Component of an electric machine and methods for its manufacture

Abstract

Component (2) for an electric machine (1), comprising: - a carrier body (3) made of a magnetically conductive, in particular ferromagnetic, material; - at least one conductor section (7) embedded in the carrier body (3); - at least one web area (8) formed on the conductor section (7) in the support body (3), which is formed between the conductor section (7) and a surface (UR; US) of the support body (3), wherein the at least one web area (8) is formed with a high relative magnetic resistance compared to the material of the rest of the support body (3), wherein the at least one conductor section (7) is provided with a coating (34) which has a boiling point which is lower than a melting point of the material forming the support body (3), wherein the web area (8) is formed by forming a zone of reduced magnetic permeability around the conductor section (7) when the conductor section (7) is melted.

Description

Technical field

[0001] The invention relates generally to a component of an electrical machine, in particular a rotor of an asynchronous machine. State of the art

[0002] For example, compared to a brush-commutated electric motor, an asynchronous machine offers a high torque density at lower manufacturing and material costs. Furthermore, asynchronous machines are robust and have a long service life.

[0003] In asynchronous motors, a rotating stator field generated by the stator induces voltages in the short-circuited windings of the rotor. The currents resulting from these induced voltages generate a magnetic field in an air gap between the rotor and stator, with the magnetic field opposing its cause, namely the rotating stator field. Thus, a force acts on the rotor within the stator field, causing it to rotate.

[0004] Today, asynchronous machines are primarily designed with squirrel-cage rotors, which have short-circuit windings made especially of conductive copper or aluminum material.

[0005] The short-circuit windings can be manufactured in a laminated rotor body by a casting process or inserted into the rotor body as plug-in windings.

[0006] The short-circuit windings can be located in longitudinal grooves of a cylindrical iron body composed of iron sheet discs. Furthermore, the axially extending sections of the short-circuit windings, which form a so-called cage armature, can be short-circuited to each other at the end faces of the rotor, for example by a conductive ring.

[0007] To improve the mechanical strength of the rotor, especially in the case of a high-speed rotor with a comparatively high moment of inertia, the short-circuit windings can be embedded in the rotor body. In this case, a web made of the magnetically conductive material of the rotor body is formed radially between the air gap and an axially extending section of the short-circuit winding.

[0008] Due to the machine's design, magnetic short circuits can occur between adjacent rotor poles via the bridge, forming between adjacent conductor faces of the short-circuited windings. However, the short-circuited portion of the resulting magnetic field does not contribute to torque generation and therefore reduces the machine's efficiency.

[0009] A squirrel-cage motor for operation with a frequency converter is known from publication WO 90 / 04 281 A1. A conductor section of the rotor is received in a groove of the rotor, which opens towards the rotor's air gap in the form of a slot. A magnetic bridge, strongly curved towards the rotor conductor, is provided for magnetic bridging of the slot.

[0010] The German patent application DE 10 2010 021 470 A1 discloses a squirrel cage rotor for an asynchronous machine and a method for manufacturing the squirrel cage rotor.

[0011] From publication DE 10 2011 083 917 A1, a method for manufacturing a machine component for an electric machine is known, wherein the machine component is formed with a magnetically conductive material in which one or more magnetically non-conductive separation zones are provided. The separation zone is formed by introducing austenite-forming material during a melting process of the magnetically conductive material of the machine component, so that an austenitic microstructure is formed in the magnetically conductive material of the machine component.

[0012] The object of the present invention is to provide a component of an electric machine, in particular a rotor, especially a component which has good mechanical strength and efficient torque generation, and a method for manufacturing it. Disclosure of the invention

[0013] This problem is solved by a component for an electric machine according to claim 1, as well as by an electric machine and by a method for manufacturing a component for an electric machine according to the dependent claims.

[0014] Further advantageous embodiments of the present invention are specified in the dependent claims.

[0015] According to a first aspect, a component for an electric machine is created, comprising: - a carrier body made of a magnetically conductive, in particular ferromagnetic, material; - at least one conductor section embedded in the carrier body; - at least one web area formed on the conductor section in the support body, which is formed between the conductor section and a surface of the support body, wherein at least one web area is designed with a high relative magnetic resistance compared to the material of the rest of the support body.

