WO2022243018A1

WO2022243018A1 - Coil assembly

Info

Publication number: WO2022243018A1
Application number: PCT/EP2022/061684
Authority: WO
Inventors: Thomas Gleixner; Peter GRÖPPEL; Marc Lessmann; Martin THUMMET; Markus Wild
Original assignee: Rolls-Royce Deutschland Ltd & Co Kg
Priority date: 2021-05-18
Filing date: 2022-05-02
Publication date: 2022-11-24
Also published as: DE102021112869A1

Abstract

The invention relates to a coil assembly (100) that comprises a wound core (4) and a coil (6), the coil (6) consisting of an isolated winding wire (5, 55) wound onto the wound core (4). The coil (6) has an outer face (60) suitable for contact with a cooling medium. According to the invention, the coil (6) has structures (521-524) on its outer face (60) that enlarge the surface of the outer face (60).

Description

coil arrangement

description

The invention relates to a coil arrangement according to the preamble of patent claim 1 .

There is a need to improve electric motors with regard to the target variables of efficiency, power-to-weight ratio, reliability and service life, with the target variables sometimes conflicting with one another. Such a need exists in particular for applications in the aviation industry, in which the future of aircraft electrification largely depends on the power density of the motors and generators to be used. The increase in the continuous power density (i.e. the power in continuous operation at constant load, so-called S1 operation) of electric motors is significantly limited by the current with which the electric motor can be operated. This is influenced on the one hand by the conductor density and the associated copper fill factor and on the other hand by the cooling, because the cooling determines the maximum possible losses.

The coils of high-performance electric motors are wound from insulated copper conductors. So-called direct conductor cooling is known for effective cooling of the conductors, in which the cooling liquid comes into direct contact with the current-carrying conductors. The direct conductor cooling represents a very efficient cooling method, since the thermal resistances are minimized.

There is a need to further improve the effectiveness of the cooling. Accordingly, the present invention is based on the object of providing a coil arrangement of an electromagnetic energy converter which enables cooling in an effective manner.

This object is achieved by a coil arrangement having the features of claim 1. Developments of the invention are specified in the dependent claims.

Accordingly, the present invention provides a coil assembly comprising a hub and a coil, the coil being comprised of insulated winding wire wound on the hub. In this case, the coil has an outside which is suitable for coming into contact with a cooling medium.

Provision is made for the coil to form structures on the outside which increase the surface area of the outside.

The invention is based on the idea of increasing the heat transport into a cooling medium of direct conductor cooling by providing an enlarged surface on the outside of the winding and thereby improving the cooling of the coil. The solution according to the invention is based on the finding that direct conductor cooling necessarily has at least two essential thermal resistances that must be overcome for heat dissipation, namely the thermal transition to the cooling medium and the winding insulation. One reason these resistances are relatively high is limited contact of the cooling medium with the winding wire. By increasing the surface area of the coil that comes into contact with a cooling medium, the solution according to the invention increases the contact of the cooling medium with the winding wire and thus enables increased heat transport. This reduces the thermal resistance due to the winding insulation and the heat transfer to the cooling medium. This means that an electrical machine in which the coil arrangement according to the invention is used can be operated either at a higher current (with better power density) or at a lower temperature (with greater safety).

One embodiment of the invention provides that the structures that increase the surface area are provided by the geometry of the winding wire, with the winding wire forming the structures. According to this embodiment variant, the structures are thus formed directly by the winding wire, which in its entirety forms the outside of the coil that comes into contact with a cooling medium. The surface-enlarging structures on the outside of the coil are thus provided by the sum of the surface-enlarging structures formed on the individual turns.

The surface-enlarging structures of the winding wire are formed on one end face of the winding wire, which forms the outside of the coil in the wound state. Any shape of this face that deviates from a straight or semi-circular shape is referred to as increasing the surface area. In particular, any form of this face is referred to as surface-enlarging, in which the total length of the outer contour of the face in the cross-sectional view is greater than the total length of a half circle.

