AU2012391128B2

AU2012391128B2 - Electric machine comprising an improved slip ring, particularly for compressors and mills

Info

Publication number: AU2012391128B2
Application number: AU2012391128A
Authority: AU
Inventors: Horst Kummlee; Christian Schiller
Original assignee: Innomotics GmbH
Current assignee: Innomotics GmbH
Priority date: 2012-09-26
Filing date: 2012-09-26
Publication date: 2017-04-06
Anticipated expiration: 2032-09-26
Also published as: DE112012006939A5; AU2012391128A1; WO2014048466A1

Abstract

The invention relates to an electric machine that comprises a stator (1), a rotor (2) rotatably mounted and arranged in said stator (1) and having electrical windings (3), a slip ring (4), and a cylinder-shaped element (5) that has a cylindrical diameter (6), said slip ring (4) being electrically connected to the electrical windings (3) and having a slip ring diameter (7), and said rotor (2) being radially arranged externally on the lateral surface of the cylinder-shaped element (5). The invention also relates to a compressor or a mill that comprises such an electric machine. In order to improve known electric machines comprising slip rings (4), it is suggested that the slip ring diameter (7) is smaller than the cylindrical diameter (6).

Description

1 2012391128 15 Feb 2017

Description

ELECTRIC MACHINE COMPRISING AN IMPROVED SLIP RING, PARTICULARLY FOR COMPRESSORS AND MILLS

The invention relates to an electric machine comprising a stator, a rotor rotatably mounted and arranged in the stator and having electrical windings, a slip ring, and a cylindershaped element which has a cylindrical diameter, said slip ring being electrically connected to the electrical windings and having a slip ring diameter, and said rotor being radially arranged externally on the lateral surface of the cylinder-shaped element. The invention furthermore relates to a compressor or a mill comprising such an electric machine.

The market requires slowly running synchronous motors having a high torque, for example for ore mills or compressors. These types of machines are characterized inter alia by a large diameter of the rotating rotor parts.

In these approaches the rotor consists of the actual shaft to be driven and the electrically active rotor parts. The electrical excitation of such machines is effected by way of slip rings having a large diameter. The slip ring is normally arranged in or in the vicinity of the axial region of the rotor and of the stator in order to configure the slip ring line between pole winding and slip ring as short as possible.

Such an electric machine, employed in a tube mill, is known for example from DE 35 27 293 Al. The electric machine has a stator and a rotor situated 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 fitted radially externally on the drum.

In a first aspect the present invention provides an electric machine comprising a stator, a rotor rotatably mounted and arranged in the stator and having electrical windings, a slip ring, and a cylinder-shaped element which has a cylindrical diameter, wherein the slip ring is electrically connected to the electrical windings and has a slip ring diameter, and wherein the rotor is radially arranged externally on the lateral surface of the cylinder-shaped element, wherein the slip ring diameter is smaller than the cylindrical diameter.

AH26(12588538_2):JBL 2 2012391128 15 Feb 2017

As a result of the fact that the slip ring diameter is smaller than the cylindrical diameter, the manufacture of such a slip ring may be comparatively simple and cost-effective. In particular in the case of large and powerful electric machines which are employed in compressors or mills, in particular tube mills, the slip ring may thus no longer need to be embodied in segmented form but may be embodied as a single component. Such powerful machines have for example an electrical output of several megawatts, in particular more than 10 MW. As a result of the slip ring having a comparatively small diameter, which preferably is not segmented, strict requirements in terms of accuracy of shape, in particular in respect of radial and axial running, may be met comparatively simply, which means that the manufacturing costs may be very favorable.

In comparison with the conventional electric machines in which the slip ring diameter is at least the same size as the cylindrical diameter, the slip ring according to an embodiment of the invention may transfer the same electrical exciter power, in which case a reduced material requirement however may result in a considerable reduction in the component costs.

The assembly of an embodiment of a slip ring also offers advantages. For example, the slip ring may be "threaded" onto a corresponding component of the electric machine in a single work step and secured on the component. In particular compared with segmented slip rings the work steps associated with securing a plurality of individual segments for example on the cylinder-shaped element and subsequently aligning said segments very accurately in order to meet the requirements in respect of accuracy of shape are thus dispensed with. Any necessary reworking, such as for example grinding or machining material from the slip ring in order to ensure a sufficiently precise radial running of the slip ring, may thus be completely dispensed with.