[0016] One idea of ​​the above device is to provide an increase in the performance of an electric machine by targeted and finely adjusted guidance of the magnetic flux and, in particular, to reduce the magnetic flux through the bridge area.

[0017] This can be achieved by selectively and locally reducing the magnetic permeability of magnetically conductive materials, such as electrical steel, particularly stacked electrical steel, a process known as magnetic separation. By creating magnetically non-conductive or poorly conductive, yet mechanically stable separation zones between the individual rotor segments, magnetic stray losses can be reduced. Consequently, the torque density of the electrical machine component can be increased.

[0018] Furthermore, this idea allows for flexibility in the design of gap widths and conductor cross-sections.

[0019] In other words, the relative magnetic resistance in the river bridges or walkways can be increased through targeted measures without the rotor losing mechanical strength.

[0020] Because the conductor section is embedded in the support body, it may be possible for the conductor section to remain mechanically held against a mechanical load, such as a centrifugal force.

[0021] According to one embodiment, the web area can be formed by locally applying an injection material and subsequently remelting it locally. The injection material can be defined in its composition such that, by jointly melting the flux-conducting material of the support body and the injection material in the remelted area, a region of non-ferromagnetic material can be created for the entire temperature range occurring during manufacturing, standstill, or operation. For example, an austenitic microstructure, which is non-ferromagnetic, can be achieved.

[0022] To achieve this, the feedstock material can have a high content of, for example, nickel, manganese, and / or copper. The effect can be enhanced by the additional content of, for example, carbon and / or chromium. Possible compositions of the remelted area could be as follows: Nickel: 0% to 35% Manganese: 0% to 25% Copper: 0% to 10% Aluminum: 0% to 10% Carbon: 0% to 1.0% Chrome: 0% to 25% Rest: typical iron and steel accompanying elements

[0023] In particular, the input material can be supplied as a strip, wire, rod, or powder, and the remelting can be carried out by laser beam, electron beam, plasma, or electric arc. The input material is thus supplied, for example, as a strip, wire, rod, or powder before or during the remelting process, whereby the energy input for remelting can be achieved, for example, by a method known from welding technology, such as a laser beam, electron beam, plasma, or electric arc.

[0024] Furthermore, the component can be designed in such a way that the insertion material is chosen so that the web area is at least partially porous due to the remelting process.

[0025] The bridge area, which is at least partially porous, can exhibit a high relative magnetic resistance compared to the rest of the support body.

[0026] For special solutions, the melting process can simultaneously create a mechanical bond between individual elements of the flux-conducting material of the carrier body. Remelting is particularly advantageous when a mechanical bond between individual sheets is required in addition to magnetic separation. Welding in the axial direction eliminates the need for otherwise commonly used techniques, such as punched stacking points. By pinning the sheets to the infill material before the welding process, alignment, stacking, and—through subsequent remelting—magnetic separation can be achieved simultaneously.

[0027] In particular, rotor laminations, together with a copper winding or an aluminum winding, can be provided to create a zone with greatly reduced magnetic permeability without the need for an insertion material.

[0028] To promote the mixing in the microstructure and the reproducibility of the high relative magnetic resistance compared to the rest of the substrate, process parameters such as feed rate, irradiation angle and number of laser beams used are optimized.

[0029] Furthermore, the component can be designed such that the conductor section is coated with a material that has a boiling point lower than the melting point of the substrate material. This configuration can reduce the magnetic permeability of magnetically conductive materials, such as electrical steel, as follows.

[0030] The boiling point of zinc, for example, is 907 °C. It is known that fusion welding of galvanized steel components results in significant spatter and splatter formation. Therefore, the conductor sections 7, which are made of copper or aluminum, for example, can be coated with zinc before being installed in the electrical machine component.

[0031] Melting the carrier material, for example the electrical steel sheet, together with the galvanized conductor section through any fusion welding process can lead to pronounced ejecta and pores in web area 8 due to the zinc coating. This results in the desired local reduction of magnetic permeability and thus a reduction of magnetic flux in web area 8.

[0032] This effect of strong formation of ejecta and pores can also be achieved through other types of coatings, heat treatments, for example nitriding of the conductor, or for example by using alternative conductors made of cast aluminum.

