Wave winding conductor for an electric machine, and method for producing a wave winding

Abstract

The invention relates to a wave winding conductor for an electric machine and to a corresponding method for producing a wave winding for an electric machine. According to the invention, for this purpose, a wave winding conductor (10) for an electric machine is provided. Said wave winding conductor consists of a plurality of individual wires (100) which are insulated with respect to one another and arranged such that the wave winding conductor (10) has a substantially rectangular cross-sectional profile, the wave winding conductor (10) having a direction of lay (S) which is parallel to its conductor axis (L) and in which it is bent multiple times to form a wave winding, and the wave winding conductor (10) being surrounded on its peripheral surface by an electrically insulating strip-like bandage (200, 201, 202). The strip-like bandage (200, 201, 202) is applied, before the bending operation, to the peripheral surface over a specified conductor length such that the strip-like bandage (200, 201, 202) exhibits an overlap in the direction of the conductor axis (L) such that an integer number of layers is obtained.

Description

[0001] Wave winding conductor for electrical machine and method for producing a wave winding

[0002] The invention relates to a wave winding conductor for an electrical machine and a corresponding method for producing a wave winding for an electrical machine.

[0003] Electric machines are used to convert electrical energy into mechanical energy or vice versa. An electric machine designed as a prime mover for a motor vehicle is particularly suitable for use within the drivetrain of a hybrid or fully electric motor vehicle.

[0004] Wave winding conductors for electrical machines, which are inserted into corresponding slots in the stator as wave windings, are well known in many different designs. For example, there are wave windings with conductors made of solid individual wires with a round or any rectangular cross-section. A wave winding conductor can be designed as a long conductor strand that, bent several times according to the specified winding pattern, forms a wave winding in the electrical machine. However, the winding conductor can also consist of a plurality of different bent conductor sections, which then form the conductor strand of the wave winding via their respective welded ends.Such solid individual wires have a high fill factor and thus high power densities, but have the disadvantage that the conductor material - typically copper - is subjected to considerable stress at the various bending points required to form the wave winding, especially with very small bending radii. If small bending radii are to be achieved, as is the case, for example, with the production of wave windings using a winding blade, then so-called stranded conductors can be used. Although these have a lower fill factor than solid individual wires, they can withstand greater mechanical stress during the bending process because such a stranded conductor consists of a large number of individual wires, most of which are insulated from one another. Such stranded conductors are also available in various cross-sectional shapes, including round or differently profiled, such as rectangular, cross-sectional shapes.Wave winding conductors typically also have an insulating layer surrounding the conductor. This layer will be thicker the higher the excitation voltage and thus the current density generated by the wave winding. Such insulating layers are also known for various voltages, applications, and designs of wave windings in electrical machines. However, just like the waveguide material itself, these are also exposed to the specific mechanical stresses during the bending process of the wave winding.

[0005] The object of the invention is to provide a wave winding conductor and a corresponding method for producing such a wave winding conductor, which are particularly suitable for use in electrical machines with a small diameter and / or high excitation voltage of 800V.

[0006] According to the invention, this object is achieved by the wave winding conductor having the features of claim 1 and the method according to the method steps of claim 9.

[0007] Advantageous developments of the invention are defined in the respective dependent claims.

[0008] Because the band-shaped bandage is applied to the circumferential surface of an insulated wave winding conductor with a bandaged stranded conductor, which consists of a large number of mutually insulated individual wires, before bending over a predetermined conductor length - i.e., a previously defined area of ​​the wave winding conductor - in such a way that the band-shaped bandage overlaps in the direction of the conductor axis, resulting in an integer number of layers, tighter bending radii can be achieved while maintaining the insulation stability of the wave winding conductor, particularly in electrical machines with high excitation voltages. The overlap creates bandages that consist of several layers rolled out in the same direction and positioned one above the other, with a nearly constant insulation thickness, over the desired conductor length. The technically necessary layer thicknesses can be determined in the insulation design, for example, using Dakin's law.Due to their parallel connection, the insulation layer thickness of the individual wires should be as thin as possible to increase the fill factor within the stranded conductor. For conventional enameled wires, this is between 4 μm and 30 μm per individual wire. The insulation material can be a standard insulation varnish for winding wires based on polyamideimide.

