Sealing Systems for Permanent Magnet Motors / Generators

Abstract

The electric machine (100) comprises a rotating magnetic assembly (10) preferably comprising a permanent magnet, a stationary magnetic assembly (20) preferably comprising an electromagnet, a rotating hub (30) having a cylindrical shape and a tubular recess (31) for receiving the rotating magnetic assembly (10), and a sleeve (40) positioned to surround the tubular recess (31) and mechanically coupled to the rotating hub (30). The sleeve (40) has a first end region (41) and a second end region (42) sealed to the rotating hub (30) to fluidically isolate the tubular recess (31). The rotating hub (30) comprises at least one internal channel (250, 350, 450) fluidically coupled to the tubular recess (31).

Description

[Technical field]

[0001] The subject matter disclosed herein relates to a sealing system for a permanent magnet motor / generator. More particularly, the subject matter disclosed herein relates to a sealing system for a permanent magnet motor / generator that allows for the use of, for example, hydrogen as a cooling fluid. [Background technology]

[0002] Typically, rotating electric machines are energy converters that can convert electrical energy into mechanical energy (i.e., when the electric machine operates as a motor) or mechanical energy into electrical energy (i.e., when the electric machine operates as a generator). Various types of electric machines can include permanent magnets. For example, a conventional brushless motor includes a permanent magnet attached to a rotor of the electric machine, the permanent magnet having an air gap distance from a stator of the electric machine, and establishes a magnetic field.

[0003] It should be noted that permanent magnets maintain their magnetism for several years if maintained and used in optimal operating conditions, which may include not exposing the magnets to high temperatures (especially above their maximum operating temperature) and protecting them from corrosion. For this reason, electric machines must be properly cooled and protected from contact with aggressive fluids that may degrade materials such as permanent magnets. However, when an electric machine is coupled to a turbomachine, for example a compressor or expander that processes a fluid (i.e. compresses or expands the fluid), the electric machine must be fluidically isolated from the process fluid, which may be dangerous for the electric machine materials. This is typically done by equipping the electric machine with dry gas seals that allow isolating the electric machine from the processed gases, for example the processed gases of a compressor and / or expander coupled to the electric machine, and / or by cooling the electric machine and its parts, in particular its rotating magnetic assembly and its stationary magnetic assembly, with a cooling fluid, typically air.

[0004] However, properly equipping an electric machine with suitable components to ensure correct operation and maintenance of its parts contrasts with the desire to have a compact electric machine. Summary of the Invention

[0005] It is desirable to have an electric machine that is properly cooled and in which the rotating and stationary magnetic assemblies are protected from degradation.

[0006] According to one aspect, the subject matter disclosed herein relates to an electric machine including a rotating magnetic assembly, a fixed magnetic assembly, a cylindrical rotating hub having a tubular recess for receiving the rotating magnetic assembly, and a sleeve positioned around the tubular recess to surround the tubular recess. The sleeve has a first end region and a second end region mechanically coupled to the rotating hub and sealed to the rotating hub to fluidically isolate the tubular recess. The rotating hub includes at least one internal channel fluidly coupled to the tubular recess.

[0007] According to another aspect, the subject matter disclosed herein relates to a machine comprising an electric machine having a first shaft comprising a fluidly isolated rotating magnetic assembly, and a compressor and / or an expander having a second shaft, wherein the first shaft and the second shaft are mechanically coupled. [Brief description of the drawings]