[0033] Furthermore, the component of the electric machine can be designed such that a notch is provided on the support body near conductor section 7. This utilizes an effect that the fusion welding of copper and ferrous materials or aluminum and ferrous materials can lead to the formation of pronouncedly brittle intermetallic phases.

[0034] This effect can be used to create an area with reduced magnetic flux as follows: By designing the electrical steel sheet with mechanical rigidity, preferably in the form of a notch, reproducible cracks can be created in the weld area. When such an area is remelted, for example by a laser beam, high residual stresses can occur in the web area. This results in reproducible crack formation. Consequently, the magnetic flux is locally separated, thus achieving the desired local reduction in magnetic permeability.

[0035] According to another aspect, an electric machine is created with the above component, wherein the component is specifically designed as a rotor of the electric machine.

[0036] According to yet another aspect, a method for manufacturing a component for an electrical machine is created with the following steps: providing a carrier body in which at least one conductor section is embedded; increasing a relative magnetic resistance of a web area arranged between the conductor section and a surface of the carrier body.

[0037] One idea behind this method is to increase the performance of an electric machine by selectively and finely tuning the magnetic flux.

[0038] It may be possible to increase the relative magnetic resistance by modifying the material of the bridge area so that it becomes at least partially porous.

[0039] According to one embodiment, the change in relative magnetic resistance can be achieved by locally applying an injectable material to the surface of the carrier body near the conductor section and subsequently locally remelting it.

[0040] In particular, it may be provided that the increase in relative magnetic resistance is carried out by the following steps: - Providing a coating with an incorporation material, in particular zinc, on the conductor section, wherein the incorporation material has a boiling point which is lower than a melting point of the material of the carrier body, and - subsequent local melting of the conductor section at a temperature above the boiling point of the insertion material and below the melting point of the carrier material, so that at least in the web area a zone of reduced magnetic permeability is formed.

[0041] According to one embodiment, the relative magnetic resistance can be increased by forming an indentation on the surface of the web area near the conductor section, and subsequently performing local fusion welding at the indentation. Brief description of the drawings

[0042] Preferred embodiments of the present invention are explained in more detail below with reference to the accompanying drawings. These show: Fig. 1 a cross-section through an electric machine perpendicular to an axis of rotation; Fig. 2 a cross-section of a detail from Fig. 1; Fig. 3 a, b an effect of introducing an insertion material to form the bridge area with a high relative magnetic resistance; Fig. 4a, Fig. 4b and Fig. 4c a description of a method for producing a porous web area; Fig. 5a, Fig. 5b and Fig. 5c a description of a method for producing a web area with a crack. Description of embodiments

[0043] Fig. Figure 1 shows a cross-section perpendicular to an axial direction through an electric machine 1. The electric machine 1 has a rotor 2 (component) with a circular cylindrical rotor support body 3, which can rotate about an axis W. The rotor support body 3 is circumferentially provided with adjacent, axially extending conductor sections 7, which are embedded in the rotor support body 3. The conductor sections 7 are part of short-circuit windings with a winding plane parallel to the axis W. The conductor sections 7 can be short-circuited at the end faces of the rotor 2 and, for example, form a squirrel-cage rotor. The conductor sections 7 can have a circular or radially elongated cross-section.

[0044] Between the conductor sections 7 of the short-circuit windings and a shell surface UR of the rotor carrier body 3 there is a web area 8.

[0045] The rotor carrier body 3 is rotatably arranged in a circular cylindrical stator 5. The stator 5 is provided with stator teeth 10 spaced uniformly apart in the circumferential direction, which are separated from each other by stator grooves 9. The stator teeth 10 are surrounded by stator coils (not shown).

[0046] The stator 5 has an inwardly facing surface US, which is separated from the surface UR of the rotor carrier body 3 by an air gap 11 of width d.

[0047] Fig. Figure 2 shows an enlarged section from Fig.1. It can be seen that the conductor sections 7 are shown embedded in the rotor support body 3 and thereby form a web area 8, which is formed between a conductor section on the rotor support body and the outer circumference of the rotor support body 3 or the air gap 11.

[0048] The Fig. 3a and Fig. Figure 3b illustrates the effect of an increased relative magnetic resistance in the web area 8 compared to the material of the rotor carrier body 3. For clarity, field lines of the magnetic flux density B are shown here. A flux φ results from the magnetic flux density B.

