Synchronous machine with starting resistor

Abstract

According to the invention, the synchronous machine (1) has a starting resistor, the starting resistor having an electrical conductor, the specific resistance of which differs from copper, and the starting resistor in particular having a hollow structure.

Description

Technical Field

[0001] The invention relates to a synchronous machine with a starting resistor. Background Art

[0002] When starting a synchronous machine, a starting resistor can be used as a component in the short-circuited rotor circuit, so that the starting torque is advantageously increased. The so-called "resistance wheel" used for this purpose has a given resistance and a given thermal capacity. During the starting phase and the high currents that occur, this absorbs the heat generated by the power loss at the resistor, so that the temperature increase at the resistor wheel moves below the limit value determined by the materials used (especially the insulating material).

[0003] It can be problematic, for example, that the resistance wheel is designed as a rotor assembly made of copper conductors with a very large total mass. This situation can have an adverse effect on the size and rotor dynamics of the machine. However, to achieve the required heat capacity, this may be necessary. The resistance wheel can be made of a large mass of copper conductors to obtain sufficient heat capacity. The copper conductors are arranged in the rotor assembly so that the required resistance is generated via the cross section and length of the conductors. For a conventional resistance wheel of a large synchronous machine, this can mean a typical mass of, for example, 400 kg. Summary of the invention

[0004] An object of the present invention is to design an improved synchronous machine.

[0005] A solution to this object is disclosed in claim 1. Further exemplary embodiments are disclosed in the dependent claims 2 to 9.

[0006] The synchronous machine has a starting resistor, wherein the starting resistor has an electrical conductor whose specific resistance differs from copper, wherein the starting resistor has in particular a hollow structure. The hollow structure can be opened or closed. A medium can be located in the hollow structure. A cooling channel or a closed volume can be implemented by means of the hollow structure or by means of a plurality of hollow structures.

[0007] In one embodiment of the synchronous machine, the specific resistance of the electrical conductor is greater than that of copper. Therefore, the resistance value can be increased by selecting a different material.

[0008] In one embodiment of the synchronous machine, the electrical conductor has a lower specific weight than copper. This has the advantage of lower inertia.

[0009] In one embodiment of the synchronous machine, the starting resistor has a phase change material. The phase change material can be located in one or more hollow structures. The phase change material can absorb thermal energy, in particular in a short period of time.

[0010] In one embodiment of the synchronous machine, the electrical conductor comprises aluminium or an aluminium alloy. Aluminium is a worse electrical conductor than copper, but aluminium is lighter than copper.

[0011] In one embodiment of the synchronous machine, the electrical conductor has a length which exceeds the size of the starting resistor by a multiple. Thus, the resistance can be further increased.

[0012] In one embodiment of the synchronous machine, the electrical conductor is designed as a hollow conductor.Inside the hollow conductor, the phase change material can be permanently encapsulated.

[0013] In one embodiment of the synchronous machine, the electrical conductors are manufactured using additive manufacturing. Thus, complex geometries can be manufactured simply.

[0014] In one embodiment of the synchronous machine, the starting resistor is surrounded by a pot-shaped element. A phase change material can be accommodated in the pot-shaped element, which forms a recombinant structure.

[0015] In principle, the starting resistor can also be made of a material that is less conductive than copper. Using a material with a correspondingly higher specific resistance than copper results in lower mass requirements for the material. However, in practice, the total heat to be dissipated is usually very high, so that the heat capacity of the reduced mass is not sufficient to keep the maximum temperature occurring at the resistor wheel below a given limit, so a hollow structure is required. For example, in synchronous machines, a first material with a higher specific resistance than copper is combined with a second material embedded in the material (the so-called phase change material) which results in lower mass requirements. Phase change materials (such as paraffin) have a relatively high heat capacity on the one hand, and secondly, absorb thermal energy during the phase change without further temperature increase. In principle, both the phase change from solid to liquid and the phase change from liquid to gas are suitable. The phase change material used can have a corresponding phase change temperature which is above the maximum ambient temperature and below the permissible temperature limit. Suitable materials have a high specific impedance, for example aluminium alloys, which are also suitable with regard to the heat capacity of the aluminium alloy and, as a lightweight material, also contribute to the dynamic properties of the rotor.

