ELECTRICAL MACHINE AND METHOD FOR FABRICATION OF A COIL OF AN ELECTRICAL MACHINE

Abstract

Provided is an electrical machine including a rotor and a stator with at least one coil, wherein the coil includes one or more windings of one or more tape-shaped conductors wherein the or each conductor has a longitudinal axis, wherein the coil includes two opposing straight sections and two opposing arc-shaped coil head sections, wherein the coil includes at least two torsion sections, in which the or each winding is twisted around the longitudinal axis of the or each conductor, so that a width direction of the one or each conductors in at least one of the straight sections is parallel or essentially parallel to a direction of a magnetic field generated or generatable by the rotor penetrating the at least one straight section.

Claims

1. An electrical machine comprising a rotor and a stator with at least one coil, wherein the coil comprises one or more windings of one or more tape-shaped conductors, wherein the or each conductor has a longitudinal axis, wherein the coil comprises two opposing straight sections and two opposing arc-shaped coil head sections, wherein the coil comprises at least two torsion sections, in which the or each winding is twisted around the longitudinal axis of the or each conductor, so that a width direction of the one or each conductors in at least one of the straight sections is parallel or essentially parallel to a direction of a magnetic field generated or generatable by the rotor penetrating the at least one straight section.

2. The electrical machine according to claim 1, wherein the coil comprises four torsion sections, which are each arranged between one of the coil head sections and one of the straight sections.

3. The electrical machine according to claim 1, wherein the width direction of the or each tape-shaped conductor in the coil head sections is parallel or essentially parallel to a bending axis of the respective coil head section.

4. The electrical machine according to claim 1, wherein a twist angle in each torsion section is ±90° or less.

5. The electrical machine according to claim 1, wherein the coil comprises a plurality of windings, wherein each winding abuts at least one neighbouring winding or wherein an insulating layer is disposed between two neighbouring windings.

6. The electrical machine according to claim 1, wherein the coil comprises a plurality of windings and at least one transposition section, in which a stacking order of the windings is changed.

7. The electrical machine according to claim 1, wherein the or each conductor is a superconductor, of either a high-temperature superconductor of the first generation or the second generation.

8. The electrical machine according to claim 7, wherein the or each conductor is a coated conductor comprising a coating layer and a superconducting layer, in particular a superconducting layer made of YBaCuO, or that the conductor comprises superconducting filaments, in particular filaments made of BiSrCaCuO, or that the conductor comprises a layer and/or at least one strand of MgB.sub.2 and/or NbTi and/or Nb.sub.3Sn.

9. The electrical machine no according to claim 1, wherein the rotor comprises at least one superconducting element, especially a superconducting element for the generation of the magnetic field.

10. The electrical machine according to claim 1, wherein the electrical machine is a synchronous machine or an induction machine.)

11. A method for fabrication of a coil of the electrical machine according to claim 1, comprising the steps: a) providing one or more tape-shaped conductors b) twisting of the one or each tape-shaped conductor, wherein a twist angle is determined in dependence of a calculated and/or a measured magnetic field of the rotor, c) forming of a plurality of windings from the one or each tape-shaped conductor, d) arranging of the windings, forming a coil, wherein the steps are conducted in the order a), b), c), d), or a), c), b) d), or a), c), d), b).

12. The method according to claim 11, wherein the windings are fixed to each other during arranging of the windings or that the windings are fixed to each other after arranging of the windings.

13. The method according to claim 11, wherein the twisting of the one or each tape-shaped conductor occurs by tilting a rotational axis of a spool, on which the one or each tape-shaped conductor is wound up, during unwinding of the one or each tape-shaped conductor.

14. The method according to claim 11, wherein the twisting of the one or each tape-shaped conductor and the forming of the plurality of windings is conducted by winding the one or more tape-shaped conductor around a coil carrier element.

Description

BRIEF DESCRIPTION

[0039] Some of the embodiments will be described in detail, with reference to the following figures, wherein like designations denote like members, wherein:

[0040] FIG. 1 shows a schematic sectional view on an electrical machine according to an embodiment of the invention;

[0041] FIG. 2 shows a schematic view on a first embodiment of a coil of an electrical machine according to the invention;

[0042] FIG. 3 shows a first sectional view of the first embodiment of the coil of an electrical machine according to the invention;

[0043] FIG. 4 a second sectional view of the first embodiment of the coil of the electrical machine according to the invention;

[0044] FIG. 5 a schematic top view of a second embodiment of a coil according to the invention;

[0045] FIG. 6 a schematic side view on a transposition section;

[0046] FIG. 7 shows schematic flow diagrams of a first embodiment of a method according to the invention;

[0047] FIG. 8 shows a second embodiment of a method for fabrication of a coil; and

[0048] FIG. 9 shows a third embodiment of a method for fabrication of a coil is shown.

