DE102016216083B4 - Fluid-cooled electrical machine - Google Patents

Abstract

Fluid-cooled electrical asynchronous machine (10), comprising - a stator (12), - a rotor (14) rotatably mounted about an axis (A) within the stator (12), a radial air gap between stator (12) and rotor (14) (8), - a housing (18) in which the rotor (14) and the stator (12) are accommodated and - a fluid cooling device (20) with a wet space (22) formed inside the housing (18), in which a cooling fluid (24) circulates at least for wetting and cooling the rotor (14), the rotor (14) having a first fluid guide element (25b-d) on one end face (10a) which extends radially on the rotor (14) in the direction of the stator (12) rejects the cooling fluid flow (24a) from the rotor (14) and prevents it from penetrating the air gap (8), the rotor (14) having a cage winding (15) axially in a laminated core (14a) running winding bars (16) and with short-circuit rings (17) arranged thereon on the end face, and wherein the first fluid guide element (25b-d) is designed in one piece with a short-circuit ring (17), characterized in that the first fluid-guide element (25b-d) as an axial extension (17b, c) or as a radial extension (17d) on the short-circuit ring ( 17) is formed.

Description

The patent application relates to a fluid-cooled electrical machine. With the US 8 692 425 B2 an electrical machine has become known in which, for the directional distribution of a cooling fluid in the interior of the machine, fluid guide elements in the form of oil deflectors are arranged on both end faces of the rotor, which direct a spray oil flow directed radially outward on the rotor onto end windings of the stator winding To a large extent prevent cooling fluid from entering the radial air gap between rotor and stator. The oil deflectors are designed as separate elements and are fastened separately to the rotor with the aid of fastening means.

The US patent U.S. 4,600,848 A also relates to a fluid-cooled machine which, in addition to the short-circuit rings, comprises further rings which are shrunk onto their outer circumferential surface in order to cool the short-circuit rings and are designed as an axial extension of the short-circuit rings. These additional rings also prevent the cooling fluid from entering the air gap between the stator and rotor.

The DE 10 2013 020 331 A1 discloses an electrical asynchronous machine according to the preamble of claim 1. For the defined guidance of a cooling fluid emerging from the rotor shaft, a fluid guide element in the form of a fluid channel is provided in the short-circuit ring, which extends obliquely to the radial and axial direction of the rotor. As a result, the risk of the cooling fluid getting into the air gap of the electrical machine can be kept particularly low.

On the basis of the prior art mentioned, it is the object of the present invention to simplify a fluid-conducting element in a fluid-cooled electrical asynchronous machine of the generic type and thereby make the machine simpler and more cost-effective.

The above-mentioned object is achieved by an electrical machine having the features of patent claim 1. Advantageous embodiments and developments of the invention are specified in the dependent claims.

A fluid-cooled electrical asynchronous machine is thus proposed with a stator, a rotor which is rotatably mounted within the stator about an axis, a radial air gap being formed between the stator and the rotor. The electrical machine further comprises a housing in which the rotor and the stator are accommodated and a fluid cooling device with a wet space formed within the housing in which a cooling fluid circulates at least for wetting and cooling the rotor. In this case, the rotor has a first fluid guide element on one end face, which deflects from the rotor a flow of cooling fluid propagating radially on the rotor in the direction of the stator and prevents it from penetrating the air gap. Furthermore, the rotor has a cage winding with winding bars running axially in a laminated core and with short-circuit rings arranged on the end face, the first fluid-conducting element being designed in one piece with a short-circuit ring. The fluid guide element is designed as an integral area of the short-circuit ring, which keeps a fluid flow directed from radially inside to radially outside on the rotor away from entering the air gap and, if necessary, also deflects it in another direction.

According to the invention it is provided that the first fluid guide element is designed as an axial extension or as a radial extension on the short-circuit ring.

Fluid can be kept away by a radial covering of the air gap by a short-circuit ring, for which purpose only a correspondingly designed radial collar is to be provided, which is preferably arranged at least slightly radially overlapping the stator core.

In this way, in addition to their electrical function, the short-circuit rings can take on a fluid-conducting function when the rotor is cooled. The modification of the short-circuit rings can in particular be accompanied by an increase in the cross section, so that the electrically effective cross section is increased and the electrical resistance is reduced. The cross-sectional enlargement can be designed in such a way that a surface to be wetted by a cooling fluid is also enlarged and, as a result, a more effective removal of heat loss from the rotor is made possible. In addition, the one-piece design of a short-circuit ring with a fluid-conducting element eliminates the need for boundary surfaces that impede heat dissipation, so that improved heat dissipation from the heat source, i.e. the winding bars and the laminated core of the rotor, is achieved, which ultimately leads to an increase in the efficiency and performance of the electrical machine .

