extends between the sheet metal front plate 101 and the sheet metal rear plate 102 and around which a winding wire 10 is wound, forming the coil 1. The coil former forms a groove between the sheet metal front plate 101 and the sheet metal rear plate 102. An insulating paper 104 can be arranged between the winding former and the winding wire 10. The winding former typically has a cuboid-shaped main body consisting of a stack of rectangular, enamel-insulated electrical sheets.A winding head carrier made of plastic (not visible in Figure 5) is placed on each end of the cuboid-shaped sheet-metal winding body, which provides the required rounding for the winding wire 10.

[0047] As can be seen in Figure 5, the winding wire 10 forms a plurality of turns 11, each of which forms straight longitudinal sections or legs 12 as well as further sections 13 at their ends, which in the illustrated embodiment are rounded and each folded by 180° around a winding head carrier. In the rounded sections 13, the winding wire 10 is guided without kinks. In the example shown, the winding wire 10 is formed by a flat copper conductor that is wound onto the winding body. Two contact ends 14, 15 of the winding wire 10 protrude to one side. They serve to electrically contact the winding wire 10. Alternatively, the winding wire 10 can be formed by a stranded wire.

[0048] As shown in Figure 5, the sheet metal front plate 101 has a smaller width than the sheet metal rear plate 102. This allows a plurality of individual teeth 100 to be assembled into a ring-shaped stator of an electrical machine, for example, a permanent magnet synchronous motor, wherein the interconnected sheet metal rear plates 102 form an outer stator ring of such a stator.

[0049] Particularly in the case where the winding wire 10 is formed by a stranded wire, the aim is to increase the copper fill factor of the winding wire 10 and thus of the coil. According to the invention, the winding wire is not wound directly onto the winding former of the individual tooth 100, but rather is first wound onto a dummy winding former. The resulting coil is compressed and fixed and then placed as an air-core coil onto the individual tooth 100, with the geometry of the individual tooth 100 being adapted accordingly for this purpose and, for example, having removable elements. For example, it can be provided that the sheet metal front plate 101 is designed to be removable in order to be able to place the wound coil 1 onto the winding former of the individual tooth 100.

[0050] Figure 1 schematically shows the structure of a winding wire 10 used in the invention, which is wound into a plurality of coil turns forming a coil. The winding wire consists of a stranded wire 160 comprising a plurality of thin, twisted individual wires 110. The individual wires 110 have a circular cross-section. A cavity or free volume 140 exists between the individual wires 110. The stranded wire 160, consisting of the individual wires 110, is surrounded by winding insulation 150.

[0051] The winding insulation 150 consists of a porous, compressible material that is electrically insulating. The material is designed such that the electrical insulation property is retained even after compression of the material. The winding insulation 150 consists, for example, of a woven fabric, a scrim, or a nonwoven based on polymers or organic fibers. As shown in the enlarged illustration on the left of Figure 1, each individual wire 110 is provided with an insulation 120 that electrically insulates the individual wire 110. A coating of baked enamel 130 is applied to the insulation 120. The coating of baked enamel 130 is suitable and intended to melt at elevated temperatures and subsequently harden.

[0052] Figure 2 shows an electrical coil 1 according to the present invention in its finished state. The coil 1 comprises a plurality of coil turns 11 formed by a winding wire 10. Each coil turn 11 comprises two straight legs 12 and, at its ends, two further sections 13, which are rounded in the illustrated embodiment, but could alternatively be straight, for example. Voltage is applied to the coil 1 via the contact ends 14, 15 of the winding wire 10, which protrude on one side of the coil 1.

[0053] The coil 1 further comprises four fixing bands 21-24, each of which wraps around the coil windings 11 in a section 16. The fixing bands 21-24 are made of a hardened composite material. They were cured while the coil 1 was in a compressed state, so that they geometrically fix the compressed state of the coil and provide dimensional stability for the coil 1.

[0054] In the illustrated embodiment, two fixing straps 21-24 are provided in the area of ​​each straight leg 12. These straps are arranged at opposite ends of the legs 12 and wrap around and geometrically fix the coil windings 11 locally in the sections 16. This arrangement of the fixing straps is to be understood only as an example.

[0055] Figure 3 shows the coil 1 of Figure 2 in a front and rear view. A coil axis 4 is also shown.

[0056] The coil 1 of Figures 2 and 3 consists of a winding wire 10, which is constructed according to Figure 1 and accordingly comprises a strand 160 with individual wires 110 and a winding insulation 150. To provide a compacted coil 1, a manufacturing process is required in which, firstly, the strands 160 of the winding wire 10 are compacted. This takes place under pressure, whereby the winding insulation 150 is also compressed, so that the overall internal volume of the winding wire 10 is reduced during the pressing process and, accordingly, the copper fill factor of the winding wire 10 is increased. In the manufacturing process of the coil 1, it is further provided that the individual coil turns 11 are pressed together so that no hollow spaces exist between them. The winding wire 10 also receives its final shape during the pressing process, which, in the illustrated embodiment, is not necessarily rectangular.

[0057] The manufacturing process is explained below by way of example with reference to Figures 4 and 6.

