ENCAPSULED ELECTRIC MACHINE WITH EXTERNAL LIQUID COOLING CIRCUIT

Description

[0001] The present invention relates to an electric machine, wherein the electric machine has a rotor and a stator, wherein the rotor is rotatable about an axis of rotation of the electric machine, wherein, viewed around the axis of rotation, the rotor is surrounded by the stator and the stator is surrounded by an outer shell, wherein the outer shell extends in the direction of the axis of rotation from a front end face to a rear end face, such that the front and rear end faces and the stator define an interior region containing the rotor, and the front and rear end faces, the stator, and the outer shell define an exterior region radially surrounding the interior region, wherein the interior region and the exterior region are interconnected by means of openings, so that air can flow from the interior region into the exterior region and from there back into the interior region, wherein axially extending tubes are attached in the front and rear end faces, respectively.so that the axially running tubes extend from the front end piece, across the outer surface, to the rear end piece.

[0002] In some applications, the electrical machines used must be encapsulated with explosion protection type Ex d. However, such electrical machines are also required in increasingly larger sizes.

[0003] In larger versions of such electrical machines, the electrical components are often designed as described above. These electrical machines are air-cooled. For this purpose, a fan is mounted on one of the two end faces, on the side facing away from the outer casing. This fan blows cooling air through the axially running tubes for secondary cooling.

[0004] Air is a relatively poor cooling medium. It would be better to be able to cool the electric machine using a liquid cooling medium – especially water – as part of secondary cooling.

[0005] An electrical machine of the type mentioned above is known, for example, from US 3,457,439 A or CN 101,938,191 A. Such an electrical machine can also be found in WO 2016 / 008 709 A1.

[0006] The object of the present invention is to create an electric machine of the type mentioned above which is cooled with a liquid cooling medium.

[0007] The problem is solved by an electric machine with the features of claim 1. Advantageous embodiments of the electric machine are the subject of dependent claims 2 to 10.

[0008] According to the invention, an electrical machine of the type mentioned above is designed by: that a front and a rear end element are attached to the front and rear end sections on their respective sides facing away from the outer shell in a liquid-tight manner, so that the front end section and the front end element enclose a front cavity and the rear end section and the rear end element enclose a rear cavity, that the axially extending pipes open into the front and rear cavities, that the front cavity is divided into at least two sub-areas by means of a partition, that a portion of the axially extending pipes opens into one of the sub-areas and another portion of the axially extending pipes opens into another of the sub-areas, that a connection for supplying the liquid coolant is arranged in one sub-area and that the connection for discharging the liquid coolant is arranged in the other sub-area.The front and rear end plates and the outer casing encapsulate the rotor and stator in a type of ignition protection.

[0009] The at least two sections are separated from each other by a liquid-tight partition. The front cavity is liquid-tight, except for the connections for supplying and discharging the liquid cooling medium and the access points to the axially running pipes. The rear cavity is liquid-tight, except for the access points to the axially running pipes.

[0010] According to the invention, the front and rear end sections and the outer casing encapsulate the rotor and the stator in the type of ignition protection Ex d. This makes the electric machine usable even in potentially explosive atmospheres.

[0011] The axially extending tubes have an inner diameter and an outer diameter. Preferably, the axially extending tubes have a radial distance from the stator that is at least as large as the inner diameter, and in particular at least as large as the outer diameter. This easily creates a space in which a seal can be arranged to seal the two end elements against the end faces.

[0012] It is possible that the axially extending pipes are designed as double-walled pipes, each comprising an inner pipe carrying the liquid cooling medium and an outer pipe surrounding the inner pipe, around which the air flowing from the inner to the outer area flows. While this design is relatively complex, it offers the advantage that a simple leak in one of the inner pipes cannot lead to an accumulation of liquid in the inner area.

[0013] Alternatively, it is possible that the axially running pipes are designed as single-walled pipes, which carry the liquid cooling medium inside and are surrounded on the outside by the air flowing from the inside to the outside.

[0014] In both cases, it is advantageous to have a liquid detection device installed indoors and / or outdoors. This allows the risk of an electrical short circuit caused by the liquid cooling medium to be detected in time, providing a warning and potentially even automatically shutting down the electrical machine.

[0015] Preferably, the axially extending tubes are arranged at an angle of more than 180° around the axis of rotation. This allows for efficient cooling despite a relatively compact design. In other cases, however, this angle can be reduced.