[0049] In Fig.Figure 3a shows a section of the rotor support body 3 of the electric machine 1. A conductor section 7 with a current flow direction I perpendicular to the plane of the drawing is embedded in the rotor support body 3. A web area 8 is located between a surface UR, which represents an outer circumference of the rotor support body 3, and the conductor section 7. A stator 25 is arranged opposite the rotor support body 3, the surface US of which faces the rotor support body 3 and corresponds to the inner circumference US of the stator 25, being positioned at a distance d of an air gap 11.

[0050] The web section 8 can preferably be formed integrally with the rest of the rotor support body 3, for example from stacked ferromagnetic sheets that are electrically insulated from one another to prevent eddy currents during operation of the electric machine. In this case, if a current flows through the conductor section 7, the magnetic field lines B pass partly through the web section 8 of the rotor support body 3 and partly through the air gap 11 via the stator 25. However, the field lines passing within the rotor support body 3 do not contribute to the torque generation at the rotor and are therefore undesirable.

[0051] Fig. Figure 3b shows that instead of the bridge area 8 of the Fig.3a a web area 12 is provided, which is formed from a material with a high relative magnetic resistance. As a result, the magnetic flux density B' in the web area 12 is now significantly reduced, and the fraction of the magnetic flux density B' that is used in the representation of the Fig. 3a, which still runs through the bridge area 8, now runs through the air gap 11 into the stator 25. One effect is that a larger proportion of the magnetic flux density B' can contribute to the torque generation of the electric machine.

[0052] The material of the web area 12 can be modified, for example, by introducing a filler material from the outside, such as a strip, wire, rod, or powder. The web area is melted before or during the introduction of the filler material. The energy input for melting can be achieved using a method known from welding technology, for example, with a laser beam, electron beam, plasma, or electric arc.

[0053] The Fig. 4a, Fig. 4b, Fig. Figure 4c illustrates an increase in the relative magnetic resistance in the bridge area 8.

[0054] Fig.Figure 4a shows a section of a rotor support body 3 of an electric machine. A conductor section 7 is embedded in this rotor support body 3. A web area 8 is arranged between the conductor section 7 and an outer surface UR of the rotor support body. The conductor section 7 can be coated with a coating 34. The coating can consist of a material that has a lower boiling point than the melting point of the material 3 forming the support body. For example, the coating 34 can be made of zinc, which has a boiling point of 907 °C.

[0055] Will the bridge area 8, as in Fig. As shown in Figure 4b, if, for example, the bridge area 8 and the underlying area of ​​the conductor section 7 are irradiated with a strong laser radiation L, then the bridge area 8 and the underlying area of ​​the conductor section 7 are heated so that, as shown in the enlarged section A of the Fig.As shown in 4c, a porous or porous bridge area 32 is formed, which has a significantly increased magnetic resistance.

[0056] During the fusion welding of galvanized steel components, spatter and deposits can form. If the conductor sections are made of copper or aluminum, for example, they can be zinc-coated before being installed in the component of the electrical machine, particularly the rotor of an asynchronous machine. Melting of the material of web section 8 together with the melting of the galvanized conductor through any locally selected melting process can lead to pronounced spatter and pores due to the zinc coating, extending from conductor section 7 into web section 8. This results in an increase in the relative magnetic resistance and consequently a reduction in the magnetic flux through web section 8.

[0057] In this way, the field-line-displacing effect can be compared to the Fig. 3a and Fig. 3b can be achieved.

[0058] The Fig. 5a, Fig. 5b, Fig. Figure 5c illustrates an alternative or additional way to increase the relative magnetic resistance of the bridge area 8.

[0059] Fig. Figure 5a shows a rotor support body 3 of an electric machine 1. A conductor section 7 is embedded in the rotor support body 3. A web area 8 is arranged between a surface UR of the rotor support body 3 and the conductor section 7. A notch 6 is provided in this web area 8.

[0060] Fig. 5b illustrated, enlarged and shown in the Fig.5c, the effect of a high-energy laser beam directed at this indentation. The laser beam causes local fusion welding in the area of ​​the web region 8 between the material of the conductor section 7 and the material of the rotor carrier body 3. In some embodiments, this can be fusion welding of a copper conductor section 7 with an iron material or fusion welding of an aluminum conductor section 7 with an iron material.