In an embodiment, the stator and the rotor are arranged in the same axial region of the electric machine. In order that the slip ring diameter is smaller than the cylindrical diameter the slip ring can be arranged for example in a different axial region than the rotor and the stator. In particular, if the stator and the rotor are enclosed by a protective housing, thereby the axial installation space required for such a protective housing may be reduced, which means that the machine design is simplified and more design freedom results.

AH26(12588538_2):JBL 3 2012391128 15 Feb 2017

If an embodiment of the electric machine is employed in a mill then the cylinder-shaped element may be embodied as the drum of the mill. The mill charge may be milled in the drum which has the diameter of the cylindrical diameter. The rotor together with its electrical windings is arranged radially externally on the lateral surface of the drum and the slip ring is arranged on a rotating part of the electric machine having a smaller diameter.

In this situation the slip ring may be embodied such that a plurality of electrical phases can be transferred, for example by means of the fact that the slip ring has a plurality of electrical busbars which, electrically isolated from one another, are connected to the electrical windings.

In a preferable embodiment of the invention, the cylinder-shaped element tapers to one of its axial ends, with the cylinder-shaped element being mounted at this axial end, and with the slip ring being arranged in the axial region of the mounting or of the taper of the cylindershaped element.

The tapering cylinder-shaped element is thus mounted at this axial end, in which case a further mounting or a plurality of further mountings can also be provided elsewhere. The arrangement of the slip ring in the axial region of the mounting or of 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 of the slip ring. In particular, a slip ring having a particularly small diameter may thus be employed, which means that the cost savings for example resulting from the reduced material consumption in comparison with larger, in particular segmented, slip rings are particularly significant. A desired accuracy of shape may be achieved particularly effortlessly by means of a slip ring having such a small diameter.

In particular with regard to a mill the taper of the cylinder-shaped element may be embodied as an inlet or outlet opening for the mill charge, which usually has the smallest diameter of all the rotatable parts. In the event that the provision of the slip ring in the region of the smallest diameter of the cylinder-shaped element results in an increase in the overall axial length of the mill, provision may also be made to arrange the slip ring in such a manner on the taper of the cylinder-shaped element that the slip ring has as small a slip ring diameter as possible and at the same time the overall axial length of the mill is not increased.

AH26(12588538_2):JBL 4 2012391128 15 Feb 2017

It is conceivable in this situation that the cylinder-shaped element has an axial region having a constant diameter which is equal to the cylindrical diameter and has a further axial region towards the aforementioned axial end in which that diameter reduces and which thereby constitutes the taper. In an equivalent manner thereto it is also conceivable that the cylindershaped element only has a single diameter in the axial direction which is equal to the cylindrical diameter, and the taper is embodied as a separate component which is connected to the cylindershaped element and follows the cylinder-shaped element in an axial extension at the aforementioned axial end thereof. For example, such a taper may be embodied as a flange, in particular a mounting flange.

In a further preferable 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 by way of the electrical connection, with the slip ring and the at least one brush being at least partially enclosed by a first housing.

The slip ring and the at least one brush may be reliably protected by the first housing against adverse environmental influences, whereby the service life of the slip ring and the at least one brush can be extended. This is a major advantage particularly in the case of mills because dust and rock fragments could there otherwise penetrate into the electric machine and could damage said electric machine.

The first housing may for example have a first sealing element, for example in the form of a first sealing ring, which seals the transition between rotatable parts and fixed parts of the electric machine at least for smaller rock fragments, particularly for dust and splash water. Provision may furthermore be made that the electrical connection between the slip ring and the electrical windings is taken through the first housing and is electrically isolated from the first housing in this situation. In particular when 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 may be secured radially externally on the taper, with the electrical connection being electrically isolated from the taper.

AH26(12588538_2):JBL 5 2012391128 15 Feb 2017

In particular when a plurality of electrical phases are transferred by means of the slip ring and therefore a plurality of busbars are present, a corresponding number of brushes are also provided, with the entire arrangement still at least partially being enclosed by the first housing.

