Electric machine with improved slip ring, especially for compressors and mills

Abstract

Electric machine with a stator (1), a rotatably mounted rotor (2) arranged in the stator (1), which has electrical windings (3), a slip ring (4), and a cylindrical element (5) which has a cylindrical diameter (6), wherein the slip ring (4) is electrically connected to the electrical windings (3) and has a slip ring diameter (7), and wherein the rotor (2) is arranged radially outside on the lateral surface of the cylindrical element (5), wherein the slip ring diameter (7) is smaller than the cylinder diameter (6), characterized in that the cylindrical element (5) tapers towards one of its axial ends, wherein the cylindrical element (5) is supported at this axial end, and wherein the slip ring (4) is arranged in the axial region of the tapering (9) of the cylindrical element (5).

Description

[0001] The invention relates to an electrical machine comprising a stator, a rotatably mounted rotor arranged in the stator, which rotor has electrical windings, a slip ring, and a cylindrical element having a cylindrical diameter. The slip ring is electrically connected to the electrical windings and has a slip ring diameter. The rotor is arranged radially outwardly on the lateral surface of the cylindrical element. Furthermore, the invention relates to a compressor or a mill having such an electrical machine.

[0002] The market demands low-speed, high-torque synchronous motors, for example, for ore mills or compressors. These types of machines are characterized, among other things, by the large diameter of the rotating rotor parts.

[0003] In these solutions, the rotor consists of the actual driven shaft and the electrically active rotor parts. The electrical excitation of such machines is achieved via large-diameter slip rings. The slip ring is typically located in or near the axial area of ​​the rotor and stator to keep the slip-ring line between the pole winding and the slip ring as short as possible.

[0004] Such an electric machine, used in a tube mill, is known, for example, from DE 35 27 293 A1. The electric machine comprises a stator and a rotor located therein, which is arranged on a tubular drum of the tube mill and has rotor windings. The rotor windings can be supplied with electrical power by means of slip rings mounted radially on the outside of the drum.

[0005] WO 2011 / 000048 A1 discloses a mill for grinding or comminuting bulk materials and minerals. The mill is a continuously operating centrifugal mill with internal circulation, comprising a main rotor supporting a grinding chamber as a secondary rotor, the axis of rotation of which is substantially parallel to the axis of the main rotor.

[0006] A mill drum is known from DE 11 31 073 A. A pulse generator is attached to the mill drum as a transducer. Its connecting contacts are conductively connected to two slip rings via cables. To reduce the weight and wear of the slip rings, the slip rings are arranged near the mill neck bearing.

[0007] US Pat. No. 5,894,998 A discloses an agitator mill for grinding flowable material. It comprises a stationary, outer, cylindrical grinding vessel, to which a cylindrical inner stator is attached coaxially and at a distance. A rotating, pot-shaped rotor is arranged coaxially with the grinding vessel and engages in the grinding chamber formed between the grinding vessel and the inner stator, so that the grinding chamber is divided into an outer grinding chamber and an inner grinding chamber. The grinding chambers are hydraulically connected to each other via a connecting section.

[0008] The invention is based on the object of improving known electrical machines with slip rings.

[0009] This object is achieved by an electrical machine of the type mentioned above with features according to claim 1. The slip ring diameter is smaller than the cylinder diameter. Furthermore, this object is achieved by a compressor or a mill with such an electrical machine.

[0010] Because the slip ring diameter is smaller than the cylinder diameter, the production of such a slip ring is comparatively simple and inexpensive. Particularly in large, powerful electrical machines such as those used in compressors or mills, especially tube mills, the slip ring no longer needs to be segmented, but can be designed as a single component. Such powerful machines, for example, have an electrical output of several megawatts, in particular more than 10 MW. The relatively small diameter of the slip ring, which is not segmented, makes it comparatively easy to meet high requirements for dimensional accuracy, particularly with regard to concentricity and axial runout, so that manufacturing costs are very low.