DETAILED DESCRIPTION

[0049] In FIG. 1, a schematic sectional view of an electrical machine 1 according to embodiments of the invention is shown. The electrical machine 1 comprises a stator 2 and a rotor 3, wherein the rotor 3 is arranged inside the stator 2. The stator 2 comprises a stator core 4 exhibiting six poles 5, wherein around each pole a coil 6 is arranged. The stator 2 is separated from the rotor 3 by an air gap 7. The rotor 3 can generate a magnetic field expanding from the rotor 3 to the stator 2. The arrows 8 symbolize the magnitude and the direction of magnetic field lines of the magnetic field generated by the rotor 3. For reasons of clarity and comprehensibility, only the arrows 8 are shown, wherein the field lines of the magnetic field generated by the rotor 3 are omitted.

[0050] As it is indicated by the arrows 8, the magnetic field generated by the rotor 3 penetrates the coils 6. The course of the magnetic field lines or the directions of the arrows 8, respectively, is influenced by the material distribution and the shape of the stator 2, especially of the stator core 4 and/or the poles 5. In the vicinity of the coils 6 as well as inside the coils 6, the magnetic field generated by the rotor 3 is alternating during rotation of the rotor 3. During this rotation, the direction of the magnetic field in the vicinity of the coils 6 remains constant or almost constant, only the magnitude of the magnetic field varies between a value B.sub.max and the value B.sub.min, wherein B.sub.min can be in particular -B.sub.max. Therefore, the relation between the orientation of the coil 6 and the direction of the magnetic field remains also constant or almost constant during operation of the electrical machine 1.

[0051] The electrical machine 1 can be a synchronous machine. The rotor 3 of the electrical machine 1 can comprise at least one superconducting element, which is used for generation of the magnetic field. Also, the coil 6 of the stator 2 can be made of a superconducting material, as it will be described later. The electrical machine can comprise cooling means for cooling the stator 2 and/or the rotor 3 for maintaining the superconducting state of the superconducting coils 6 and/or the superconducting elements in the rotor 3, which are not shown in FIG. 1. As it is discernible from FIG. 1, each of the coils 6 comprises two straight sections 12 expanding in axial direction through the electrical machine 1, wherein a width direction of one or each conductor 10 forming the windings 9 of the coil 6 is aligned parallel to the direction of the magnetic field penetrating the respective straight sections 12 as indicated by the arrows 8.

[0052] In FIG. 2, a detailed view on a coil 6 is shown. In FIG. 2, only a half-coil is depicted, wherein the second half, which is not depicted, exhibits the same geometry as the shown half coil. The coil 6 comprises six windings 9 made from one or more tape-shaped conductors 10. It is possible, that one tape-shaped conductor 10 is wound around itself forming a plurality of windings 9. It is also possible that each winding is made from one tape-shaped conductor 10, wherein the plurality of conductors 10 or each winding, respectively, is electrically connected to each other forming the coil 6. It is also possible that each winding 9 is made from a plurality of stacked conductors 10 connected in parallel.

[0053] The or each conductor 10 comprises a tape-shaped geometry and has a width w and thickness t. The or each conductor 10 can be made of a superconducting material, for instance of a tape-shaped superconductor of the second generation comprising a superconducting layer made of YBaCuO. The superconducting part of the tape-shaped conductor may exhibit a thickness, which is about three orders of magnitudes smaller than its width. For instance, the width can be several millimetres, for instance between 4 mm and 40 mm. The thickness of the superconducting layer of the conductor 10 can be for instance between 1 and 2 μm. Besides the superconducting layer, the conductor 10 may comprise also a carrier layer like a metal substrate on which the superconducting layer is arranged and/or an insulation coating. Alternatively, it is possible that the conductor comprises superconducting filaments, in particular filaments made of BiSrCaCuO, or that the conductor comprises a layer and/or at least one strand of MgB.sub.2 and/or MbTi and/or Mb.sub.3Sm.

[0054] In the depicted coil 6, the windings 9 of the tape-shaped conductor 10 abut each other. Alternatively, it is possible, that between each winding 9, an insulating layer is arranged. The coil 6 can have more or less than six windings 9, it is in particular possible that it comprises between 20 and 200 windings.

[0055] The coil 6 has a race-track shape and comprises two coil head sections 11, wherein the second coil head section 11 on the other half of the coil is not depicted in FIG. 2. The coil 6 also comprises two straight sections 12 as well as four torsion sections 13, which are arranged each in between one of the straight sections 12 and one of the coil head sections 11. From the four torsion sections 13, two torsion sections 13 are shown between the depicted coil head section 11 and the portions of the two straight sections 12.