[0008] A complete understanding of the disclosed embodiments of the present invention and many of the attendant advantages thereof will be readily obtained as the same become better understood by reference to the following detailed description when considered in connection with the accompanying drawings, in which: [Figure 1] FIG. 1 illustrates a simplified partial cross-sectional view of one embodiment of an electric machine having a sleeve for sealing a rotating magnetic assembly. [Diagram 2]FIG. 2 illustrates a simplified partial cross-sectional view of another embodiment of an electric machine having a sleeve for sealing a rotating magnetic assembly having a rotating hub connected by a tie rod. [Diagram 3] FIG. 3 illustrates a simplified partial cross-sectional view of another embodiment of an electric machine having a sleeve for sealing a rotating magnetic assembly having a different shape. [Figure 4] FIG. 4 illustrates a simplified cross-sectional view of another embodiment of an electric machine with a sleeve for sealing a rotating magnetic assembly having a dual sealing assembly. [Diagram 5] FIG. 5 shows a simplified cross-sectional view of a machine comprising an electric machine according to any of the FIGS. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0009] According to one aspect, the subject matter disclosed herein relates to an electric machine, preferably coupled to a turbomachine, such as a compressor or an expander, and using in particular hydrogen as both a process fluid of the turbomachine and a cooling fluid of the electric machine. The electric machine has a rotor assembly, typically a rotating hub having a recess for housing a permanent magnet of the rotor assembly, typically a tubular recess located on the outer surface of the rotating hub. The electric machine further has a stator assembly, typically comprising an electromagnet, which surrounds the rotor assembly and defines a first passage between itself and the rotor assembly, the first passage adapted to carry a cooling fluid of the electric machine. To protect the permanent magnet of the rotor assembly, the electric machine further comprises a sleeve sealed to the rotating hub so as to fluidically isolate the tubular recess housing the permanent magnet. To stabilize the permanent magnet, the rotating hub comprises at least one internal channel fluidly coupled to the tubular recess, which may advantageously be configured and possibly filled with a suitable filling.

[0010] Next, the embodiments of the present disclosure will be described in detail, and examples thereof will be illustrated in the drawings. The embodiments and drawings are provided as explanations of the present disclosure and should not be construed as limiting the present disclosure. In fact, it will be apparent to those skilled in the art that various modifications and variations can be made to the present disclosure without departing from the scope or spirit of the present disclosure. In the following description, similar reference numbers are used in the illustrations of the embodiment figures to indicate elements that perform the same or similar functions. Moreover, for clarity of illustration, some reference numbers may not be repeated in all figures.

[0011] In Fig. 1, a (partial) simplified cross-sectional view of an embodiment of an electric machine with a sleeve configured to seal a rotating magnetic assembly is shown, the electric machine being generally indicated with the reference number 100. The electric machine 100 comprises a rotating magnetic assembly 10 (only shown very diagrammatically in Fig. 1), a fixed magnetic assembly 20 (only shown very diagrammatically in Fig. 1) and a rotating hub 30 having a cylindrical shape. Advantageously, the rotating hub 30 is part of a shaft of the electric machine 100 that determines an axis X. As will become clear below, the rotating hub 30 is configured to house the rotating magnetic assembly 10 and the fixed magnetic assembly 20 is arranged around the rotating hub 30, more specifically around a part of the rotating hub 30.

[0012] It should be noted that electric machine 100 may be configured as an electric motor or a generator, or as both an electric motor and a generator. For example, electric machine 100 may be started as an electric motor and then switched over to being a generator, particularly once the mechanical torque exceeds the electric torque.

[0013] With non-limiting reference to FIG. 1, the rotating hub 30 has a tubular recess 31, in particular in the form of a groove on the side of the rotating hub 30, for accommodating the rotating magnetic assembly 10. According to a preferred embodiment, the rotating magnetic assembly 10 comprises a permanent magnet. As better explained with non-limiting reference to FIGS. 2 to 4, the rotating hub 30 comprises at least one internal channel (not shown in FIG. 1) fluidically coupled to the tubular recess 31, which may advantageously be configured to fill the tubular recess 31 with a suitable filling, possibly to fill it with a suitable filling, in particular to stabilize the permanent magnet accommodated in the tubular recess 31. As will become clear from the following, the fixed magnetic assembly 20 is arranged to surround the rotating magnetic assembly 10. According to a preferred embodiment, the fixed magnetic assembly 20 comprises an electromagnet.

[0014] 1, the electric machine 100 further comprises a sleeve 40 mechanically coupled to the rotating hub 30 and positioned around the tubular recess 31 to surround, and in particular to completely surround, the tubular recess 31. As shown in FIG. 1, the sleeve 40 has a first end region 41 and a second end region 42 that extend beyond the tubular recess 31 and are sealed to the rotating hub 30 to fluidically isolate the tubular recess 31.