[0011] Compared to conventional electrical machines, in which the slip ring diameter is at least as large as the cylinder diameter, the slip ring according to the invention can transmit the same electrical excitation power, but with a lower material usage leading to a significant reduction in component costs.

[0012] The assembly of such a slip ring also offers advantages. For example, the slip ring can be "threaded" onto a corresponding component of the electrical machine and secured to the component in a single step. Compared to segmented slip rings in particular, this eliminates the steps of attaching several individual segments, for example, to the cylindrical element and then aligning them very precisely to meet dimensional accuracy requirements. Any necessary rework, such as grinding or removing material from the slip ring to ensure sufficiently precise concentricity of the slip ring, can thus be completely eliminated.

[0013] The stator and rotor are arranged in the same axial region of the electric machine. To ensure that the slip ring diameter is smaller than the cylinder diameter, the slip ring can be arranged in a different axial region than the rotor and stator, for example. Particularly when the stator and rotor are enclosed by a protective housing, this offers the advantage of reducing the axial space required for such a protective housing, simplifying the machine design and creating more design flexibility.

[0014] If the electric machine is used in a mill, the cylindrical element can be designed as the mill's drum. The material to be ground can be ground in the drum, which has a diameter equal to the cylinder's diameter. The rotor, including its electrical windings, is arranged radially on the outside of the drum's surface, and the slip ring is mounted on a rotating part of the electric machine with a smaller diameter.

[0015] The slip ring can be designed in such a way that several electrical phases can be transferred, for example by the slip ring having several electrical busbars that are electrically insulated from one another and led to the electrical windings.

[0016] In an advantageous embodiment of the invention, the cylindrical element tapers towards one of its axial ends, wherein the cylindrical element is mounted at this axial end, and wherein the slip ring is arranged in the axial region of the bearing or the taper of the cylindrical element.

[0017] The tapered cylindrical element is thus mounted at this axial end, although one or more additional bearings can be provided elsewhere. The arrangement of the slip ring in the axial region of the bearing or the taper has the advantage that the electric machine requires neither more installation space in the radial direction nor more installation space in the axial direction, because such a taper is typically determined by the purpose of the electric machine and not by an improvement in the slip ring. In particular, it allows the use of a slip ring with a particularly small diameter, so that the cost savings are particularly significant, for example due to the reduced material expenditure compared to larger, particularly segmented slip rings. The desired dimensional accuracy can be achieved particularly easily using a slip ring with such a small diameter.

[0018] Particularly in a mill, the tapered portion of the cylindrical element can be designed as an inlet or outlet opening for the material to be ground, which typically has the smallest diameter of all rotating parts. If the provision of the slip ring in the area of ​​the smallest diameter of the cylindrical element results in an increase in the axial length of the mill, it can also be arranged at the tapered portion of the cylindrical element in such a way that the slip ring has the smallest possible slip ring diameter while simultaneously not increasing the axial length of the mill.

[0019] It is conceivable for the cylindrical element to have an axial region with a constant diameter that is equal to the cylinder diameter, and for it to have a further axial region towards the above-mentioned axial end, in which the diameter decreases and which thus represents the taper. Equivalently, it is also conceivable for the cylindrical element to have only a single diameter in the axial direction that is equal to the cylinder diameter, and for the taper to be designed as a separate component that is connected to the cylindrical element and adjoins the cylindrical element in an axial extension at its above-mentioned axial end. For example, such a taper can be designed as a flange, in particular a fastening flange.

[0020] In a further advantageous embodiment of the invention, the electric machine has at least one brush which contacts the slip ring and by means of which the electrical windings of the rotor can be supplied with electrical power via the electrical connection, wherein the slip ring and the at least one brush are at least partially enclosed by a first housing.

[0021] The first housing reliably protects the slip ring and at least one brush from adverse environmental influences, extending the service life of the slip ring and at least one brush. This is particularly advantageous in mills, where dust and debris could otherwise penetrate the electrical machine and damage it.