According to an advantageous variant, a short-circuit ring can be designed together at least with a one-piece fluid-conducting element as a cast part made of an aluminum or a copper material, in particular also as a cast part off the tool. According to a further development, the winding bars and the short-circuit rings provided on both sides of the rotor can be designed with the fluid guide elements as a common cast part.

Such a proposed axial extension or radial extension can easily be produced by casting. In order to counteract the Coanda effect, the casting radii can be removed from the outer diameter areas of the axial extensions, for example by making small indentations.

According to an advantageous development, a second fluid guide element can be provided, which is arranged stationary to the stator and which, together with the first fluid guide element, forms a fluid guide structure, in particular a sealing arrangement to prevent fluid from penetrating into the air gap. The second fluid guide element can be provided as a separate element and can be fixed directly or indirectly on the stator or on the housing of the electrical machine. Alternatively, the second fluid guide element can also be designed in one piece with a housing wall of the electrical machine. The second fluid guide element can have openings for the fluid circulating in the machine interior to pass through. Alternatively, this can also be made fluid-tight, so that the end windings of the stator winding are not directly covered by the interior cooling and can optionally be cooled by a separate cooling circuit and possibly also with a different cooling medium.

The invention is described below by way of example with reference to the accompanying figure. This shows a fluid-cooled asynchronous machine with partial areas (a) - (d) which differ in particular in the design of the short-circuit ring.

The figure shows in its entirety in a schematic representation a fluid-cooled electrical machine 10 , in particular an internal rotor type asynchronous machine with a stator 12th and with one inside the stator 12th around an axis A. rotatable rotor 14th , being between stator 12th and rotor 14th a radial air gap 8th is trained. Next is a housing 18th provided in which the rotor 14th and the stator 12th are included. The electrical machine includes a fluid cooling device 20th with one inside the case 18th trained wet room 22nd , in which a cooling fluid 24 at least for wetting and cooling the rotor 14th circulates as indicated by the arrows. The inlet of cooling fluid into the wet room 22nd or the interior of the machine takes place through outflow openings 26a in a rotor shaft designed as a hollow shaft 26th , while the outlet of the cooling fluid via one in a cylindrical housing part 18a or in a bearing shield 18b of the housing 18th provided drainage openings 18c he follows. In the usual way, include in the asynchronous machine 10 both the rotor 14th as well as the stator 12th each sheet metal stacks 12a , 14a , with the stator 12th with a stator winding 13th and the rotor 14th with a short-circuit winding 15th or cage winding are executed, which axially in grooves of the rotor laminated core 14a running winding bars 16 and short-circuit rings arranged thereon at the front on both sides 17th having which the winding bars 16 on the front sides 10a , b the machine 10 electrically connect to one another in the circumferential direction. In the present embodiment, the winding bars are 16 and the short-circuit rings 17th produced as a materially coherent area by means of a die-casting process from an aluminum material. Alternatively, the short-circuit rings 17th also as separate elements on the winding bars 16 be postponed.

The asynchronous machine is used for the following explanations 10 in four sub-areas (a) - (d) divided, which is related to the targeted setting of a flow of the cooling fluid 24 regarding the design of the short-circuit rings 17th distinguish. The division made is for explanatory purposes only. It is understandable that due to the rotational symmetry of the rotor 14th and stator 12th around the axis of rotation A. one, in a sub-area (a) - (d) each embodiment shown at least on one end face 10a or 10b or on both ends 10a , b of rotor 14th and stator 12th can be realized.

In sub-area (a), the cooling fluid 24 initially radially out of the rotor shaft 26th exit and move along the rotor 14th towards the stator 12th and the stator winding 13th , especially at the end winding heads. A certain proportion of the cooling fluid can be used 24 in the air gap 8th occur, which on the one hand leads to undesirable drag losses of the electrical machine 10 lead and on the other hand the cooling fluid 24 , in particular a cooling oil can thermally degrade and destroy.

To avoid the ingress of cooling fluid 24 in the air gap 8th points the rotor 14th How this is exemplarily based on the sub-areas ( b ) - (d) is shown on the end faces 10a , 10b each a first, one-piece with a short-circuit ring 17th formed fluid guide element 25b-d on. In particular, the short-circuit ring 17th and the respective fluid guide element 25b-d formed together as a cast part, which applies here to all exemplary embodiments.