[0009] The wave winding conductors according to the invention or wave windings produced using the method according to the invention are characterized by high insulation strength even after the bending and forming process step and can therefore be reliably used in electrical machines with excitation voltages of around 800 V. Bending radii that are typically 0.5 to 1.0 times the total diameter of the conductor can thus be undercut and realized without a significant reduction in insulation stability.

[0010] It is particularly advantageous if the band-shaped bandage consists of a first bandage and an overlying second bandage in the radial direction of the wave winding conductor, wherein an unwinding direction of the first bandage points in the lay direction of the wave winding conductor and a unwinding direction assigned to the second bandage is opposite to the unwinding direction of the first bandage. This ensures reliable insulation stability even with bending and wrapping geometries - in particular using a winding blade - in which the wave winding conductor is subject to torsional force. Thus, particularly with torsional wrapping geometries, it is important to ensure that the lay length of the bandage is smaller than the wrap width of a winding head, which is formed by multiple forming processes.

[0011] The bandages are expediently bonded together using so-called baked varnishes. This achieves greater media impermeability and, in addition, largely prevents the formation of pockets during forming. To ensure sufficient insulation for an application with an 800V excitation voltage, the invention preferably provides a finished bandage thickness of 80–200 μm. Ideally, the bandage is applied over the entire conductor length in such a way that the bandage has a virtually constant thickness. However, it is also conceivable that there are regions of varying thickness along the conductor length.For example, in individual areas that form the winding head of the wave winding created by the bending process, the bandage thickness could be greater than in areas that are later inserted into the slots, provided there is no tendon in the wave winding or, in multi-phase systems, there is only one phase per slot.

[0012] A preferred feature of the bandage is easier scalability in both its width and layer thickness, which allows a suitable total insulation layer thickness to be achieved not only through the number of layers but also through the bandage thickness.

[0013] To form multiple layers, they overlap by 50% to 80% in width, particularly in a range of approximately 50% to 75%. The greater the overlap, the more layers are formed within the bandage. This increases the creepage distances and thus the insulating effect of the bandage. Furthermore, the multi-layer construction increases the overall stiffness of the waveguide. An overlap of approximately 50% for two layers, approximately 67% for three layers, and approximately 75% for four layers has proven to be practical.

[0014] The bandage is preferably made of a polyimide film, since currently known insulation methods, such as extrusion using the PEEK process, cannot be implemented with stranded wires made of pre-insulated individual conductors.

[0015] It is particularly advantageous if, in an electrical machine with a stator and a rotor and a wave winding arranged in slots of the stator and / or rotor, the wave winding consists of the wave winding conductor designed according to the invention. This allows smaller electrical machines to be built for higher excitation voltages and thus more powerful motors. Furthermore, secondary insulation in the slots is essential, as the insulation effect is achieved directly in the bandage.

[0016] The method according to the invention for producing a wave winding with a wave winding conductor designed according to the invention comprises the following steps: providing a wave winding conductor consisting of a plurality of mutually insulated individual wires; applying a band-shaped bandage to a circumferential surface of the wave winding conductor, wherein the bandage is applied such that the band-shaped bandage overlaps in the direction of a conductor axis of the wave winding conductor such that an integer number of layers is achieved; and subsequently repeatedly forming the bandaged wave winding conductor such that a wave winding is ready for insertion into slots of a stator and / or rotor of the electrical machine.As a result, fewer process steps are necessary during production, since with the wave winding conductor provided according to the invention, no post-processing treatment of the wave winding in the slots themselves or even before the wave winding is introduced into the slots is necessary.

[0017] Preferably, the application of the band-shaped bandage first comprises applying a first bandage and then applying at least a second bandage, wherein an unwinding direction of the first bandage points in the lay direction of the wave winding conductor and an unwinding direction associated with the second bandage is opposite to the unwinding direction of the first bandage. This results in a particularly good bandage that still exhibits very reliable insulation properties even after bending, especially in tight bending radii.