[0016] Preferably, the stator is surrounded by an inner shell without a gap, and the inner shell has a radial distance from the outer shell.

[0017] The properties, features, and advantages of this invention described above, as well as the manner in which they are achieved, will become clearer and more readily understandable in connection with the following description of the exemplary embodiments, which are explained in more detail in conjunction with the drawings. These drawings show, in schematic representation: FIG 1 a longitudinal section through an electric machine, FIG 2 a section along a line II-II in FIG 1 , FIG 3 a detail of FIG 1 , FIG 4 a single tube, FIG 5 a single tube, FIG 6 a section of an outer jacket and FIG 7 a section of an inner jacket.

[0018] According to FIG 1 An electric machine has a rotor 1 and a stator 2. The rotor 1 is arranged on a rotor shaft 3, which is mounted so that it can rotate. The rotor shaft 3, and with it the rotor 1, can therefore rotate about a rotational axis 4 of the electric machine.

[0019] In all subsequent uses of the terms "axial," "radial," and "tangential," they always refer to the axis of rotation 4. "Axial" is a direction parallel to the axis of rotation 4. "Radial" is a direction orthogonal to the axis of rotation 4, pointing directly toward or away from it. "Tangential" is a direction that is orthogonal to both the axial and radial directions. Therefore, "tangential" is a direction that, at a constant axial position and a constant radial distance from the axis of rotation 4, is circular around the axis of rotation 4.

[0020] In the context of the present invention, the stator 2 is arranged radially outside, and the rotor 1 radially inside. Furthermore, the stator 2 is arranged as shown in FIG 1 The stator 2 is surrounded by an inner shell 5 without any gap. However, this is not strictly necessary. Alternatively, the stator 2 could also be surrounded by several rings, with at least one ring arranged at each of the two axial ends of the stator 2. The stator 2 is, however, surrounded by an outer shell 6. The outer shell 6 has a radial distance a1 from the stator 2 and, if applicable, from the inner shell 5.

[0021] The outer shell 6 typically has a cylindrical shape. The same generally applies to the inner shell 5, if present. The radial distance a1 is often constant in the tangential direction. However, deviations from a cylindrical shape are possible for both the outer shell 6 and, if applicable, the inner shell 5. The radial distance a1 can therefore also vary.

[0022] The outer shell 6 extends axially from a front end section 7 to a rear end section 8. The two end sections 7, 8 are generally formed in one piece or each consists of several parts bonded together. The two end sections 7, 8 and the stator 2, or optionally the inner shell 5, define an inner region 9. The inner region 9 contains the rotor 1. Furthermore, the two end sections 7, 8, the stator 2, and the outer shell 6 define an outer region 10 that radially surrounds the inner region 9. Preferably, the two end sections 7, 8, and the outer shell 6 also encapsulate the rotor 1 and the stator 2 with explosion protection type Ex d. The term "explosion protection type Ex d" has a fixed meaning for those skilled in the art. Corresponding implementations of the encapsulation are also familiar to those skilled in the art.

[0023] The inner chamber 9 and the outer chamber 10 are interconnected via openings 11, allowing air 12 to flow from the inner chamber 9 into the outer chamber 10 and back again. If the inner jacket 5 is present, the openings 11 can be located in the inner jacket 5. The air 12 flowing from the inner chamber 9 to the outer chamber 10 and back forms an internal cooling circuit for the electric machine.

[0024] The internal cooling circuit is usually – although exceptions are possible – single-flow or dual-flow. In the case of a single-flow internal cooling circuit, the following applies as shown in the diagram. FIG 1 Each end piece 7, 8 has a recess 11 near it. Air 12 flows from the inner area 9 to the outer area 10 through one of these recesses 11, and from the outer area 10 to the inner area 9 through the other. In a dual-flow internal cooling circuit (not shown, but equally feasible), an additional recess 11 is located approximately midway between the end pieces 7, 8. In this case, air 12 flows from the outer area 10 to the inner area 9 through the two recesses 11 near the end pieces 7, 8, and from the inner area 9 to the outer area 10 through the recess located between them. These and potentially other configurations of the internal cooling circuit are generally known to those skilled in the art and therefore require no further explanation.