In principle, a large number of shapes are possible for the realization of such surface-enlarging structures. Configurations in this regard provide that the winding wire, in the cross-sectional view, forms at least one projection or at least one groove-shaped indentation on its one end face, which forms the outside of the coil in the wound state. Other configurations provide that the winding wire forms a triangular shape at its one end in the cross-sectional view, with the winding wire tapering towards the apex of the triangle in the cross-sectional view. It can additionally be provided, for example, that the apex of the triangle is formed by a rounded area in order to further enlarge the surface.

One embodiment of the invention provides that the winding wire has the same winding wire geometry over its entire length. However, this is not necessarily the case. Alternatively, different sections of the winding wire, which are arranged in different areas on the outside of the coil in the wound state, can have a different winding wire geometry, so that the winding wire geometry on the outside is not homogeneous but varies.

The winding wire is, for example, a flat copper conductor provided with winding insulation.

A further embodiment of the invention provides that the winding wire, in the cross-sectional view, has a flattened contour on its other end, which in the wound state forms the inner side of the coil facing the winding core, which has a planar contact with the winding core or with one between the winding core and the coil arranged insulation paper has. In this case, it can be provided that the flattened structure is formed by a rectangular shape of the other end face in the cross-sectional view. Reduced by modifying the contour of the winding wire on the inside also the thermal contact resistance between the conductor and the winding body. This improves additional heat dissipation via the winding body.

In a further embodiment of the invention, the winding wire is not designed as a flat conductor, but is formed by a stranded wire with a multiplicity of individual wires each provided with winding insulation. The entirety of the individual wires forms the outside of the coil. In order to implement the surface-enlarging structures, this configuration provides for the surface-enlarging structures to be embossed into the outside of the coil. This is done, for example, by embossing the structures by pressing them into the strands or individual wires and then fixing the structures created in this way. Fixing can take place, for example, by means of encapsulation or paint.

Any structure that gives the outside of the coil a shape that deviates from a planar outside is considered to increase the surface area. A large number of shapes are possible here. An example of this provides that the outside of the coil is formed in a wavy manner in the cross-sectional view.

A further embodiment provides that the coil forms two main outer surfaces on its two coil sides, with the structures enlarging the surface being formed on at least one of the outer surfaces. A large number of variants are possible. According to a variant, the surface-increasing structures are formed only on one of the two main external surfaces. In a further variant, the surface-enlarging structures are embodied symmetrically on both main outer surfaces. In a further variant, the surface-enlarging structures are designed asymmetrically on both main outer surfaces and on these, with the asymmetry being able to show up in different shapes of the structures and/or their design in different areas. In a further variant, the surface-enlarging structures are provided alternatively or additionally in the area of the winding overhangs, in which the winding wire is folded over to form windings. These variants apply both to an embodiment of the structures on flat conductors and to an embodiment of the structures on stranded wires.

An embodiment of the invention provides that the coil is a single-tooth coil winding of a single-tooth coil. However, this is only to be understood as an example. The solution according to the invention is also possible with other types of windings, as long as these windings allow direct conductor cooling, in which the cooling liquid is guided past a defined side of the windings. In a further aspect of the invention, the present invention relates to an electrical machine with a rotor and a stator, the stator having coil arrangements according to claim 1 . The electrical machine is, for example, a permanent magnet synchronous motor (PMSM), in particular a PMSM with single-tooth coils in the stator.

The invention is explained in more detail below with reference to the figures of the drawing using several exemplary embodiments. Show it:

FIG. 1 shows a partially sectioned, perspective view of an exemplary embodiment of a coil arrangement with a winding core and a coil wound from a winding wire, the coil forming an outer surface whose surface is enlarged by structuring the winding wire;

FIG. 2 shows a schematic perspective view of a coil according to FIG. 1, with different winding wire geometries being implemented by way of example;

FIG. 3 shows the coil with the winding wire geometries of FIG. 2 in a cross-sectional view;

FIG. 4 shows an exemplary embodiment of a coil arrangement with a winding core and a coil wound from a winding wire made of stranded wire, the coil forming an outer side and structures enlarging the surface being embossed into the outer side of the coil;

FIG. 5 shows a perspective view of a single-tooth coil according to the prior art; and

FIG. 6 shows a single-tooth coil according to FIG. 5 in a perspective sectional view.

For a better understanding of the background of the present invention, a coil arrangement according to the prior art will first be described with reference to FIGS.

