Synchronous machine having a starting resistor

Abstract

A synchronous machine (1) has a starting resistor, wherein the starting resistor comprises an electrical conductor the specific electric resistance of which is different from that of copper, and wherein the starting resistor particularly comprises a hollow structure.

Description

[0001] Description

[0002] Synchronous machine with a starting resistor

[0003] The invention concerns a synchronous machine with a starting resistance.

[0004] When starting synchronous machines, a starting resistor can be used as a component in the short-circuited rotor circuit to advantageously increase the starting torque. A so-called "resistance wheel" used for this purpose has a given resistance and a given heat capacity. During the start-up phase and the resulting high current, this absorbs the heat generated by the power loss at the resistor, so that the temperature increase at the resistance wheel remains below a limit determined by the materials used, especially the insulation materials.

[0005] One problem that can arise is that resistance wheels, as rotor components, are made from copper conductors with a very high overall mass. This has a negative impact on both the size and the rotor dynamics of the machine. However, this can be necessary to achieve the required heat capacity. The resistance wheel can be made from a large mass of copper conductor in order to achieve sufficient heat capacity. The copper conductor is arranged in a rotor element in such a way that the required resistance is produced across the cross-section and length of the conductor. For a conventional resistance wheel in a large synchronous machine, this can mean a typical mass of, for example, 400 kg.

[0006] One object of the invention is to design an improved synchronous machine. This object is achieved according to claim 1. Further exemplary embodiments are provided by the dependent claims 2 to 9.

[0007] A synchronous machine has a starting resistance, wherein the starting resistance has an electrical conductor whose specific electrical resistance is different from copper, wherein the starting resistance in particular has a hollow structure. The hollow structure can be open or closed. A medium can be located in the hollow structure. Cooling channels or closed volumes can be formed by means of the hollow structure or hollow structures.

[0008] In one design of the synchronous machine, the specific electrical resistance of the electrical conductor is greater than that of copper. Thus, the resistance value can be increased by choosing a different material.

[0009] In one embodiment of the synchronous machine, the electrical conductor has a lower specific gravity than copper. This has the advantage of lower inertia.

[0010] In one embodiment of the synchronous machine, the starting resistor comprises a phase-change material. The phase-change material can be located in one or a plurality of hollow structures. The phase-change material can absorb thermal energy, particularly in the short term.

[0011] In one embodiment of the synchronous machine, the electrical conductor is made of aluminum or an aluminum alloy. Aluminum is a poor electrical conductor compared to copper, but is lighter than copper.

[0012] In one embodiment of the synchronous machine, the electrical conductor has a length that exceeds the dimensions of the starting resistor by several times. This allows the resistance to be increased further. In one embodiment of the synchronous machine, the electrical conductor is designed as a waveguide. The phase-change material can be permanently encapsulated inside the waveguide.

[0013] In one embodiment of the synchronous machine, the electrical conductor is manufactured additively. This allows complex geometric structures to be easily produced.

[0014] In one embodiment of the synchronous machine, the starting resistor is surrounded by a pot-like element. This pot-like element, which forms a restructure, can accommodate the phase-change material.

[0015] The starting resistor can in principle also be manufactured from a material that is a poor electrical conductor than copper. The use of a material with a correspondingly higher specific electrical resistance than copper leads to a lower mass requirement of this material. However, in practice the total amount of heat to be dissipated is often so high that the heat capacity of the reduced mass is not sufficient to keep the maximum temperature occurring at the resistance wheel below a given limit, so that a hollow structure is necessary. For example, in a synchronous machine a first material with a higher specific resistance than copper, with its resulting lower mass requirement, is combined with a second material embedded in this material, a so-called phase change material. Phase change materials, such as e.g.Paraffins, on the one hand, have a comparatively high heat capacity and, on the other hand, absorb heat energy during the phase change without the temperature increasing further. In principle, both the phase change from solid to liquid and liquid to gas are suitable. The phase change material used can be something that has a corresponding phase change temperature above the maximum ambient temperature and below the permissible temperature limit. A suitable material with a higher specific resistance is, for example, an aluminum alloy, which is also suitable in terms of its heat capacity and, as a lightweight material, also benefits the dynamic properties of the rotor.