[0025] Pipes 13 are attached to the two end pieces 7 and 8. The pipes 13 run axially. Each pipe 13 extends from the front end piece 7, across the outer surface 10, to the rear end piece 8. The pipes 13 are generally attached to the end pieces 7 and 8 in such a way that they cannot be removed from the end pieces 7 and 8 without damage. For example, they may be welded to the end pieces 7 and 8.

[0026] The pipes 13 are as shown in the illustration. FIG 2 They are typically arranged in the tangential direction over an angle of more than 180° around the axis of rotation 4. Specifically, in FIG 2 arrangement shown and also the one in FIG 2 The number of pipes shown (13) is only an example. FIG 2 Only some of the pipes 13 are marked with their reference symbol, in order to FIG 2 not to be transported unnecessarily. Often, the pipes 13, viewed tangentially, are even arranged over an angle of more than 270° around the axis of rotation 4, sometimes even as shown in FIG 2 essentially all around. As a rule, the pipes 13 are arranged in essentially equal proportions on both sides of a vertical plane E containing the axis of rotation 4.

[0027] A front end element 14 is placed on the front end piece 7 on its side facing away from the outer shell 6 - i.e. in the axial direction. FIG 3 This is shown in detail. The design of the connection between the front end piece 7 and the front end piece 14 is such that a liquid-tight seal is created. The front end piece 7 and the front end piece 14 thus enclose a front cavity 15.

[0028] For a liquid-tight seal, sealing elements 16 can be arranged between the front end piece 7 and the front end piece 14. The sealing elements 16 can, for example, be designed as O-rings. Optionally, the front end piece 14 and / or the front end piece 7 can have recesses 17 for the sealing elements 16. However, other types of sealing are also possible. For example, the front end piece 14 can be welded to the front end piece 7.

[0029] Similarly, a rear end element 18 is attached to the rear end section 8 on its side facing away from the outer shell 6, so that the rear end section 8 and the rear end element 18 enclose a rear cavity 19. The design of the connection between the rear end section 8 and the rear end element 18 is generally analogous to the design of the connection between the front end section 7 and the front end element 14. In particular, sealing elements 20, optionally including recesses 21 for the sealing elements 20, can also be present here, and welding is also possible here.

[0030] The pipes 13 lead into the as shown in the diagram. FIG 1 and 3in the two cavities 15, 19. Furthermore, the front cavity 15 has a connection 22 through which a liquid cooling medium 23 can be supplied to the front cavity 15. The liquid cooling medium 23 is usually water. In individual cases, however, it can also be another medium, for example, oil. The connection 22 can be positioned as required. In the illustration according to the FIG 1 and 3 A radial feed to the front cavity 15 is provided. However, an axial feed to the front cavity 15 is also possible.

[0031] The pipes 13 show, according to the illustration in FIG 3 The tubes 13 have an inner diameter d1 and an outer diameter d2. They also have a radial distance a2 from the stator 2. If the inner shell 5 is present, the distance a2 is preferably determined from the inner shell 5. Preferably, the respective radial distance a2 is at least as large as the inner diameter d1. Even better is if the respective radial distance a2 is at least as large as the outer diameter d2. This ensures, in particular, that the two end faces 7, 8 have a sufficiently large radial extension in their radially inner region towards the stator 2, in which no tubes 13 are arranged, so that the corresponding end element 14, 18 – optionally including sealing element 16, 20 – can be arranged there.

[0032] FIG 4 shows a possible configuration of one of the pipes 13. For the others, in FIG 4 Analogous provisions apply to the pipes 13 not shown.

[0033] According to the representation in FIG 4 The pipe 13 is designed as a double-walled pipe 13. It therefore has an inner pipe 25 and an outer pipe 26 surrounding the inner pipe 25. The inner pipe 25 carries the liquid cooling medium 23. The outer pipe 26 is surrounded by air 12 at its outer surface 10, i.e., air 12 of the inner cooling circuit. The distance between the inner pipe 25 and the outer pipe 26 should be as small as possible. Optionally, a relatively thermally conductive medium 27, such as an oil, a gel, or an adhesive, can be placed between the inner pipe 25 and the outer pipe 26.

[0034] FIG 5 This also shows a possible configuration of one of the pipes 13. This configuration is an alternative to the configuration of FIG 4 For the others, in FIG 5 The following analogous provisions apply to the pipes 13 not shown:

[0035] According to the representation in FIG 5 The pipe 13 is designed as a single-walled pipe 13. Inside it carries the liquid cooling medium 23 and on the outside is surrounded by the air 12 flowing in the outer area 10, i.e., the air 12 of the inner cooling circuit.