In a further preferable embodiment of the invention, the stator and the rotor are at least partially enclosed by a second housing, wherein the electrical connection is taken into the second housing electrically isolated from the second housing, wherein the electrical connection is isolated from the second housing.

The stator and the rotor, in particular the electrical windings of the rotor, may be reliably protected by the second housing against adverse environmental influences, which in turn extends the service life of the electric machine and is a major advantage particularly in the case of mills on account of their particularly adverse environmental influences.

The second housing may in turn have a second sealing element, for example in the form of a second sealing ring, which seals the transition between rotatable parts and fixed parts of the electric machine at least for smaller rock fragments, particularly for dust and splash water.

In a further preferable embodiment of the invention, the cylinder-shaped element is at least partially hollow-cylinder-shaped and has an opening at least at one of its axial ends.

The hollow-cylinder-shaped part of the cylinder-shaped element may for example be the drum of a mill, wherein the opening can be provided for delivery or discharge of the mill charge.

Preferred embodiments of the present invention will now be described, by way of examples only, with reference to the accompanying drawings: FIG 1 shows an electric machine of a tube mill according to the prior art, FIG 2 shows a first embodiment of the electric machine according to the invention, and

The specification continues on page 7

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PCT/EP2012/068979 / 2012P06539WOAU 6

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 taken into the second housing electrically isolated from the second housing, wherein the electrical connection is isolated from the second housing.

The stator and the rotor, in particular the electrical windings of the rotor, can be reliably protected by the second housing against adverse environmental influences, which in turn extends the service life of the electric machine and is a major advantage particularly in the case of mills on account of their particularly adverse environmental influences.

The second housing can in turn have a second sealing element, for example in the form of a second sealing ring, which seals the transition between rotatable parts and fixed parts of the electric machine at least for smaller rock fragments, particularly for dust and splash water.

In a further advantageous embodiment of the invention, the cylinder-shaped element is at least partially hollow-cylindershaped and has an opening at least at one of its axial ends.

The hollow-cylinder-shaped part of the cylinder-shaped element can for example be the drum of a mill, wherein the opening can be provided for delivery or discharge of the mill charge.

The invention will be described and explained in detail in the following with reference to the exemplary embodiments illustrated in the figures. In the drawings: FIG 1 shows an electric machine of a tube mill according to the prior art, FIG 2 shows a first embodiment of the electric machine according to the invention, and

PCT/EP2012/068979 / 2012P06539WOAU 7 FIG 3 shows a second embodiment of the electric machine according to the invention.

Figure 1 shows an electric machine of a tube mill according to the prior art. The electric machine has a stator 1, in which a rotor 2 having electrical windings 3 is arranged coaxially with the stator 1, with the rotor 2 being arranged radially externally on a cylinder-shaped element 5 of the mill. The electrical windings 3 of the rotor 2 are connected by means of an electrical connection 11 to a slip ring 4, with the slip ring 4 being electrically isolated from the cylinder-shaped element 5 and in this case being connected to the latter in rotationally fixed fashion on the radial outer surface thereof. The cylinder-shaped element 5 thus has a cylindrical diameter 6 and the slip ring 4 has a slip ring diameter 7, where the slip ring diameter 7 is greater than the cylindrical diameter 6. Electrical power can be delivered to the rotor 2 by way of brushes 10 which are in electrical contact with the slip ring 4. In particular in the case of large electric machines which are employed for example in compressors or mills the slip ring 4 is often embodied in segmented form.

Figure 2 shows a first embodiment of the electric machine according to the invention. The electric machine has a stator 1 and a rotor 2 arranged concentrically with respect to the stator 1 and inside the stator 1, with the rotor 2 being arranged radially externally on a cylinder-shaped element 5 which has a cylindrical diameter 6. The stator 2 has electrical windings 3 which are connected by means of an electrical connection 11 to a slip ring 4, with the slip ring 4 having a slip ring diameter 7 which is smaller than the cylindrical diameter 6. Furthermore, a brush 10 is provided which is in contact with the slip ring 4, which means that electrical power can be delivered to electrical windings 3 of the rotor 2 by way of the brush 10, the slip ring 4 and the electrical connection 11.