[0016] In one embodiment of the synchronous machine, a special design of the resistance wheel can result, which allows the lightweight material to be arranged as a very long conductor in such a way that the longest possible path for the current flow is achieved.

[0017] In one embodiment of the synchronous machine, the conductor is designed as a waveguide, inside which the phase-change material is permanently encapsulated. To simultaneously make the resistance wheel as compact as possible, a design is chosen in which the waveguide occupies as much space as possible within the envelope of the entire resistance wheel. The envelope is, for example, a pot-shaped element.

[0018] The arrangement of a waveguide filled with a phase change material has the advantage, particularly compared to a similarly conceivable arrangement of the conductor within a vessel filled with phase change material, that a large surface is created which can be advantageously used for effective recooling, because the phase change that has taken place must be reversed as quickly as possible in order to enable further starts of the machine.

[0019] In one embodiment of the synchronous machine, this results in a rotor component, for example, a cylindrical envelope of the entire resistance wheel, in which a single waveguide is arranged in a meandering, spiral or other manner in such a way as to save space.

[0020] From these explanations it is clear that the design described above places high demands on the manufacturing processes to be used. On the one hand, a very long waveguide has to be manufactured from a material that is sufficiently strong, lightweight and highly accurate so that the rotational forces can be absorbed and the rotor dynamics are positively influenced overall. On the other hand, the design described above is complex and difficult to implement in terms of manufacturing technology. One option for this is additive manufacturing, in particular laser beam melting, in which a component is produced layer by layer using a laser beam in a powder bed. This makes it possible to implement a high level of geometric complexity, such as that offered by the hollow structures described, while at the same time being flexible compared to a manufacturing process that requires a lot of fixture work.In particular, a special high-strength aluminum alloy can be used for laser beam melting, which particularly well meets the mechanical requirements described above. Additive manufacturing processes are also subject to certain manufacturing constraints. For example, laser beam melting typically does not allow for the creation of structures horizontally in the powder bed due to the physically necessary dissipation of the thermal energy introduced by the laser. Therefore, a predominantly axial arrangement of the waveguide is advantageous.

[0021] The features of the individual claimed or described objects can be readily combined with one another. The invention is illustrated and explained in more detail below using figures as examples. The features shown in the figures can be combined by a person skilled in the art to form new embodiments without departing from the invention.

[0022] Fig 1 a spiral arrangement of a waveguide,

[0023] FIG 2 a meandering arrangement of a waveguide,

[0024] FIG 3 a waveguide with a circular sector-shaped cross-section,

[0025] FIG 4 a pot-shaped element as a restructure, FIG 5 waveguide with a minimal support to a

[0026] Construction platform, FIG 6 an electrical contact of the waveguide,

[0027] FIG 7 an arrangement of a waveguide for improved depowdering,

[0028] FIG 8 Fan elements for cooling and

[0029] FIG 9 a reinforcement of the waveguide by a grid structure and

[0030] The illustration in Figure 1 shows a spiral arrangement of a waveguide 10 from two perspectives: an axial view and a radial view. Axially, relative to the axis 11, several meandering disks are arranged in a row. This results in a cylindrical envelope of the entire resistance wheel, in which a single waveguide is arranged in a meandering, spiral, or other manner as space-saving as possible.

[0031] The illustration in Figure 2 shows a spiral arrangement of a waveguide 10. The meanders are thus wound around the axis 11.

[0032] The illustration in Figure 3 shows a waveguide 10 with a circular sector-shaped cross-section. A space-saving design can also be achieved, for example, by selecting a cross-section in the shape of a circular sector instead of a round cross-section for the waveguide, so that the gaps between adjacent waveguide paths are minimal. At the same time, the waveguide can be arranged so that the resulting rotor component exhibits the lowest possible imbalance.