[0056] In the coil head sections 11, the conductors 10 are arranged in such manner, that the width direction of the conductors 10 is parallel to a bending axis 14 of the arc-shaped coil head sections 11. The width direction of the conductors 10 is orthogonal to a longitudinal axis of each of the conductors 10 and to a thickness direction of each of the conductors 10. In the torsion sections 13, the windings 9 are twisted around the longitudinal axis of the or each conductor, wherein the orientation of the width direction changes. The orientation of the width direction changes in the torsion sections from the alignment parallel to the axis of the coil head to an alignment parallel to the direction of the respective magnetic field B, as indicated by the arrows 8, which penetrates the respective straight sections.

[0057] It is discernible in FIG. 2, that in the straight sections 12, the width direction of the conductors of the windings in the respective straight sections 12 are aligned parallel or almost parallel to the direction of the magnetic field penetrating the respective straight section 12 as indicated by the arrows 8. By this parallel alignment of the width direction, the occurrence of losses, which are generated due to the varying amplitude of the magnetic field, are reduced since the area of the conductors, which is aligned orthogonal to the magnetic field, is determined by the thickness of the conductors 10 and not by their width.

[0058] The orientation of the conductors 10 towards the bending axis 14 in the coil head sections 11 can be seen in FIG. 3, which shows the sectional view through the cutting plane III-III'. It is discernible, that in the coil head sections 11, the width direction of the conductors 10 are parallel to the bending axis 14. Due to the twist of the windings in the torsion sections 13 in between the coil head sections 11 and the straight sections 12, the width direction of the conductors 10 is aligned parallel to the magnetic field B in the straight sections 12. This can be seen in FIG. 4, which shows the sectional view of the cutting plane IV-IV′ of FIG. 2. The alignment of the width direction of the conductors 10 is parallel to the direction of the magnetic field as symbolized by the arrows 8.

[0059] In FIG. 5, a second embodiment of a coil 6 according to embodiments of the invention is shown. The coil 6 comprises a race-track shape formed by the two arc-shaped coil head sections 11 and the two straight sections 12. In between the straight sections 12 and the coil head sections 11, four torsion sections 15, 16 are arranged, in which the windings 9 of the coil 6 are twisted around a longitudinal axis of the conductors 10. In this embodiment, the twisting angles of the torsion sections 15 is different from the twisting angle of the torsion section 16. In the torsion sections 15, the twisting angle is larger and the windings 9 of the straight section 12 in between the torsion sections 15 are twisted in a clockwise direction. Contrary, in the torsion section 16, the twisting angle is smaller and the windings 9 of the straight section 12 in between the torsion sections 16 are twisted in an anti-clockwise direction.

[0060] By using two different twisting angles in the torsion sections 15 and 16, an adaption of the orientation of the conductors 10 in each straight section 12 to the orientation of the magnetic field penetrating the respective straight section 12 is possible. In this embodiment, the windings 9 are formed by one single tape-shaped conductor 10, which is wound three times to form three windings 9. These three windings 9 are connected to each other in a connection section 17 located inside one of the coil head sections 11. It is also possible, that the connection section 17 is located inside one of the straight sections 12 or inside one of the torsion sections 15 or 16, respectively.

[0061] It is also possible, that the coil 6 comprises one or more transposition sections 18 as shown in FIG. 6. In the transposition section 18, a first winding 19 changes its position from a top position to a bottom position, so that the stacking order of the windings 9 of the coil 6 are changed. By cyclically changing the stacking order of in particular all of the windings, coupling currents between the windings 9 and losses related to the conduction of alternating current can be reduced. A coil 6 can have one or more transposition sections 18, which can be located each in one of the coil head sections 11, one of the straight sections 12 and/or one of the torsion sections 13, 15, 16. Additionally or alternatively, it is possible that one or more of the windings 9 of the coil 6 are formed from a plurality of stacked conductors 10, wherein at least a part of the stacked conductors 10 are transposed and/or wherein the stacked conductors 10 are forming a Roebel conductor.

[0062] In FIGS. 7 to 9, three embodiments of a method for fabrication of a coil of an electrical machine according to embodiments of the invention are shown. The methods each comprise the steps:

S1 Providing one or more tape-shaped conductors 10.
S2 Twisting of the one or each tape-shaped conductor 10, wherein a twist angle is determined in dependence of a calculated and/or a measured magnetic field of the rotor 3.
S3 Forming of a plurality of windings 9 from one or each tape-shaped conductor 10.
S4 Arranging of the windings 9 forming a coil 6.