[0016] In one embodiment of the synchronous machine, a special design of the resistance wheel can be produced which can allow the arrangement of lightweight materials as very long conductors, so that the longest possible path is produced for the current.

[0017] In one embodiment of the synchronous machine, the conductor is designed as a hollow conductor, inside which the phase change material is permanently encapsulated. At the same time, in order to design the resistor wheel as compactly as possible, a design is selected in which, in particular, the hollow conductor occupies as much space as possible within the envelope structure of the entire resistor wheel. For example, the envelope structure can be a pot-shaped element.

[0018] The arrangement of the hollow conductor filled with phase change material has advantages, in particular, compared to an equally conceivable arrangement of the conductor in a container filled with phase change material, a large surface is achieved, which can advantageously be used for effective recooling, since the phase change that occurs must be reversed as quickly as possible in order to make further startup of the machine possible.

[0019] In one embodiment of the synchronous machine, this results in a cylindrical envelope of the rotor component, for example the entire resistance wheel, wherein the individual hollow conductors are arranged in a meander, spiral or other manner that saves as much space as possible.

[0020] As can be seen from this description, the above-mentioned design places high demands on the manufacturing process used. Firstly, the very long hollow conductor is made of a material that is sufficiently strong, lightweight and highly precise so that the rotational forces can be absorbed and the dynamics of the rotor are positively influenced as a whole. Secondly, the above-mentioned design includes a level of complexity that is difficult to implement in terms of manufacturing technology. One possibility for this case is the so-called additive manufacturing process (in particular, laser beam melting) in which the component is manufactured layer by layer in a powder bed by means of a laser beam. While being flexible at the same time, this case is feasible for using high geometric complexity (just as the geometric complexity provides the described hollow structure) compared to manufacturing methods with high equipment costs. In particular, specific high-strength aluminum alloys can be used for laser beam melting, in particular, the aluminum alloys meet the above-mentioned mechanical requirements well. Additive manufacturing processes are also subject to certain manufacturing restrictions. Therefore, during laser beam melting, since the heat energy introduced by the laser must be physically removed, typically, the structure cannot be built in a horizontal manner in the powder bed. In this respect, the arrangement of the hollow conductor is mainly advantageous in the axial direction. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] The features of the individual claims or the described subject matter can be easily combined with one another. In the following, the invention is presented and described in more detail using the drawings as examples. A person skilled in the art can combine the features shown in the drawings to form new embodiments without departing from the invention. The drawings show:

[0022] Figure 1 shows a spiral arrangement of hollow conductors,

[0023] Figure 2 shows a curved arrangement of hollow conductors,

[0024] Figure 3 A hollow conductor having a circular sector-shaped cross section is shown,

[0025] Figure 4 A can-shaped element is shown as a reorganization structure,

[0026] Figure 5 A hollow conductor with minimal support to the build platform is shown,

[0027] Figure 6 shows the electrical contact of the hollow conductor,

[0028] Figure 7 shows the arrangement of hollow conductors for improved powder removal,

[0029] Figure 8 A fan element for cooling is shown, and

[0030] Fig. 9 shows the reinforcement of the hollow conductors by the mesh structure, and DETAILED DESCRIPTION

[0031] exist Figure 1 The illustration in shows the spiral arrangement of the hollow conductor 10 from two perspectives (axial and radial). Axially, a series of multiple curved disks are obtained relative to the axis 11. This situation leads to a cylindrical envelope structure of the entire resistor wheel, in which the individual hollow conductors are arranged in a curved, spiral or other manner that saves as much space as possible.

[0032] exist Figure 2 The representation of FIG. 1 shows a helical arrangement of the hollow conductor 10 . Thus, the bend is wound around the axis 11 .

[0033] exist Figure 3 The representation of shows a hollow conductor 10 with a circular sector cross section. Thus, a space-saving design is obtained, for example, that is, instead of a circular cross section, a circular sector-shaped cross section is selected for the hollow conductor, so that the gaps between adjacent passages of the hollow conductor are minimal. At the same time, the hollow conductor can be arranged so that the resulting rotor assembly has the lowest possible imbalance.

[0034] exist Figure 4 The representation of FIG. 1 shows a starting resistor with a pot-shaped element 12, which is attached to a shaft 13. The start and end of the hollow conductor 10 are located at one of the two end faces of the cylindrical envelope structure, so that current can be fed in and fed out again in a simple manner. Other arrangements (distributed on both end faces and / or distributed on the circumferential surface) are also possible and are not shown in the drawing.