[0018] Particularly advantageous properties of a wave winding according to the invention are achieved if, after the application of a first bandage - which could also be referred to as a partial bandage - this is then bonded by applying a baking varnish or similar substance, before a second partial bandage is applied in a further step, the unwinding direction of which is opposite to that of the first partial bandage, and a further baking varnish is then applied. These steps can also be supplemented with further partial bandages lying above it, each with an opposite unwinding direction. By means of such a large number of bonded partial bandages, each with an alternating unwinding direction, a highly reliable wave winding conductor can be achieved from a stranded conductor material with high insulation strength and, at the same time, flexibility for small bending radii.

[0019] With sufficient layer thickness, the bandage in the slot area of ​​the stator can be considered basic insulation, making it possible to dispense with separate slot insulation, e.g., using foils, insulating papers, laminates, or primary forming processes, in an electrical machine with wave winding conductors according to the invention. This optimizes the existing fill factor when adjusting the wire dimensions or enables the design of wider stator teeth with better magnetic properties. In particular, the good sliding properties of a bandage can be advantageous here, compensating for surface roughness on the laminated core and enabling damage-free assembly.

[0020] Furthermore, the method according to the invention can also include a step for profiling the wave winding conductor in order to create the desired shape and external dimensions of the conductor. This profiling can be performed before and / or after the taping process. This profiling step is then generally carried out using forming tools, which create the desired external contour by forming the individual wire cross-sections and a corresponding compression to create a smaller overall cross-section of the conductor with a lower air content.

[0021] With the method according to the invention, turnover widths of between 5 and 50 mm can be achieved in the winding head between the parallel wire sections formed by multiple forming processes. Furthermore, bending radii in the winding head geometries of less than 0.5 times the total conductor diameter can be realized. The turnover width for winding contours is the span between two wire positions between which the wire undergoes a 180° torsion and in which the wire sides outside the turnover area are mirrored.

[0022] The invention is preferably used in one of the previously described embodiments when the stranded conductor, i.e., the wave-winding conductor consisting of a plurality of mutually insulated individual wires, has a non-circular cross-sectional shape. Especially with such profiled conductor cross-sectional shapes, especially with nearly rectangular conductor cross-sections, the invention requires less deformation of the partial conductor cross-sections, which in turn reduces the wire and insulation stress. Furthermore, the necessary compression of the partial conductors consisting of smaller non-circular cross-sections is lower, which enables an increase in the electrical fill factor and thus a reduction in the DC resistance.

[0023] The invention is explained in more detail by way of example with reference to the drawings. They show schematically and not to scale:

[0024] Fig. 1 shows a first embodiment of a wave winding conductor according to the invention with a bandage

[0025] Fig. 2 shows a further embodiment of a wave winding conductor according to the invention with a first and second bandage

[0026] Fig. 3a, 3b, 3c Measurement results for the wave winding conductors manufactured according to the invention

[0027] Fig. 1 shows a section of a wave winding conductor 10 for use as a wave winding in an electrical machine. The wave winding conductor 10 itself consists of a plurality of mutually insulated individual wires 100, which are bundled in such a way as to create a profiled - here largely rectangular - conductor cross-section. Such a wave winding conductor 10 can also be referred to as a profiled stranded conductor. According to the invention, the wave winding conductor 10 is enclosed on its circumferential surface by a band-shaped bandage 200. This bandage 200 consists of an electrically insulating material, such as a polyimide film, and must have a finished thickness at the end of the bandaging process that is tailored to the respective performance parameters of the electrical machine. For excitation voltages of 800V, the finished thickness of the bandage 200 should be in the range of 80 - 200 μm.