[0022] The first housing can, for example, have a first sealing element, for example in the form of a first sealing ring, which closes the transition between rotating parts and stationary parts of the electrical machine at least for small pieces of rock, in particular for dust and splash water. Furthermore, it can be provided that the electrical connection of the slip ring to the electrical windings is passed through the first housing and is electrically insulated from the first housing. In particular, if the cylindrical element has a taper and the slip ring is arranged at the same axial end of the cylindrical element as the taper, the electrical connection can be fastened radially outwardly to the taper, wherein the electrical connection is electrically insulated from the taper.

[0023] In particular, when several electrical phases are transmitted by means of the slip ring and therefore several busbars are present, a corresponding number of brushes are also provided, whereby the entire arrangement is still at least partially enclosed by the first housing.

[0024] In a further advantageous embodiment of the invention, the stator and the rotor are at least partially enclosed by a second housing, wherein the electrical connection is led into the second housing in an electrically insulated manner from the second housing, wherein the electrical connection is insulated from the second housing.

[0025] The second housing allows the stator and the rotor, especially the electrical windings of the rotor, to be reliably protected from adverse environmental influences, which in turn extends the service life of the electrical machine and is of great advantage, especially in mills due to their particularly adverse environmental influences.

[0026] The second housing can in turn have a second sealing element, for example in the form of a second sealing ring, which closes the transition between rotating parts and stationary parts of the electrical machine at least for smaller rock fragments, in particular for dust and splash water.

[0027] In a further advantageous embodiment of the invention, the cylindrical element is at least partially hollow cylindrical and has an opening at least at one of its axial ends.

[0028] The hollow cylindrical part of the cylindrical element can, for example, be the drum of a mill, wherein the opening can be provided for the supply or removal of the ground material.

[0029] The invention is described and explained in more detail below with reference to the exemplary embodiments shown in the figures. They show: Fig. 1 an electric machine of a tube mill according to the state of the art, Fig. 2 and Fig. 3 an embodiment of the electrical machine according to the invention.

[0030] Fig. 1 shows an electrical machine of a tube mill according to the prior art. The electrical machine has a stator 1, in which a rotor 2 with electrical windings 3 is arranged coaxially to the stator 1, wherein the rotor 2 is arranged radially outward on a cylindrical element 5 of the mill. The electrical windings 3 of the rotor 2 are connected to a slip ring 4 by means of an electrical connection 11, wherein the slip ring 4 is electrically insulated from the cylindrical element 5 and is connected to it in a rotationally fixed manner on its radial outer surface. Thus, the cylindrical element 5 has a cylinder diameter 6 and the slip ring 4 has a slip ring diameter 7, wherein the slip ring diameter 7 is larger than the cylinder diameter 6. Electrical power can be supplied to the rotor 2 via brushes 10, which are in electrical contact with the slip ring 4.Particularly in large electrical machines, which are used for example in compressors or mills, the slip ring 4 is often designed in segments.

[0031] Fig. 2 shows a further embodiment of an electrical machine. The electrical machine has a stator 1 and a rotor 2 arranged concentrically to the stator 1 and within the stator 1, wherein the rotor 2 is arranged radially outward on a cylindrical element 5 which has a cylinder diameter 6. The stator 2 has electrical windings 3 which are connected to a slip ring 4 by means of an electrical connection 11, wherein the slip ring 4 has a slip ring diameter 7 which is smaller than the cylinder diameter 6. Furthermore, a brush 10 is provided which is in contact with the slip ring 4 so that electrical power can be supplied to the electrical windings 3 of the rotor 2 via the brush 10, the slip ring 4 and the electrical connection 11.

[0032] Fig. Figure 3 shows an embodiment of the electrical machine according to the invention. The same reference numerals as in Fig. 2 identical items.