As can be seen, the fluid guide element is 25b in the sub-area ( b ) as an axial extension 17b on the short-circuit ring 17th formed and has radially outwardly rising or opening conical lateral surfaces. This causes a radially inside on the extension 17b impinging cooling fluid flow in both radial and axial directions from the rotor 14th distracted or rejected. Furthermore, a second fluid guide element 19b is provided, which is fixed to the stator 12th is arranged and which is shared with the first fluid guide element 25b a fluid guide structure 32b , in particular a sealing arrangement 32b to avoid the penetration of fluid into the air gap 8th trains. The second fluid guide member 19b is as one between the housing 18th and the stator 12th inserted and the axis A. enclosing annular cap preferably made of a plastic, with an open bottom area provided on this axially and optionally also radially overlapping the extension 25b is arranged. One extending radially over the process 25b propagating cooling fluid flow is thus removed from the air gap through the second fluid guide element 19b 8th kept away and can therefore be in the area of the end shield 18b flow back and through the drainage opening provided there 18c the electric machine 10 leave.

The exemplary embodiment shown in sub-area (c) is based on the above explanations on sub-area ( b ) and is only a modification, with only differences being named below. Here is the one on the short-circuit ring 17th provided extension 17c designed to form the fluid guide element 25c with cylindrical surfaces and the second fluid guide element 19c is only fixed on the stator. Also through this, compared to the sub-area ( b ) modified configuration can use the cooling fluid 24 safe from penetration into the air gap 8th be held.

In the embodiment shown with sub-area (d) is on the short-circuit ring 17th now a radial extension 17d for forming the fluid guide element 25d executed. The appendix 17d bridges the air gap 8th and is also close to the end winding of the stator winding located there 13th brought up, so that an entry gap remaining at this position between the rotor 14th and stator 12th is dimensioned as small as possible. Here, too, a second ring-shaped fluid guide element 19d can be provided if necessary, which, as in the other exemplary embodiments, is, however, not mandatory. In the present case, a ring with a U-shaped cross-section is used for this purpose in sub-area (d), which ring is located on the end shield with a radial leg 18b and with a cylindrical section on the end winding 13th supports and with another leg the extension 25d axially engages behind and overlaps this radially. For the passage of the cooling fluid 24 in the direction of the drainage openings 18c Corresponding through openings are provided in the fluid guide element 19d.

Basically, in the explanations covered, the sub-areas (a) - (d) the location of the inlet and outlet openings 18c , 26a of the cooling fluid, the configuration of the second fluid guide elements 19 can be seen independently of the configuration of the first fluid guide element 25, so that a total of numerous combinations, also not specifically addressed here, are possible and accessible to the person skilled in the art.

It is of course also possible to provide an axially as well as radially extending extension on a short-circuit ring.

List of reference symbols

(a) - (d)

Sub-area

8th

Air gap

10

electric machine

10a, b

Front side

12th

stator

12a

Stator laminated core

13th

Stator winding

14th

rotor

14a

Rotor core

15th

Short circuit winding

16

Winding bar

17th

Short-circuit ring

17b-d

Appendix

18th

casing

18a, b

Bearing shield

18c

Drain opening

20th

Fluid cooling device

22nd

Wet room

24

Cooling fluid

25b-d

Fluid guide element

26th

Rotor shaft

26a

Outlet opening

32b-d

Sealing arrangement

A.

Axis of rotation

Claims (4)

Fluid-cooled electrical asynchronous machine (10), comprising - a stator (12), - a rotor (14) rotatably mounted about an axis (A) within the stator (12), a radial air gap between stator (12) and rotor (14) (8), - a housing (18) in which the rotor (14) and the stator (12) are accommodated and - a fluid cooling device (20) with a wet space (22) formed inside the housing (18), in which a cooling fluid (24) circulates at least for wetting and cooling the rotor (14), wherein - the rotor (14) has a first fluid guide element (25b-d) on one end face (10a), which deflects a cooling fluid flow (24a) spreading radially on the rotor (14) in the direction of the stator (12) from the rotor (14) and on prevents penetration into the air gap (8), wherein - the rotor (14) has a cage winding (15) with winding bars (16) running axially in a laminated core (14a) and with short-circuit rings (17) arranged on the end face and wherein - the first The fluid guide element (25b-d) is designed in one piece with a short-circuit ring (17), characterized in that the first fluid-guide element (25b-d) as an axial extension (17b, c) or as a radial extension (17d) on the short-circuit ring (17 ) is trained. Fluid-cooled electrical machine 10 after Claim 1 , characterized in that a short-circuit ring (17) is formed together as a cast part at least with the first fluid guide element (25). Fluid-cooled electrical machine 10 after Claim 1 or 2 , characterized in that a second fluid guide element (19b-d) is provided, which is arranged in a stationary manner to the stator (12) and which, together with the first fluid guide element (25b-d), has a fluid guide structure (32b-d), in particular a sealing arrangement, to avoid a penetration of cooling fluid (24) into the air gap (8) forms. Fluid-cooled electrical machine 10 according to one of the Claims 1 - 3 , characterized in that the fluid guide structure (32b-d) forms a sealing arrangement in which the short-circuit ring (17) with the first fluid guide element (25b-d) and the second fluid guide element (19b-d) overlap radially and axially.

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