[0028] The band-shaped bandage 200 was applied to the circumferential surface over a predetermined conductor length prior to a bending process of the wave winding conductor 10 in such a way that the band-shaped bandage 200 overlaps in the direction of the conductor axis L such that, perpendicular to the conductor axis, an integer number of layers is achieved on the outer surface of the stranded conductor 10. The bandage 200 is applied in such a way that it is unrolled in a lay direction S of the wave winding conductor 10. The lay direction S (which can also be referred to as the feed direction during forming) is the direction in which the wave winding conductor is drawn into a bending device and formed in a subsequent bending process. This means that a helical or helix-like bandage of a band-shaped insulation foil with a width B is created on the circumferential surface and is distributed over the conductor length of the wave winding conductor 10.By appropriately selecting the overlap between two adjacent sections of the strip-shaped insulation foil in a respective area of ​​the bandage overlap U, a bandage with multiple layers, in particular an integer number of layers, can be achieved. A bandage overlap U of approximately 50% of the width B of the bandage 200 is shown in Fig. 1. Such wave winding conductors with a "simple" bandage are particularly suitable for layered wave windings, especially those without a wrapover in the winding head of the wave winding of the electrical machine.

[0029] For winding contours based on pure bending geometries, such as those found in layered wave windings, a simple bandage with a single unwinding direction is sufficient, since the bending load in the turnaround area of ​​the winding head designed in this way generally only leads to stretching or compressing the bandage and not to any separation of the layers. This reduces the costs of semi-finished product production for layered wave windings.

[0030] In the embodiment shown in Fig. 2, the wave winding conductor has a band-shaped bandage 200, which consists of two partial bandages, namely a first bandage 201 and an overlying second bandage 202. The unwinding direction R1 of the first bandage 201 is selected such that it points in the lay direction S of the wave winding conductor 10, and the unwinding direction R2 of the second bandage 202 is selected such that it is opposite to the unwinding direction of the first bandage 201. In the embodiment shown in Fig. 2, a baking varnish was also applied in an intermediate step after the application of the first bandage 201 and after the application of the second bandage 202, in order to bond the bandages 201 and 202, and thus also the layers of insulation film created by the bandaging, which further increases the stability and insulation reliability of the bandage. Such wave winding conductors with double orMultiple bandages are also particularly suitable for wound wave windings, especially those with a wrap in the winding head of the wave winding of the electrical machine.

[0031] For winding contours that consist of a combination of bending and torsion geometries, such as those found in wave-wound or wrap-around windings, the use of such a double or multiple bandage with the features described above is advantageous because, in addition to stretching and compression, at least one partial bandage is locally subjected to torsion loads opposite to its unwinding direction. In single bandages, this could lead to buckling and pocket formation, thus deteriorating the clearance and creepage distances.

[0032] The invention allows the following advantages to be achieved in particular:

[0033] - Development of a suitable insulation layer for 800V applications of the electrical machine and retention of the insulation properties even after production of the wave winding;

[0034] - Realization of minimal bending and torsion radii;

[0035] - Mechanical stability of the insulation during the forming or production process;

[0036] - Sufficient resistance of the finished wave winding inserted into the slots, in particular to bending loads at the slot exit, as well as to torsional and bending loads during winding in the winding head;

[0037] - and also the maintenance of tightness during direct cooling.

[0038] Figures 3a-c show various test results obtained with the wave winding conductors manufactured according to the invention. The following corresponds to:

[0039] “Pix 1” = 1-fold bandage

[0040] “Pix 2” = 2-fold crossed bandage

[0041] Fig. 3a shows the results for the pure bending load. In conclusion, there is a slight reduction in the breakdown voltage (approximately 1.5 kV) under bending for "Pix 1" and no reduction in the breakdown voltage under torsion for "Pix 2" (a reduction equal to the standard deviation).

[0042] Fig. 3b shows the results for pure torsional loading. The conclusion is a significant reduction in the breakdown voltage (approximately 4 kV) under torsion for "Pix 1," while no reduction in the breakdown voltage under torsion for "Pix 2" (a reduction equal to the standard deviation).

[0043] Fig. 3c shows the results of the superimposed bending and torsion conditions. The conclusion is that this also shows a significant reduction in the breakdown voltage (approximately 4 to 6 kV) under torsion and bending for "Pix 1," as well as a slight reduction in the breakdown voltage (approximately 1 to 2 kV) under torsion and bending for "Pix 2."