[0033] The illustration in Figure 4 shows a starting resistor with a pot-shaped element 12, which is attached to the shaft 13. The starting and ending points of the waveguide 10 are located on one of the two end faces of the cylindrical casing, so that current can be easily fed in and out there. Other arrangements (distribution across both end faces and / or across the casing surface) are also possible and are not shown in the figure.

[0034] The illustration according to Figure 5 shows a waveguide 10 which is attached to a construction platform 15 via holder 14 as a minimal support.

[0035] The illustration in Figure 6 shows a large number of additively manufactured waveguides. An advantageous embodiment is one in which adjacent waveguide passages are connected by tapered connecting tubes, which allows additive manufacturing while simultaneously requiring minimal component support on the underside, as is also shown in Figure 5. Furthermore, it can be advantageous for an additively manufactured resistance wheel to be manufactured in one piece as a complex, long waveguide, simultaneously with elements for, for example, a shaft-hub connection, for flanges, and for electrical contact.

[0036] For example, an additively manufactured resistance wheel is still filled with unmelted powder inside the waveguide immediately after its production. Before it can be filled with phase change material, the powder must be completely removed. In a structure that is highly meandering and nested, this can be very complex. In order to ensure that depowdering is as inexpensive as possible, a design is advantageous which provides for a spiral arrangement of the waveguide, in which depowdering can be carried out simply by axially rotating the entire structure. This is shown in Figure 7. Other designs require complex multi-axial movements to carry out depowdering. The simultaneous requirement for good additive manufacturing (e.g.with the axial direction as the construction direction) and good depowdering shows a structure according to Figure For the purpose of mechanical stabilization of the additively manufactured rotor component described above during operation at typical nominal speeds of e.g. 1800 or 3600 rpm, this is embedded, e.g. in a cup-shaped structure and the spaces between are filled with an electrically insulating resin (see Figure 4). The resin fulfills the function of insulating individual paths of the waveguide as well as insulating the cup-shaped structure. The structure is only partially filled with resin, for example (e.g. segmentally in the form of disks), so that air circulation in the remaining areas allows heat to be dissipated (Figure 6) in the sense of the above-mentioned effective recooling.The advantage of additive manufacturing of the rotor component according to the invention is that additional complex geometric components can be manufactured in one manufacturing step.

[0037] For example, impeller structures 16 can also be designed additionally, which supply cooling air to the rotating structure for better heat dissipation, as shown in Figure 8.

[0038] In order to optimise the actual function of the component (to provide electrical resistance), it is interesting to make the cross-section of the waveguide as small as possible, while still designing the entire structure of the rotor component as rigid as possible, particularly since this is a long, multiply folded waveguide in which adjacent passages cannot support each other. The structure of the rotor component is therefore subject to flexibility. To limit this, the waveguide can be reinforced internally, e.g. by introducing a lattice structure that fills the volume completely or partially. The lattice structure can advantageously counteract torsional moments occurring between the passages, particularly if it is provided in the area where two adjacent passages of the waveguide are connected. A lattice structure 17 is shown in Figure 9.

Claims

Patent claims 1. Synchronous machine (1) with a starting resistor, wherein the starting resistor has an electrical conductor whose specific electrical resistance is different from copper, wherein the starting resistor in particular has a hollow structure.

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

3. Synchronous machine (1) according to claim 1 or 2, wherein the electrical conductor has a lower specific gravity than copper.

4. Synchronous machine (1) according to one of claims 1 to 3, wherein the starting resistor comprises a phase change material.

5. Synchronous machine (1) according to one of claims 1 to 4, wherein the electrical conductor comprises aluminum or an aluminum alloy.

6. Synchronous machine (1) according to one of claims 1 to 5, wherein the electrical conductor has a length which exceeds the dimensions of the starting resistor by a multiple.

7. Synchronous machine (1) according to one of claims 1 to 6, wherein the electrical conductor is designed as a waveguide.

8. Synchronous machine (1) according to one of claims 1 to 7, wherein the electrical conductor is additively manufactured.

9. Synchronous machine (1) according to one of claims 1 to 8, wherein the starting resistor is surrounded by a pot-like element.

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