FIG. 5 shows a perspective view of an example of a coil arrangement 100 in the form of a single-tooth coil. The coil arrangement 100 comprises a bobbin 10 onto which a winding wire 5 is wound. The bobbin 10 comprises a sheet metal front plate 2, a sheet metal rear plate 3 and a winding core, which cannot be seen in FIG. 1, which extends between the sheet metal front plate 2 and the sheet metal rear plate 3 and around which the winding wire 5 is wound. Between the winding support and the winding wire 5 can an insulating paper 7 can be arranged. The winding core typically has a cuboid main body, which consists of a stack of rectangular, enamel-insulated electrical laminations. The wound winding wire 5 forms a coil 6.

In the exemplary embodiment shown, the winding wire 5 is formed by a flat copper conductor. It is wound onto the winding carrier and forms a large number of turns 50. The two ends 56, 57 of the winding wire 5 protrude upwards. Alternatively, the winding wire 5 can be formed by a strand.

As shown in FIG. 5, the front sheet metal panel 2 has a smaller width than the rear sheet metal panel 3, which is wider than the front sheet metal panel 2 in any case in a central region 31. This makes it possible to assemble a plurality of coil formers 10 or individual teeth to form a ring-shaped stator of an electrical machine, with the laminated rear plates 3 connected to one another forming an outer stator ring of such a stator.

It can be seen in FIG. 5 that the winding wire 5 forms windings 50 which each form straight sections and sections 58 which are rounded at their ends and in which they are wrapped around the winding core by 180°. The winding wire 5 is guided without kinks in the rounded sections 53 . In order to be able to wrap the winding wire 5 or the windings 50 in the rounded sections 53 around the angle bracket without kinking, a winding head carrier made of plastic (not visible in the illustration in Figure 5) is placed on the ends of the cuboid laminated winding core the required roundness for the winding wire 5 provides.

FIG. 6 schematically shows the coil arrangement 100 of FIG. 5 in a partially perspective view cut in the region of the winding core. The winding core 4 is shown in FIG. This is shown schematically as being in one piece with the sheet metal front panel 2 and the sheet metal rear panel 3 . Such a one-piece design can be given in a variant.

The coil 6 is formed by the wound winding wire 5, the winding wire 5 forming a multiplicity of turns 50 adjoining one another. The winding wire 5 forms an outer side 60 of the coil 6 in its entirety when wound. This outer side 60 is suitable for coming into contact with a cooling medium (not shown). The winding wire is in the form of a flat copper conductor and is provided with winding insulation (not shown). The winding wire 5 forms a first face 51 towards the winding core 4 and a second, outer face 52.

FIG. 1 shows a first exemplary embodiment of the present invention. The basic structure of the coil arrangement 100 corresponds to that of FIG. 6. The coil arrangement 100 thus comprises a winding core 4 onto which a coil 6 consisting of a winding wire 5 is wound. The winding wire 5 is designed as a flat conductor. The coil 6 forms an outer side 60 which is formed by the outer end faces 52 of the winding wire 5 .

An axial direction x, which corresponds to the longitudinal extent of the conductor 5, is also indicated in FIG. The thickness of the coil 6 corresponds to the radial direction r perpendicular thereto. In the case of direct conductor cooling, a cooling medium flows past the outside 60 of the coil 6 in the axial direction x. A silicone oil, for example, is used as the cooling medium.

The coil 6 forms structures 521 on its outside 60, which increase the surface area of the outside 60 and thus the heat transport into the cooling medium. In the exemplary embodiment shown, these structures are formed by projections 521 which the winding wire 5 forms on its second end face 52 . The surface-enlarging structures 521 are thus given by the geometry of the winding wire 5 in that its end face 52 is structured accordingly.

It is noted that the spool 62 forms flap outer surfaces 61 , 62 which are both part of the outside 60 of the spool 6 . Both Flaupt outer surfaces 61 , 62 are provided with a surface-enlarging structure 521 . Alternatively, it can be provided that only one of the Flaupt outer surfaces 61 , 62 is provided with a corresponding structure 521 . It is also pointed out that the bent areas of the winding wire 5, which are typically routed around the winding head carrier (not shown), can also be designed with corresponding surface-enlarging structures.