[0044] List of reference symbols

[0045] 10 wave winding conductors

[0046] 100 single wires

[0047] L ladder axis

[0048] 200 bandages

[0049] 201 first bandage

[0050] 202 second bandage

[0051] B Width of the bandage

[0052] S Impact direction

[0053] R Rolling direction

[0054] R1 Unwind direction of the first drum

[0055] R2 Unwind direction of the second drum

[0056] U Bandage overlap

Claims

Patent claims 1. Wave winding conductor (10) for an electrical machine, consisting of a plurality of mutually insulated individual wires (100) which are arranged such that the wave winding conductor (10) has a largely rectangular cross-sectional profile, wherein the wave winding conductor (10) has a lay direction (S) parallel to its conductor axis (L) in which it is bent several times to form a wave winding, wherein the wave winding conductor (10) is enclosed on its circumferential surface by a band-shaped bandage (200, 201, 202) which has an electrically insulating effect, and wherein the band-shaped bandage (200, 201, 202) is applied to the circumferential surface over a predetermined conductor length before bending such that the band-shaped bandage (200, 201, 202) overlaps in the direction of the conductor axis (L) such that an integer number of layers is achieved.

2. Wave winding conductor according to claim 1, characterized in that the band-shaped bandage (200, 201, 202) consists of a first bandage (201) and an overlying second bandage (202) in the radial direction of the wave winding conductor, wherein a rolling direction (R1) of the first bandage (201) points in the lay direction (S) of the wave winding conductor (10) and a rolling direction (R2) assigned to the second bandage (202) is opposite to the rolling direction of the first bandage (201).

3. Wave winding conductor according to claim 2, characterized in that the bandages (200,201,202) are glued together by means of a baking varnish.

4. Wave winding conductor according to one of the preceding claims 1 to 3, characterized in that the bandage (200,201,202) has a finished thickness of 80 - 200 pm.

5. Wave winding conductor according to one of claims 1 - 4, characterized in that the band-shaped bandage (200,201,202) is a band with a width (B) and the band overlaps in its width (B) by 50% to 80% of the width (B).

6. Wave winding conductor according to one of the preceding claims, characterized in that the band of the bandage (200,201,202) consists of a polyimide film.

7. Electrical machine with a stator and a rotor and a wave winding arranged in slots of the stator and / or rotor, consisting of at least one wave winding conductor according to one of claims 1 to 6.

8. Electrical machine according to claim 7, characterized in that no further insulating means are provided in the slots of the stator.

9. A method for producing a wave winding for an electrical machine, wherein the wave winding consists of at least one wave winding conductor (10) according to one of claims 1 to 6 and the method comprises the following steps: - Providing a wave winding conductor (10) consisting of a plurality of mutually insulated individual wires (100); - applying a band-shaped bandage (200,201,202) to a circumferential surface of the wave winding conductor (10), wherein the bandage (200,201,202) is applied in such a way that the band-shaped bandage (200,201,202) overlaps in the direction of a conductor axis (L) of the wave winding conductor (10) in such a way that an integer number of layers is achieved; - subsequent multiple forming of the bandaged wave winding conductor so that a wave winding is ready for insertion into slots of a stator and / or rotor of the electrical machine.

10. Method according to claim 9, characterized in that the application of the band-shaped bandage first comprises the application of a first bandage (201) and then the application of at least one second bandage (202), wherein a rolling direction (R1) of the first bandage (201) points in the lay direction (S) of the wave winding conductor (10) and one of the second The unwinding direction (R2) assigned to the bandage (202) is opposite to the unwinding direction of the first bandage (201). 11 .Method according to claim 10, characterized in that after the application of the first bandage (201 ) and after the When applying the second or each further bandage (202), an intermediate step is carried out in which baking varnish is applied radially on the outside to bond the bandages.

12. Method according to one of claims 9 to 11, characterized in that winding head areas with a turning width between 5 mm and 30 mm are achieved by turning over.

13. Method according to claim 12, characterized in that bending radii of less than 0.5 times the total conductor diameter in the bending direction are achieved in the winding head regions.

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