[0058] According to step 61 of Figure 6, a winding wire consisting of a strand of a plurality of thin, twisted individual wires and winding insulation is wound into a coil with a plurality of coil turns. The winding wire is wound onto a dummy winding body. Such a dummy winding body is illustrated as an example in Figure 4. This shows a dummy winding body 30, which is cuboid-shaped and, in the illustrated embodiment, has a small depth. The dummy winding body 30 is located on a platform 31 and is delimited by side walls 32.

[0059] According to step 62, the coil consisting of the individual coil turns is pressed in the direction of the coil axis (see coil axis 4 in Figure 3). This is done by moving parallel pressing plates (not shown in Figure 4) toward each other. For example, an upper pressing plate is moved toward the platform 31, which thereby forms a lower pressing plate.

[0060] As explained, during the coil compression process, the strands of the winding wire are compressed, and the individual coil turns are pressed together. In addition to compression along the coil axis or vertically, compression in a horizontal direction can also be achieved using suitable compression plates.

[0061] According to step 63, at least one curable fixing tape (corresponding to fixing tapes 21-24 in Figures 2 and 3) is wound around all coil turns. At this point, the fixing tape is not yet cured but is flexible, allowing it to be easily wound around the coil turns. The fixing tape is, for example, a curable tape that is non-adhesive at room temperature, but melts at elevated temperatures with high viscosity and subsequently hardens. Such a curable tape is also referred to as a "B-stage tape."

[0062] The winding of the at least one curable fixing tape around the coil windings can be carried out before or after pressing, as will be explained below.

[0063] According to step 64, the fixing band is cured, whereby the cured fixing band secures the coil in the compressed state. The curing of the fixing band thus occurs at a time when the coil is in the compressed or pressed state. This makes it possible to maintain the pressed state of the coil thanks to the cured fixing band and prevent the coil windings from fanning out after the pressing pressure is released.

[0064] To cure the fixing tape, for example, the temperature is increased so that the fixing tape melts. Such a temperature increase also causes the bonding varnish 130 surrounding the individual wires 110 of the stranded wire 160 (Figure 1) to melt. Upon cooling, the fixing tape hardens, and so does the bonding varnish. The hardened bonding varnish ensures that the increased copper content of the stranded wire, achieved through the pressing process, is fixed. The stranded wire can no longer expand in volume.

[0065] After the fixing tape has cured, the coil is removed from the dummy winding former 30 and applied to a winding former of a single tooth 100 as shown in Figure 5. The prefabricated air coil is inserted into a groove of the winding former. Finally, the coil is impregnated with an impregnating resin, whereby the impregnating resin fills the porous winding insulation 150 and, through this, also the free volume 140 (Figure 1) of the stranded wire 160.

[0066] In one embodiment, the fixing band is wound around the coil turns after a first pressing process, with the pressing taking place in a total of two steps. First, the coil is pre-pressed onto the dummy winding body 30. The pressed coil is then removed from the dummy winding body 30 in order to apply the at least one fixing band. However, after the pressed coil has been removed from the dummy winding body 30 and before the at least one fixing band is applied, the coil already fans out to a certain extent, so that it loses some of its compression. Therefore, after the at least one fixing band has been applied, the coil is placed back onto the dummy winding body 30 and pressed again in a second pressing step. The coil then assumes a final compressed state. Only after this state has been reached does the fixing band harden or is caused to harden by increasing the temperature.As the fixing tape hardens, it secures the final compacted state of the coil. The compacted coil, secured with the hardened fixing tape, can then be removed from the dummy winding body.

[0067] Alternatively, the coil can be pressed in a single step. The fixing tape is wound around the coil windings prior to pressing. For this purpose, the coil can be removed from the dummy winding body after the winding process, the fixing tape is applied, and the coil is then fed back into the dummy winding body. The coil is then pressed with the at least one fixing tape so that the coil assumes a compacted or pressed state. In the pressed state, the fixing tape either hardens or is melted and subsequently hardened, for example, by applying heat. After the fixing tape has hardened, the coil can be removed from the dummy winding body with the hardened fixing tape.Because the coil height is reduced during the pressing process (the reduction can be as much as 50%), the fuser tape does not adhere tightly to the coil windings after pressing and before curing, and may wrinkle. However, this is corrected by the subsequent heating and curing of the fuser tape.

[0068] It is understood that the invention is not limited to the embodiments described above, and various modifications and improvements may be made without departing from the concepts described herein. It is further understood that any of the described features may be used separately or in combination with any other features, provided they are not mutually exclusive. The disclosure extends to and encompasses all combinations and subcombinations of one or more features described herein. Where ranges are defined, these include all values ​​within these ranges, as well as all subranges that fall within a range.

Claims

Patent claims 1 . Electrical coil (1) comprising: a winding wire (10) wound into a plurality of coil turns (11), - wherein the winding wire (10) has a strand (160) which comprises a plurality of thin, twisted individual wires (110), and the strand (160) is covered with a winding insulation (150), characterized in that the coil windings (11) are wound in at least one section (16) with a fixing band (21-24) which locally coats and geometrically fixes the coil windings (11) in a pressed state of the coil (1).