In further configurations, the winding wire 5 is not provided with the same winding wire geometry 521 over its entire length. As a result, it is possible for a corresponding surface-enlarging structuring of the outside 60 to be limited to specific axial areas and/or specific radial areas r.

The surface structuring of the winding wire 5 shown in FIG. 1 is only to be understood as an example. Further geometries of the winding wire 5 for surface structuring are shown by way of example on the basis of FIGS. There they are FIGS. 2 and 3 should be understood to mean that the surface structures described there correspond to FIG. 1 and are formed on the entire outside of the coil or parts thereof, without different structures being present at the same time. At the same time, however, it is pointed out that, as an alternative, it is fundamentally possible for a mixed surface structure to be produced, for example according to FIGS. 2 and 3, by forming different structures along different longitudinal sections of the winding wire 5 .

FIG. 2 shows the alternatives of a hemispherical shape 520 of end face 52, a rectangular projection 521 on end face 52, a groove-shaped indentation 522 on end face 52 and a triangular shape 523 of end face 52. The half-circle shape 520 represents the “normal” end face contour of the end face 52 of the winding wire 5. The winding wire geometries 521, 522, 523 deviating therefrom serve to increase the surface of such a normal end face contour. Numerous other variants are possible. For example, the protrusion 521 may have a protruding shape other than a rectangular cross-sectional shape. In another example, the outside 60 of the coil is corrugated.

In the cross-sectional view of FIG. 3 it can be seen that in the embodiment variant with a triangular shape 523 it can be provided that the apex of the triangle 523 forms a rounded area 5230 which further increases the surface area.

Further design variants provide that structures are deliberately introduced into the outside, which increase the turbulence of the cooling medium flowing past in order to improve the heat transfer coefficient.

It is further pointed out that, in the illustration in FIGS. Deviating from this, it is provided in the exemplary embodiment in FIG. Through this, the winding wire 5 nestles against the insulating paper 7 on the inside. In this way, thermal conduction to the likewise thermally conductive winding core 4 is increased.

A number of methods can be used to structure the winding wire 5 . A first method provides that the outer edge or face 52 of the winding wire 5 is flattened, for example by rolling or extrusion, for example to realize the structuring 523 of Figures 2 and 3. A second method provides that the additional Structures are provided by milling the corresponding end face 52. For example, grooves corresponding to structure 522 or cooling fins are milled into the outer surface of winding wire 5 . A third method provides for 3D printing of the coil, with all of the structures 521-523 shown being able to be generated. A fourth method provides for manufacturing the coil 6 from a block, for example by milling or water jet cutting, with corresponding structures such as the structures 521-523 shown being able to be produced.

FIG. 4 shows another initial example, which differs from the exemplary embodiments of FIGS. 1 to 3 in that the winding wire used is not a flat conductor, but a stranded wire that has a large number of individual wires 55 each provided with winding insulation. The individual wires 55 are shown schematically in FIG. When using a stranded wire, the separation between individual windings is lost in the case of the wound coil 6, at least in variant embodiments, with the entirety of the individual wires 55 forming the coil 6 and its outer side 60 as a whole. In this case, the outside 60 is designed to be approximately planar without further measures.

In order to form structures that increase the surface area of the outside 60, such structures are formed by pressing and then fixing the pressed-in molds. According to FIG. 4, a wavy structure 524 is pressed into the outer side 60, which increases the surface area of the outer side 60. The tool used for pressing has a negative form of the desired cooling structure. The pressed-in structure is fixed, for example, by means of a potting or a lacquer.

In the exemplary embodiment in FIG. 4, both main outer surfaces 61, 62 on the outside are provided with a structure 524, this being the case only by way of example. Especially when structuring the surface by pressing, it is possible in a simple manner to form different surface-enlarging structures in different axial or radial areas of the coil 6 . The structures can be embodied symmetrically or asymmetrically on the two main outer surfaces 61, 62 and/or in the area of the end winding supports.