[0061] It is known that during such fusion welding of different metals together, very brittle intermetallic phases can be formed.

[0062] By fusion welding the two aforementioned materials, i.e., copper with an iron-based material or aluminum with an iron-based material, at the location of the indentation 6, reproducible cracks can be produced in the weld area. This separates the magnetic flux in the area of ​​the crack formations, resulting in a web area 42 with a locally increased relative magnetic resistance compared to the material of the rest of the rotor carrier body 3.

[0063] Furthermore, when using a coated conductor section, it may be possible to apply an additional bonding material from the outside. It may also be possible to provide an additional notch when using a coated conductor section and then melt this notch in place. Finally, a combination of all three variants may be used.

Claims

[1] Component (2) for an electric machine (1), comprising: - a carrier body (3) made of a magnetically conductive, in particular ferromagnetic, material; - at least one conductor section (7) embedded in the carrier body (3); - at least one web area (8) formed on the conductor section (7) in the support body (3), which is formed between the conductor section (7) and a surface (UR; US) of the support body (3), wherein the at least one web area (8) is formed with a high relative magnetic resistance compared to the material of the rest of the support body (3), wherein the at least one conductor section (7) is provided with a coating (34) which has a boiling point which is lower than a melting point of the material forming the support body (3), wherein the web area (8) is formed by forming a zone of reduced magnetic permeability around the conductor section (7) when the conductor section (7) is melted. [2] Component (2) according to claim 1, wherein the web area (8) is formed by locally applying an incorporation material and subsequently carrying out local remelting. [3] Component (2) according to claim 2, wherein the web area (8) is formed by supplying the input material as a strip, wire, rod material or powder and by carrying out the remelting by laser beam, electron beam, plasma or arc. [4] Component (2) according to claim 2 or 3, wherein the insertion material is selected, in particular as a copper material or aluminium material, such that the web area (8) formed in particular from an iron material is formed by remelting with an at least partially porous intermetallic phase. [5] Component (2) according to claim 2 or 3, wherein the insertion material is selected such that the web area (8) is at least partially formed with an austenitic structure by remelting. [6] Component (2) according to one of the preceding claims, wherein a notch (6) is provided on the surface of the web area (8). [7] Electric machine (1) with a component (2) according to one of the preceding claims, wherein the component is in particular designed as a rotor of the electric machine (1), which is in particular designed as an asynchronous machine. [8] Method for manufacturing a component (2) of an electrical machine (1), comprising the steps: - Providing a support body (3) in which at least one conductor section (7) is embedded; - Increasing the relative magnetic resistance of a web area (8) formed between the conductor section (7) and a surface (UR; US) of the support body (3), wherein the at least one conductor section (7) is provided with a coating (34) having a boiling point lower than the melting point of the material forming the support body (3), wherein the web area (8) is formed by creating a zone of reduced magnetic permeability around the conductor section (7) when the conductor section (7) is melted. [9] Method according to claim 8, wherein the increase in relative magnetic resistance is carried out by treating the material of the web area (8) such that it becomes at least partially porous or porous. [10] Method according to claim 8, wherein the increase of the relative magnetic resistance is carried out by treating the material of the web area (8) so that it becomes at least partially austenitic, in particular by melting with the addition of an austenite former as an incorporation material. [11] Method according to claims 8 to 10, wherein the increase in relative magnetic resistance is achieved by - local application of an injecting material to the surface (UR, US) on the carrier body (3) near the conductor section (7) and - subsequent local remelting is achieved. [12] Method according to one of claims 8 and 9, wherein increasing the relative magnetic resistance comprises the following steps: - Providing a coating (34) with an incorporation material, in particular zinc, on the conductor section (7) which is in particular made of copper or aluminium, wherein the incorporation material has a boiling point which is lower than a melting point of the material of the support body (3), and - subsequent local melting of the conductor section (7) at a temperature above the boiling point of the insertion material and below the melting point of the material of the support body (3), so that at least in the web area (8) a zone of reduced magnetic permeability is formed. [13] Method according to at least one of claims 8 to 10 above, wherein increasing the relative magnetic resistance comprises the following steps: - Forming an indentation (6) on the surface of the web area (8), and - subsequent local fusion welding at the notch (6).

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