[0035] exist Figure 5 The representation of FIG. 1 shows a hollow conductor 10 which, on a construction platform 15 , is supported by a support 14 as a minimal support.

[0036] exist Figure 6The presentation in FIG. 4 shows a plurality of hollow conductors manufactured with additive manufacturing. An embodiment in which adjacent channels of the hollow conductors are connected by means of a conical connecting tube is advantageous, which at the same time allows additive manufacturing on the component support on the underside with minimal requirements (this is also the case in FIG. 4 ). Figure 5 ). It can also be advantageous if the additively manufactured resistance wheel can be manufactured in one piece as a long hollow conductor of complex design with elements such as, for example, for the shaft-hub connection, for the flange and for the electrical contact.

[0037] For example, an additively manufactured resistor wheel is filled with unmelted powder in the hollow conductor immediately after its manufacture. Before filling with phase change material, the powder must be completely removed. In very curved and interlaced structures, this can mean very high costs. Therefore, in order to ensure that the removal of powder is as labor-saving as possible, the design advantageously provides a helical arrangement of the hollow conductors, wherein the removal of powder can be performed only by axial rotation of the entire structure. This is the case in Figure 7 Other designs require complex multi-axis motion to perform de-powdering. Figure 7 The structure shown requires both good additive manufacturing (eg, using the axial direction as the build direction) and good powder removal.

[0038] As mentioned above, for the purpose of mechanical stability of the additively manufactured rotor assembly, during operation, at a typical rated speed of, for example, 1800 rpm or 3600 rpm, for example, it is embedded in a pot-like encapsulation structure and the gap is filled with an electrically insulating resin (see for this purpose Figure 4 The resin fulfils the function of insulating the individual channels of the hollow conductor as well as insulating it from the pot-shaped encapsulation structure. For example, the structure is only partially filled with resin (e.g. in sections in the form of a disk), so that air circulation in the remaining area allows the heat to be dissipated in the sense of the above-mentioned effective recooling ( Figure 6 ). An advantage of the additive manufacturing of the rotor components of the invention is that further complex geometric components can be produced in one manufacturing step.

[0039] For example, for better heat dissipation, as in Figure 8 As presented in FIG. 1 , the impeller structure 16 which supplies cooling gas to the rotating structure can also be designed using additive manufacturing.

[0040] In order to optimize the actual function of the component (providing electrical resistance), it is of interest to make the cross-section of the hollow conductor as small as possible, but nevertheless to make the overall structure of the rotor component as strong as possible, in particular since it is a long, multiply folded hollow conductor in which adjacent channels cannot support each other. The structure of the rotor component is therefore subject to flexibility. In order to limit this, the hollow conductor can be reinforced internally, for example by introducing a grid structure which completely or partially fills the volume. In particular, if the grid structure is arranged in the connection area of ​​two adjacent channels of the hollow conductor, the grid structure can advantageously react torque there between the two channels. The grid structure 17 in Fig. 9 Presented in.

Claims

1. A synchronous machine (1) having a starting resistor, wherein: The starting resistor has an electrical conductor whose specific electrical resistance differs from copper, wherein the starting resistor has, in particular, a hollow structure.

2. The synchronous machine (1) according to claim 1, wherein: The specific resistance of the electrical conductor is greater than copper.

3. The synchronous machine (1) according to claim 1 or 2, wherein: The electrical conductor has a lower specific weight than copper.

4. The synchronous machine (1) according to any one of claims 1 to 3, wherein: The starting resistor has a phase change material.

5. The synchronous machine (1) according to any one of claims 1 to 4, wherein: The electrical conductor comprises aluminum or an aluminum alloy.

6. The synchronous machine (1) according to any one of claims 1 to 5, wherein: The electrical conductor has a length which exceeds the size of the starting resistor by a multiple.

7. The synchronous machine (1) according to any one of claims 1 to 6, wherein: The electrical conductor is designed as a hollow conductor.

8. The synchronous machine (1) according to any one of claims 1 to 7, wherein: The electrical conductor is manufactured by additive manufacturing.

9. The synchronous machine (1) according to any one of claims 1 to 8, wherein: The starting resistor is surrounded by a pot-shaped element.

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