[0036] In the case of the design according to FIG 5 is preferably in accordance with the representation in FIG 6 A detector device 28 is arranged in the outer area 10. The detector device 28 serves to detect whether liquid, i.e., the liquid cooling medium 23, is present in the outer area 10. Such detector devices 28 are generally known to those skilled in the art. For example, a small depression 29 can be arranged in a relatively deep area of ​​the outer shell 6, in which the liquid cooling medium 23 can collect if it escapes from one of the pipes 13 and thus enters the outer area 10. Conductor ends 30 can be arranged in the depression 29 as a detector device 28, which are conductively connected to each other by such an accumulation of the liquid cooling medium 23.

[0037] An analogous design can be implemented according to FIG 7 for the interior area 9. The design according to FIG 7 can be used as needed, either as an alternative or in addition to the design according to FIG 6 to be realized.

[0038] The design according to the FIG 6 and / or 7 can in principle also be combined with the design of the pipes 13 according to FIG 4 can be combined. However, this is not necessary if the pipes 13 are designed as double-walled pipes.

[0039] According to the present invention, the liquid cooling medium 23 is both supplied to and discharged from the front cavity 15. This is described below in conjunction with FIG 2 explained in more detail.

[0040] According to FIG 2 The front end element 14 has at least one partition 31. The partition 31 can, for example, be arranged as shown in FIG 2The pipes run vertically. By means of the partition 31, the front cavity 15 is divided into at least two sub-sections 32 and 33. One part of the pipes 13 opens into sub-section 32, another part of the pipes 13 into sub-section 33. Sub-section 32 has the connection 22, through which the liquid cooling medium 23 is supplied to the front cavity 15 – more precisely: to sub-section 32 of the front cavity 15. The other sub-section 33 has a connection 34, through which the liquid cooling medium 23 is discharged from the front cavity 15 – more precisely: from the other sub-section 33 of the front cavity 15. The liquid cooling medium 23 therefore initially flows via the connection 22 into the sub-area 32, then flows via the pipes 13 opening into the rear cavity 19, then flows back into the sub-area 33 via the pipes 13 opening into the sub-area 33 and is discharged from there via the connection 34 out of the front cavity 15.

[0041] The two sections are thus separated from each other in a liquid-tight manner by means of the partition 31. Furthermore, the front cavity 15 is liquid-tight, with the exception of the connections 22 and 24 for supplying and discharging the liquid cooling medium 23 and the access points to the axially extending pipes 13. Likewise, the rear cavity 19 is liquid-tight, with the exception of the access points to the axially extending pipes 13.

[0042] In summary, the present invention relates to the following situation: An electric machine has a rotor 1 and a stator 2, wherein the rotor 2 is rotatable about an axis of rotation 4. The rotor 1 is radially outside the stator 2, and the stator 2 is at a radial distance a1 from an outer shell 6. The outer shell 6 extends axially from a front end face 7 to a rear end face 8, such that the end faces 7, 8, and stator 2 define an inner region 9 containing the rotor 1, and the end faces 7, 8, stator 2, and the outer shell 6 define an outer region 10 radially surrounding the inner region 9. The inner region 9 and the outer region 10 are interconnected via recesses 11, allowing air 12 to flow from the inner region 9 into the outer region 10 and back again.Axially extending tubes 13 are attached to the end faces 7, 8, extending between the end faces 7, 8 in the outer area 10. Liquid-tight end caps 14, 18 are fitted to each end face 7, 8 on their sides facing away from the outer shell 6, so that the end faces 7, 8 and the end caps 14, 18 each enclose a cavity 15, 19. The front cavity 15 is divided into at least two sub-areas 32, 33 by means of a partition 31. A portion of the tubes 13 opens into each of the sub-areas 32, 33. A connection 22, 34 for supplying and discharging the liquid cooling medium 23 is arranged in each of the sub-areas 32, 33.

[0043] The present invention offers many advantages. In particular, the cooling of the electric machine can be significantly improved. This allows the electric machine to be operated at a higher power output with the same size and the same or even reduced weight. In tests, power increases of approximately 25% have proven readily achievable. Furthermore, the noise emission of the electric machine can be reduced. Although the invention has been illustrated and described in detail by the preferred embodiment, the invention is not limited by the disclosed examples, and other variations can be derived by those skilled in the art without departing from the scope of protection of the invention as defined by the claims.