[0015] As already mentioned, the fixed magnetic assembly 20 is disposed to surround the rotating magnetic assembly 10, in particular, the sleeve 40 is surrounded such that the outer surface of the sleeve 40 and the inner surface of the fixed magnetic assembly 20 face each other. It should be noted that the fixed magnetic assembly 20 and the rotating magnetic assembly 10 are radially spaced apart such that there is a radial gap between them. It should be noted that the radial gap between the fixed magnetic assembly 20 and the rotating magnetic assembly 10 may vary from point to point and may vary based on distinct cross sections of the electric machine 100, for example due to the presence or absence of electromagnets. In other words, the shape of the space between the outer surface of the sleeve and the inner surface of the magnetic assembly may be approximately cylindrical, but not exactly cylindrical.

[0016] The electric machine 100 further comprises a cooling system, in particular for circulating a cooling fluid to cool the electric machine 100 (see, for example, the black arrows in FIG. 1 ). The cooling system comprises a first passage 25 defined at least in part between an outer surface of the sleeve 40 and an inner surface of the fixed magnetic assembly 20. According to a first approximation, the first passage 25 can be considered as a cylindrical passage which in cross section determines an approximately circular crown about the X-axis. Such crown may vary along the longitudinal direction.

[0017] Advantageously, the first passage 25 is adapted to pass a cooling fluid, preferably consisting of or including hydrogen. According to different embodiments, the cooling fluid may consist of or include, for example, CO2, preferably in a supercritical state, or helium.

[0018] Advantageously, the sleeve 40 is made of or contains a nickel-chromium based superalloy or carbon fiber, in particular to protect the permanent magnets of the rotating magnetic assembly 10 from the cooling fluid, for example to prevent the penetration of the cooling fluid, in particular hydrogen, within the tubular recess 31.

[0019] 1 shows a first embodiment of an electric machine 100, in which only the first end region 41, or only the second end region 42, or both the first end region 41 and the second end region 42 of the sleeve 40 are welded to the rotor hub 30. According to one possibility, the sleeve 40 can first be heated up to about 300° C., in particular to expand the sleeve 40, and then positioned around the tubular recess 31, for example by sliding the sleeve 40 along the direction of the axis X until it surrounds the tubular recess 31, and then the sleeve 40 is cooled, in particular to contract the sleeve 40. Finally, the sleeve 40 is welded to the rotor hub 30.

[0020] 2-4 show various embodiments of the sealing coupling between the sleeve and the rotating hub, which in particular comprises at least one seal assembly 260 or 360 or 460, preferably two seal assemblies, mechanically coupled to the first end region and / or the second end region of the sleeve, as will be better explained below. For example, it is noted that with reference to FIG. 2, the expression "seal assembly 260" is generally used for any of the seal assemblies 260-1, 260-2, 260-3, and 260-4. Similarly, with reference to FIG. 3, the expression "seal assembly 360" is generally used for any of the seal assemblies 360-1 and 360-2, and with reference to FIG. 4, the expression "seal assembly 460" is generally used for any of the seal assemblies 460-1, 460-2, 460-3, and 460-4. The seal assembly 260 or 360 or 460 may comprise, for example, a C-ring seal, a spring-loaded C-ring seal, a cup seal, or an O-ring seal made, for example, of a metal or a synthetic polymer (specifically polytetrafluoroethylene, also known as "PTFE"). Note that for clarity, the stator assembly is not shown in Figures 2-4.

[0021] A second embodiment 200 of the electric machine is described below with the aid of Fig. 2. It is noted that elements 210, 230, 231, 240, 241 and 242 in Fig. 2 may be identical or similar to elements 10 (rotating magnetic assembly), 30 (rotating hub), 31 (tubular recess), 40 (sleeve), 41 (first end region) and 42 (second end region) in Fig. 1, respectively, and may perform the same or similar functions.