The invention was described with reference to FIGS. 1-4 by way of example using a single-tooth coil. The invention can generally be used in all forms of electromagnetic energy converters, such as motors, generators, rotating or linear machines, transformers, induction furnaces, etc., which provide direct conductor cooling of a coil. It should be understood that the invention is not limited to the embodiments described above, and various modifications and improvements can be made without departing from the concepts described herein. It is further pointed out that any of the features described can 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 sub-combinations of one or more features described herein. If ranges are defined, these include all values within these ranges as well as all sub-ranges that fall within a range.

Claims

patent claims

1. Coil arrangement (100), which has: a winding core (4), a coil (6), which consists of a winding wire (5, 55) provided with insulation, which is wound on the winding core (4),

- wherein the coil (6) has an outer side (60) which is suitable for coming into contact with a cooling medium, characterized in that the coil (6) forms structures (521-524) on the outer side (60), which increase the surface area of the outside (60).

2. Coil arrangement according to claim 1, characterized in that the surface-enlarging structures (521-523) are provided by the geometry of the winding wire (5), the winding wire (5) forming the structures (521-523).

3. Coil arrangement according to claim 2, characterized in that the winding wire (5) in the cross-sectional view on its one end face (52), which forms the outer side (60) of the coil (6) in the wound state, has a straight or semi-circular shape different structure (521-523).

4. The coil arrangement as claimed in claim 2 or 3, characterized in that the winding wire (5), in the cross-sectional view, has at least one projection (521 ) trains.

5. Coil arrangement according to claim 2 or 3, characterized in that the winding wire (5) in the cross-sectional view on its one end face (52), which forms the outside (60) of the coil (6) in the wound state, at least one groove-shaped indentation ( 522) trains.

6. The coil arrangement as claimed in claim 2 or 3, characterized in that the winding wire (5) has a triangular shape (523) on its one end face (52), which forms the outside (60) of the coil (6) in the wound state, in the cross-sectional view. forms, wherein the winding wire (5) tapers in the cross-sectional view to the apex of the triangle.

7. Coil arrangement according to claim 6, characterized in that the apex of the triangle is formed by a rounded area (5230).

8. Coil arrangement according to one of claims 2 to 7, characterized in that the winding wire (5) has the same winding wire geometry over its entire length.

9. Coil arrangement according to one of the preceding claims, characterized in that the winding wire (5) is a flat copper conductor provided with insulation.

10. Coil arrangement according to one of the preceding claims, characterized in that the winding wire (5) in the cross-sectional view on its other end face (51), which in the wound state forms the inner side of the coil (6) facing the winding core (4), has a flattened Contour (512) which has a surface contact with the winding core (4) or with an insulating paper (7) arranged between the winding core (4) and the coil (6).

11. The coil arrangement as claimed in claim 10, characterized in that the flattened contour (512) is formed by a cross-sectional view of the other end face (51) being rectangular in shape.

12. Coil arrangement according to claim 1, characterized in that the winding wire (5) is formed by a stranded wire with a multiplicity of individual wires (55) each provided with winding insulation, the entirety of the individual wires (55) forming the outside (60) of the coil (6), and wherein the surface-enlarging structures (524) are embossed into the outside (60) of the coil (6).

13. Coil arrangement according to claim 12, characterized in that the structures (524) have been stamped onto the outside (60) by pressing.

14. Coil arrangement according to claim 12 or 13, characterized in that the surface-enlarging structures (524) give the outside (60) of the coil (6) a shape deviating from a planar outside (60).

15. Coil arrangement according to one of claims 12 to 14, characterized in that the outer side (60) of the coil (6) is formed wavy in the cross-sectional view.

16. Coil arrangement according to one of the preceding claims, characterized in that the coil (6) forms two main outer surfaces (61, 62) on its two coil sides, the structures (521-524) enlarging the surface being on at least one of the outer surfaces ( 61, 62) is formed.

17. Coil arrangement according to claim 16, characterized in that the structures (521-523) are formed on both main outer surfaces (61, 62) and symmetrically on these. 18. Coil arrangement according to claim 16, characterized in that the structures

(524) are formed on both main outer surfaces (61, 62) and asymmetrically on these.

19. Coil arrangement according to one of the preceding claims, characterized in that the coil (6) has a single-tooth coil winding

single tooth coil is.

20. Electrical machine with a rotor and a stator, wherein the stator has coil arrangements (100) according to claim 1.