2. Reel according to claim 1, characterized in that the fixing band (21-24) consists of a cured composite material.

3. Coil according to claim 1 or 2, characterized in that the individual wires (110) of the stranded wire (160) are each provided with an insulation (120).

4. Coil according to one of the preceding claims, characterized in that the individual wires (110) of the stranded wire (160) are each coated with a baked enamel coating (130).

5. Coil according to one of the preceding claims, characterized in that the coil windings (11) are locally fixed by several fixing bands (21-24) which are spaced apart from one another.

6. Coil according to one of the preceding claims, characterized in that the coil windings (11) are locally sheathed by the fixing band (21-24) in the region of a leg (12) of the coil.

7. Coil according to one of the preceding claims, characterized in that the winding insulation (150) consists of a porous, compressed material which is electrically insulating.

8. Coil according to claim 7, characterized in that the winding insulation (150) is formed by a woven fabric, a scrim or a fleece.

9. Coil according to one of the preceding claims, characterized in that the winding insulation (150) and the stranded wire (160) are impregnated with a resin.

10. Coil according to one of the preceding claims, characterized in that the winding wire (10) has a rectangular cross-section.

11. An electrical machine having a rotor and a stator, wherein the stator has coils (1) according to claim 1, each of which is applied to a winding body of a single tooth (100) of the stator.

12. A method for producing an electrical coil (1) according to claim 1, comprising the steps: - winding (61) a winding wire (10) having a strand (160) comprising a plurality of thin twisted individual wires (110) and provided with a winding insulation (150) to form a coil (1) having a plurality of coil turns (11), wherein the winding wire (10) is wound onto a dummy winding body (30), - pressing (62) the coil (1) at least in the direction of the coil axis (4), whereby on the one hand the strands (160) of the winding wire (10) are compressed and on the other hand the individual coil turns (11) are pressed against one another, so that the coil (1) assumes a compressed state, - winding (63) at least one curable fixing band (21-24) around the coil windings (11) before or after pressing, and - Curing (64) of the fixing band (21-24), whereby the cured fixing band (21-24) fixes the coil (1) in the compressed state.

13. The method according to claim 12, characterized in that the coil (1) is removed from the dummy winding body (30) after the fixing band (21-24) has hardened and is applied to a winding body of a single tooth (100), wherein the winding body of the single tooth (100) comprises a laminated core and the coil (1) is inserted into a groove of the laminated core.

14. Method according to claim 12 or 13, characterized in that the pressing of the coil (1) in the direction of the coil axis (4) takes place in two steps, wherein in a first pressing step, the coil is pre-pressed in the direction of the coil axis (4), wherein the strands (160) of the winding wire (10) are compressed and the individual coil turns (11) are pressed together, after the first step, the pre-pressed coil is removed from the dummy winding body (30), then the at least one fixing band (21-24) is wound in a flexible, not yet cured state around the coil removed from the dummy winding body (30), then the coil provided with the at least one fixing band (21-24) is reinserted into the dummy winding body (30), in a second pressing step, the coil is again pressed in the direction of the coil axis (4), wherein the individual coil turns (11) are pressed together and the coil (1) assumes a final compressed state, the fixing band (21-24) hardens or is caused to harden when the coil (1) is in the final compressed state, and the compressed,the coil (1) fixed with the cured fixing tape (21-24) is removed from the dummy winding body (30).

15. Method according to claim 12 or 13, characterized in that the pressing of the coil (1) in the direction of the coil axis (4) takes place in one step, wherein after the winding of the winding wire (10) and before the pressing, the at least one fixing band (21-24) is wound in a flexible, not yet cured state around the not yet compressed coil, then the coil is pressed with the at least one fixing band (21-24) in the direction of the coil axis (4), wherein on the one hand the strands (160) of the winding wire (10) are compressed and on the other hand the individual coil turns (11) are pressed against one another, so that the coil assumes a compressed state, the fixing band (21-24) only hardens or is caused to harden when the coil is in the compressed state, and the compressed coil, fixed with the hardened fixing band (21-24), is removed from the dummy winding body (30) is removed.

16. Method according to one of claims 12 to 15, characterized in that the individual wires (110) of the stranded wire (160) are each coated with a baked enamel coating (130), wherein the baked enamel coating (130) hardens or is caused to harden together with the insulating tape (21-24).

17. Method according to one of claims 12 to 16, characterized in that the winding wire (10) is pressed to a rectangular cross-section.

18. Method according to one of claims 12 to 17, as far as dependent on claim 13, characterized in that after applying the coil (1) to the winding body of the individual tooth (100), the coil is impregnated, wherein the winding insulation (150) and the strand (160) of the winding wire (10) are impregnated with a resin.

19. Method according to one of claims 12 to 18, characterized in that Pressing the coil (1) is also pressed perpendicular to the coil axis (4).

20. Method according to one of claims 12 to 19, characterized in that the coil (1) has two straight legs (12) and each leg (12) is wound with two spaced-apart fixing bands (21-24).

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