[0022] 2 , the rotating hub 230 of the electric machine 200 is mechanically coupled to a shaft 280, e.g., the shaft of the electric machine 200. For example, the rotating hub 230 may be coupled to the shaft 280 by a tie rod 270 that passes through the rotor hub 230. The tie rod 270 may be used to press a first side of the rotor hub 230 against the shaft 280 and a flange 275 against a second side of the rotor hub 230. In particular, the tie rod 270 is mechanically coupled to the rotor hub 230 by a nut 271 that secures the tie rod 270 to the rotor hub 230.

[0023] 2 includes two seal assemblies 260-1 and 260-2 mechanically coupled to a first end region 241 of the sleeve 240 and two seal assemblies 260-3 and 260-4 mechanically coupled to a second end region 242 of the sleeve 240. In particular, the electric machine 200 includes an inner seal assembly 260-2 and an outer seal assembly 260-1 at the first end region 241 of the sleeve 240, and an inner seal assembly 260-4 and an outer seal assembly 260-3 at the second end region 242 of the sleeve 240. Advantageously, the seal assemblies 260-1 and 260-2 can prevent leakage of the cooling fluid from a possible gap between the shaft 280 and the rotor hub 230, and the seal assemblies 260-3 and 260-4 can prevent leakage of the cooling fluid from a possible gap between the flange 275 and the rotor hub 230.

[0024] Advantageously, the electric machine 200 further comprises at least one internal channel 250 fluidically coupled to the tubular recess 231. According to the embodiment of FIG. 2, the electric machine 200 comprises a first channel 250-1 fluidically coupling a first side of the rotor hub 230 with the tubular recess 231 and preferably a second channel 250-2 fluidically coupling a second side of the rotor hub 230 with the tubular recess 231 (see dashed lines in FIG. 2). In particular, the internal channels 250-1 and 250-2 are configured to fill the tubular recess 231 with an epoxy molding compound or a synthetic oil, possibly to be filled with an epoxy molding compound or a synthetic oil. Advantageously, the epoxy molding compound or the synthetic oil may fill possible gaps between the rotor assembly 210 and the tubular recess 231. Alternatively, tubular recess 231 and possibly interior channels 250-1 and 250-2 may be filled with aluminum oxide (also known as "alumina") or a compound containing aluminum oxide, such as nickel aluminate.

[0025] A third embodiment 300 of the electric machine is described below with reference to Fig. 3. It is noted that elements 310, 330, 331, 340, 341 and 342 in Fig. 3 are the same as or similar to elements 10 (rotating magnetic assembly), 30 (rotating hub), 31 (tubular recess), 40 (sleeve), 41 (first end region) and 42 (second end region) in Fig. 1, respectively, and may perform the same or similar functions.

[0026] According to the embodiment of Fig. 3, the rotating hub 330 of the electric machine 300 has different cross sections, in particular a first larger cross section and a second smaller cross section, and defines a wall at the transition between the first and second cross sections. Advantageously, the sleeve 340 is configured to surround both the tubular recess 331 and the wall. In other words, the second end region 342 of the sleeve 340 is configured to at least partially cover the wall of the rotor hub 330.

[0027] The electric machine 300 of FIG. 3 comprises a first seal assembly 360-1 mechanically coupled to a first end region 341 of the sleeve 340 and a second seal assembly 360-2 mechanically coupled to a second end region 342 of the sleeve 340. According to one possibility, the sleeve 340 may first be heated to about 300° C., in particular to expand it, and then positioned around the tubular recess 331, for example by sliding it along the direction of the axis X, until the sleeve 340 surrounds the tubular recess 331 and the second end region 342 abuts the wall of the rotor hub 330. A weight may then be placed on the sleeve 340, such that at least the second seal assembly 360-2 is compressed by the weight. Finally, the sleeve 340 may be cooled, in particular to contract it, and the weight may be removed, such that at least the second seal assembly 360-2 is kept compressed by the sleeve 340.

[0028] Advantageously, the electric machine 300 further comprises at least one internal channel 350 fluidly coupled to the tubular recess 231 and configured to fill the tubular recess 331 with an epoxy molding compound or a synthetic oil, as the case may be (see dashed lines in FIG. 3 ). Advantageously, the epoxy molding compound or the synthetic oil may fill any possible gap between the rotor assembly 310 and the tubular recess 331. Alternatively, the tubular recess 331 and possibly also the internal channel 350 may be filled with aluminum oxide (also known as “alumina”) or a compound containing aluminum oxide, for example nickel aluminate.