[0033] The cylindrical element 5 has a taper 9 at its axial end shown. In the area of ​​the taper 9, a first housing 12 is arranged, in which the slip ring 4 is accommodated, the slip ring diameter 7 of which is significantly smaller than the cylinder diameter 6. In Fig. 3, the slip ring 4 is shown as having busbars for three electrical phases. Also located in the first housing 12 are three brushes 10, which are in contact with the respective busbar of the slip ring 4. The first housing 12 at least partially encloses the slip ring 4 and the brushes 10, with a first sealing element 15, for example in the form of one or more sealing rings, being provided between the rotatable and stationary parts of the first housing 12. Thus, the first housing 12 offers the slip ring 4 and the brushes 10 reliable protection against adverse environmental influences.

[0034] The rotor 2 and the stator 1 are arranged in a second housing 13, which at least partially encloses them. A second sealing element 16 is provided between the rotating and stationary parts, which can be designed as one or more sealing rings. The second housing 13 protects the electrical windings 3, the rotor 2, and the stator 1 from adverse environmental influences.

[0035] To supply the electrical windings 3 of the rotor 2, the electrical connection 11 is passed through the first housing 12, wherein the electrical connection 11 is electrically insulated from the first housing 12. The electrical connection 11 is then guided to the rotor 2 and is attached to the radial outer side of the taper 9 by means of a support element 17, wherein the electrical connection 11 is electrically insulated from the taper 9.

[0036] The cylindrical element 5 is mounted at the axial end where the taper 9 is also located, by means of a bearing 8. The cylindrical element 5 is designed as a hollow cylinder and the taper 9 as a rotationally symmetrical hollow body, so that the cylindrical element 5 has an opening 14 in the axial direction.

[0037] In the event that the electric machine is used in a mill, in particular a tube mill, and the cylindrical element 5 is the drum of the mill, the material to be ground can be introduced and / or removed through the opening 14.

[0038] In summary, the invention relates to an electrical machine comprising a stator, a rotatably mounted rotor arranged in the stator, which rotor has electrical windings, a slip ring, and a cylindrical element having a cylinder diameter, wherein the slip ring is electrically connected to the electrical windings and has a slip ring diameter, and wherein the rotor is arranged radially outwardly on the lateral surface of the cylindrical element. Furthermore, the invention relates to a compressor or a mill having such an electrical machine. In order to improve known electrical machines with slip rings, it is proposed that the slip ring diameter be smaller than the cylinder diameter.

Claims

[1] Electric machine with a stator (1), a rotatably mounted rotor (2) arranged in the stator (1) and having electrical windings (3), a slip ring (4), and a cylindrical element (5) having a cylinder diameter (6), wherein the slip ring (4) is electrically connected to the electrical windings (3) and has a slip ring diameter (7), and wherein the rotor (2) is arranged radially outwardly on the lateral surface of the cylindrical element (5), wherein the slip ring diameter (7) is smaller than the cylinder diameter (6), characterized by that the cylindrical element (5) tapers towards one of its axial ends, wherein the cylindrical element (5) is mounted at said axial end, and wherein the slip ring (4) is arranged in the axial region of the taper (9) of the cylindrical element (5). [2] Electrical machine according to claim 1, wherein the electric machine has at least one brush (10) which contacts the slip ring (4) and by means of which the electrical windings (3) of the rotor (2) can be supplied with electrical power via the electrical connection (11), and wherein the slip ring (4) and the at least one brush (10) are at least partially enclosed by a first housing (12). [3] Electrical machine according to one of the preceding claims, wherein the stator (1) and the rotor (2) are at least partially enclosed by a second housing (13), and wherein the electrical connection (11) is guided into the second housing (13) in an electrically insulated manner, wherein the electrical connection (11) is insulated from the second housing (13). [4] Electrical machine according to one of the preceding claims, wherein the cylindrical element (5) is at least partially hollow-cylindrical and has an opening (14) at least at a first of its axial ends. [5] Electrical machine according to one of claims 2 to 4, wherein a first sealing element (15) is provided between rotatable and stationary parts of the first housing (12). [6] Electrical machine according to one of claims 3 to 5, wherein a second sealing element 16 is provided between rotatable and stationary parts of the second housing (13), [7] Compressor or mill with an electric machine according to one of the preceding claims.

Images