Claims

1. An encapsulated electric machine having an air internal cooling circuit and an external liquid cooling circuit, wherein the electric machine includes a rotor (1) and a stator (2), - wherein the rotor (2) is rotatable about an axis of rotation (4) of the electric machine, - wherein, when viewed around the axis of rotation (4), the rotor (1) is surrounded by the stator (2), and the stator (2) is surrounded by an outer sheath (6) at a radial distance (a1), - wherein the radial distance (a1) varies, - wherein the outer sheath (6) extends, as viewed in the direction of the axis of rotation (4), in each case from a front end part (7) to a rear end part (8), such that the front and the rear end part (7, 8) and the stator (2) delimit an interior region (9) containing the rotor (1), and the front and the rear end part (7, 8), the stator (2), and the outer sheath (6) delimit an exterior region (10) radially surrounding the interior region (9), - wherein the interior region (9) and the exterior region (10) are communicatively connected to each other via recesses (11) such that air (12) can flow from the interior region (9) into the exterior region (10) and from there back to the interior region (9), - wherein axially extending tubes (13) are respectively fastened in the front and the rear end part (7, 8), such that the axially extending tubes (13) each extend from the front end part (7) via the exterior region (10) to the rear end part (8), - wherein the axially extending tubes are arranged distributed around the axis of rotation over an angle of more than 180°, as viewed around the axis of rotation, - wherein, on the respective side of the front and the rear end part (7, 8) facing away from the outer sheath (6), a front and a rear closing element (14, 18) are mounted in a fluid-tight manner, such that the front end part (7) and the front closing element (14) enclose a front cavity and the rear end part (8) and the closing element (18) surround a rear cavity (15, 19), - wherein the axially extending tubes (13) open in the front and rear cavity (15, 19), and - wherein at least the front cavity (15) comprises a port (22) for supplying a liquid cooling medium (23) characterized in that the front and the rear end part (7, 8) and the outer sheath (6) encapsulate the rotor (1) and the stator (2) in the Ex d type of protection.

2. An electrical machine according to claim 1, characterized in that the rear cavity (18) comprises a port (24) for discharging the liquid cooling medium (23).

3. An electrical machine according to claim 1, characterized in that the front cavity (15) is divided into at least two sub-areas (32, 33) such that a part of the axially extending tubes (13) opens into one of the sub-areas (32, 33) and another part of the axially extending tubes (13) opens into another of the sub-areas (32, 33), that the port (22) for supplying the liquid cooling medium (23) is arranged in the one sub-area (32), and that a port (34) for discharging the liquid cooling medium (23) from the front cavity (15) is arranged in the other sub-area (33).

4. An electrical machine according to any preceding claim, characterized in that the axially extending tubes (13) have an inner diameter (d1) and an outer diameter (d2) and in that the axially extending tubes (13) have, from the stator (2), a respective radial distance (a2) that is at least as large as the inner diameter (d1).

5. An electrical machine according to claim 4, characterized in that the respective distance (a2) of the axially extending tubes (13) from the stator (2) is at least as large as the outer diameter (d2).

6. The electrical machine according to any one of claims 1 to 5, characterized in that the axially extending tubes (13) are embodied as double-walled tubes comprising an inner tube (25) guiding the liquid cooling medium (23) and an outer tube (26) surrounding the inner tube (25) and being flowed around by the air (12) flowing in the exterior region (10).

7. The electrical machine according to any one of claims 1 to 5, characterized in that the axially extending tubes (13) are embodied as single-walled tubes that guide the liquid cooling medium (23) on the inside and are flowed around on the outside by the air (12) flowing in the exterior region (10).

8. The electrical machine according to claim 6 or 7, characterized in that a detector device (28) for sensing liquid is arranged in the interior area (9) and / or in the exterior area (10).

9. The electrical machine according to any of the above claims, characterized in that the axially extending tubes (13) are arranged distributed around the axis of rotation (4), as viewed around the axis of rotation (4), over an angle of more than 180°.

10. The electrical machine according to any one of the above claims, characterized in that the stator (2) is surrounded by an inner sheath (5) without any gap and that the inner sheath (5) has a radial distance from the outer sheath (6).