[0029] A fourth embodiment 400 of the electric machine is described below with the aid of Fig. 4. It is noted that elements 410, 430, 431, 440, 441 and 442 in Fig. 4 may be identical or similar to elements 10 (rotating magnetic assembly), 30 (rotating hub), 31 (tubular recess), 40 (sleeve), 41 (first end region) and 42 (second end region) in Fig. 1, respectively, and may perform the same or similar functions.

[0030] 4, the electric machine 400 comprises two seal assemblies 460-1 and 460-2 mechanically coupled to a first end region 441 of the sleeve 440 and two seal assemblies 460-3 and 460-4 mechanically coupled to a second end region 442 of the sleeve 440. In particular, both seal assemblies 460-1 and 460-2 and seal assemblies 460-3 and 460-4 are adjacent to one another along the axial direction.

[0031] Advantageously, the electric machine 400 further comprises at least one internal channel 450 fluidly coupled to the tubular recess 231 and configured to fill the tubular recess 431 with an epoxy molding compound or a synthetic oil, possibly with an epoxy molding compound or a synthetic oil (see dashed lines in FIG. 4). Advantageously, the epoxy molding compound or the synthetic oil may fill any possible gap between the rotor assembly 410 and the tubular recess 431. Alternatively, the tubular recess 431 and possibly also the internal channel 450 may be filled with aluminum oxide (also known as "alumina") or a compound containing aluminum oxide, for example nickel aluminate.

[0032] According to another possibility not shown, the above-mentioned embodiments, in particular the embodiment of the sealing of the sleeve against the rotating hub, can be combined with each other, for example the sleeve can have a first end region welded to the rotating hub and a second end region provided with a seal assembly mechanically coupled to the rotating hub.

[0033] According to another aspect, the subject matter disclosed herein is a machine comprising: an electric machine comprising a rotating magnetic assembly, a fixed magnetic assembly, a rotating hub having a tubular recess for accommodating the rotating magnetic assembly, and a sleeve having a first end region and a second end region positioned around the tubular recess so as to surround the tubular recess and sealed to the rotating hub so as to fluidically isolate the tubular recess, the rotating hub being fluidly coupled to the tubular recess and advantageously configured to fill the tubular recess with a suitable filling material, the electric machine comprising at least one internal channel which may possibly be filled with a suitable filling material; - a compressor and / or an expander, The present invention relates to a machine in which the electric machine has a first shaft and the compressor and / or expander has a second shaft, the first shaft and the second shaft being mechanically coupled.

[0034] With non-limiting reference to FIG. 5, a machine generally designated by reference number 1000 is very diagrammatically shown, comprising an electric machine 100 having a first shaft 130 and at least one mechanical machine 1100 (e.g. compressor or expander) having a second shaft 1150 mechanically coupled to the first shaft 130, for example welded to the first shaft 130. Both shafts may also be realized in a single piece. In the embodiment of FIG. 5, only one mechanical machine is arranged on one side of the electric machine. According to a first alternative, there may be, for example, at least one first electric machine arranged on the first side of the electric machine and at least one second electric machine arranged on the second side of the electric machine. According to a second alternative, there may be, for example, two or more mechanical machines arranged on one or both sides of the electric machine.

[0035] Advantageously, the machine 1000 further comprises a cooling system configured to circulate a cooling fluid for cooling at least the electric machine 100. In particular, the cooling system comprises a first passage 25 for flowing the cooling fluid, at least partially defined between an outer surface of the sleeve 40 and an inner surface of the stationary magnetic assembly 20 of the electric machine 100. According to a preferred embodiment, the cooling fluid is a process fluid processed by the compressor and / or the expander 1100. For example, the cooling fluid consists of or comprises hydrogen.