[0063] In the first embodiment depicted in FIG. 1, first one or more tape-shaped conductors are provided in step S1. Afterwards in step S2, the one or each tape-shaped conductor 10 is twisted in at least two torsion sections of the conductor 10, wherein a twist angle is determined in dependence of a calculated and/or a measured magnetic field of the rotor 3. Since for a given electrical machine 1, the geometry of the rotor 3 and the stator 2, in particular of the stator coil 4, is known, the calculation of the magnetic field distribution in the area of the coil 6 is possible. Additionally or alternatively, a measurement of the magnetic field in the area of the coil 6 is possible. By the twisting of the one or each conductor 10, the orientation of a width direction of the one or each conductor 10 in the straight section 12 is adapted to the respective calculated and/or measured magnetic field, so that the width direction of the or each conductor 10 is aligned parallel or essentially parallel to the magnetic field penetrating the respective straight section 12.

[0064] Afterwards, in step S3, a plurality of windings 9 is formed from the one or each tape-shaped conductor 10 wherein each winding 9 comprises an arc-shaped section and a straight section. In step S4, the windings 9 are arranged forming a coil 6, wherein the arc-shaped sections of the windings 9 form an arc-shaped coil head section 11 of the coil 6 and wherein the straight sections of the windings 9 are forming the straight sections 12 of the coil 6. Accordingly, the torsion sections of the or each conductor are forming the torsion sections 13, 15, 16 of the coil.

[0065] A second embodiment of a method for fabrication of a coil is shown in FIG. 8. As a first step S1, one or more tape-shaped conductors 10 are provided. Subsequently, in step S3, from the one or each conductor 10, a plurality of windings 9 is formed, wherein each winding 9 comprises two arc-shaped sections and two straight sections. After forming of the windings, in step S2, each winding 9 is twisted in a torsion section around a twisting angle, wherein the twisting angle is determined in dependence of a calculated and/or measured magnetic field of the rotor 3. Afterwards, in step S4, the windings are arranged forming a coil 6 as previously described.

[0066] In FIG. 9, a third embodiment of a method for fabrication of a coil 6 is shown. After provision of one or more tape-shaped conductors 10 in step S1, a plurality of windings 9 is formed from the one or each tape-shaped conductor 10, wherein each winding 9 exhibits two opposing arc-shaped sections and two opposing straight sections. In subsequent step S4, the windings 9 are arranged forming a coil 6, so that the coil 6 exhibits two arc-shaped coil head sections 11 and two straight sections 12. Subsequently, in step S2, the windings 9 are twisted in at least two torsion sections 13, wherein the respective twisting angle is determined in dependence of a calculated and/or a measured magnetic field of the rotor 3.

[0067] For each of the three embodiments, a coil comprising two opposing arc-shaped coil head sections 11, two opposing straight sections 12 and at least two torsion sections 13, 15, 16 can be fabricated. In each of the three embodiments, the fixation of the windings 9 to each other may occur during arranging of the windings 9, for instance by applying an adhesive to the conductor 12 forming the windings 9. Alternatively, a fixing of the windings 9 can occur after arranging of the windings 9, hence when the coil 6 has been formed from the windings 9, wherein the fixing can occur for instance by immersing the coil 6 into a liquid adhesive.

[0068] In each of the three embodiments, the twisting of the one or each tape-shaped conductor 10 can occur by tilting a rotational axis of a spool, on which the one or each tape-shaped conductor 10 is wound up, wherein the tilting of the rotational axis occurs for instance during unwinding of the one or each tape-shaped conductor 10. By tilting the rotational axis of the spool carrying the tape-shaped conductor 10, the twisting of the one or each tape-shaped conductor 10 can occur directly during unwinding of the one or each tape-shaped conductor 10 forming the windings 9.

[0069] Alternatively, it is possible, that the twisting of the tape of the one or each tape-shaped conductor 12 as well as the forming of the windings 9 occurs by winding the one or each tape-shaped conductor 10 around a coil carrier element. By winding the one or each tape-shaped conductor 10 around the coil carrier element, both the arc-shaped coil head sections 11 and the straight sections 12 of the coil 6 can be formed as well as the twisting of the windings 9 in the respective torsion sections 13, 15, 16 can be obtained.

[0070] Although the present invention has been disclosed in the form of preferred embodiments and variations thereon, it will be understood that numerous additional modifications and variations could be made thereto without departing from the scope of the invention.

[0071] For the sake of clarity, it is to be understood that the use of “a” or “an” throughout this application does not exclude a plurality, and “comprising” does not exclude other steps or elements.