PCT/EP2012/068979 / 2012P06539WOAU 8

Figure 3 shows a second embodiment of the electric machine according to the invention, where the same reference characters as in Figure 2 identify the same objects.

The cylinder-shaped element 5 exhibits a taper 9 at its illustrated axial end. In the region of the taper 9 is arranged a first housing 12 in which the slip ring 4 is accommodated, the slip ring diameter 7 of which is considerably smaller than the cylindrical diameter 6. In Figure 3 the slip ring 4 is illustrated such that it has busbars for three electrical phases. Likewise situated 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 encloses the slip ring 4 and the brushes 10 at least partially, with a first sealing element 15, for example in the form of one sealing ring or a plurality of sealing rings, being provided between rotatable and stationary parts of the first housing 12. The first housing 12 thus affords the slip ring 4 and the brushes 10 reliable protection against adverse environmental influences.

The rotor 2 and the stator 1 are arranged in a second housing 13 which at least partially encloses them both. In this situation a second sealing element 16 is provided between rotatable and stationary parts which in turn can be embodied as one sealing ring or a plurality of sealing rings. The second housing 13 in this case protects the electrical windings 3, the rotor 2 and the stator 1 against adverse environmental influences.

In order to supply the electrical windings 3 of the rotor 2 the electrical connection 11 is taken through the first housing 12, with the electrical connection 11 being electrically isolated from the first housing 12. The electrical connection 11 is subsequently taken to the rotor 2 and is secured on the radial outer surface of the taper 9 by means of a support element 17, with the electrical connection 11 being electrically isolated from the taper 9.

PCT/EP2012/068979 / 2012P06539WOAU 9

The cylinder-shaped element 5 is mounted by means of a mounting 8 at that axial end where the taper 9 is also arranged. Here the cylinder-shaped element 5 is embodied as a hollow cylinder and the taper 9 as a rotationally symmetrical hollow body, which means that the cylinder-shaped element 5 has an opening 14 in the axial direction.

In the event that the electric machine is employed in a mill, in particular a tube mill, and the cylinder-shaped element 5 is the drum of the mill, the mill charge can be introduced and/or discharged through the opening 14.

To summarize, the invention relates to an electric machine comprising a stator, a rotor rotatably mounted and arranged in the stator and having electrical windings, a slip ring, and a cylinder-shaped element which has a cylindrical diameter, said slip ring being electrically connected to the electrical windings and having a slip ring diameter, and said rotor being radially arranged externally on the lateral surface of the cylinder-shaped element. The invention furthermore relates to a compressor or a mill comprising such an electric machine. In order to improve known electric machines comprising slip rings it is proposed that the slip ring diameter is smaller than the cylindrical diameter.

Claims

1. An electric machine comprising a stator, a rotor rotatably mounted and arranged in the stator and having electrical windings, a slip ring, and a cylinder-shaped element which has a cylindrical diameter, wherein the slip ring is electrically connected to the electrical windings and has a slip ring diameter, and wherein the rotor is radially arranged externally on the lateral surface of the cylinder-shaped element, wherein the slip ring diameter is smaller than the cylindrical diameter.

2. The electric machine as claimed in claim 1, wherein the cylinder-shaped element tapers to one of its axial ends, wherein the cylinder-shaped element is mounted at this axial end, and wherein the slip ring is arranged in the axial region of the mounting or of the taper of the cylinder-shaped element.

3. The electric machine as claimed in any one of the preceding claims, wherein 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 by way of the electrical connection, and wherein the slip ring and the at least one brush are at least partially enclosed by a first housing.

4. The electric machine as claimed in any one of the preceding claims, wherein the stator and the rotor are at least partially enclosed by a second housing, and wherein the electrical connection is taken into the second housing electrically isolated, wherein the electrical connection is isolated from the second housing.

5. The electric machine as claimed in any one of the preceding claims, wherein the cylinder-shaped element is at least partially hollow-cylinder-shaped and has an opening at least at a first of its axial ends.

6. A compressor or mill comprising the electric machine as claimed in any one of the preceding claims.