[0036] 5, the machine 1000 may further comprise at least a magnetic bearing 1200, advantageously two magnetic bearings 1200-1 and 1200-2, the first magnetic bearing 1200-1 being arranged at a first end of the electric machine 100, in particular between the first end of the electric machine 100 and the compressor and / or the expander 1100, and the second magnetic bearing 1200-2 being arranged at a second end of the electric machine 100. In particular, the cooling circuit comprises a second passage 1225 for flowing a cooling fluid, at least partially defined between an outer surface of the first shaft 130 and / or the second shaft 1150 and an inner surface of the magnetic bearings 1200-1 and 1200-2. According to a preferred embodiment, the second passages 1225-1 and 1225-2 are fluidly coupled to the first passage 25. In other words, the cooling fluid flowing through the first passage 25 is the same as the cooling fluid flowing through the second passage 1225. For example, the cooling fluid may first flow into the second passage 1225-2 to cool the magnetic bearing 1200-2, then flow into the first passage 25 to cool the electric machine 100, and finally flow into the second passage 1225-1 to cool the magnetic bearing 1200-1.

Claims

1. An electric machine (100, 200, 300, 400), a rotating magnetic assembly (10), - a fixed magnetic assembly (20); a rotating hub (30) having a cylindrical shape and a tubular recess (31) for accommodating said rotating magnetic assembly (10); a sleeve (40) positioned around said tubular recess (31) so as to surround said tubular recess (31) and mechanically coupled to said rotating hub (30); Equipped with the sleeve (40) has a first end region (41) and a second end region (42), the first end region (41) and the second end region (42) being sealed to the rotating hub (30) so as to fluidly isolate the tubular recess (31); The rotating hub (30) includes at least one internal channel (250, 350, 450); The internal channel (250, 350, 450) is fluidly coupled to the tubular recess (31).

2. Further comprising a cooling system; The fixed magnetic assembly (20) surrounds the sleeve (40); The cooling system comprises a first passageway (25) for flowing a cooling fluid; The electric machine (100, 200, 300, 400) of claim 1, wherein the first passageway (25) is defined at least partially between an exterior surface of the sleeve (40) and an interior surface of the fixed magnetic assembly (20).

3. The electric machine (100, 200, 300, 400) of claim 2 , wherein the cooling fluid consists of or includes hydrogen.

4. The electric machine (100) of any of the preceding claims, wherein the sleeve (40) is made of or includes a nickel-chromium based superalloy or carbon fiber.

5. 2. The electric machine (100) of claim 1, wherein the first end region (41) and / or the second end region (42) of the sleeve (40) are welded to the rotating hub (30).

6. at least one seal assembly (260, 360, 460); The electric machine (200, 300, 400) of claim 1, wherein the seal assembly (260, 360, 460) is mechanically coupled to the first end region (241, 341, 441) or the second end region (242, 342, 442) of the sleeve (240, 340, 440).

7. Further comprising at least a first seal assembly (260-1, 260-2, 360-1, 460-1, 460-2) and a second seal assembly (260-3, 260-4, 360-2, 460-3, 460-4); the first seal assembly (260-1, 260-2, 360-1, 460-1, 460-2) is mechanically coupled to the first end region (241, 341, 441); The electric machine (200, 300, 400) of any of the preceding claims, wherein the second seal assembly (260-3, 260-4, 360-2, 460-3, 460-4) is mechanically coupled to the second end region (242, 342, 442).

8. 2. The electric machine (200, 300, 400) of claim 1, wherein the internal channel (250, 350, 450) is configured to fill the tubular recess (231, 331, 431) with an epoxy molding compound or a synthetic oil, and in some cases is configured to be filled with an epoxy molding compound or a synthetic oil.

9. The electric machine (100) of claim 1, wherein the rotating hub (30) is part of a shaft of the electric machine (100).

10. The electric machine (100) of claim 1 configured as an electric motor and / or generator.

11. A machine (1000), - an electric machine (100, 200, 300, 400) according to claim 1, having a first shaft (130); a compressor and / or expander (1100) having a second shaft (1150), Equipped with A machine (1000), wherein the first shaft (130) is mechanically coupled to the second shaft (1150).

12. Further comprising a cooling system; the stationary magnetic assembly surrounds the sleeve; The cooling system comprises a first passageway (25) for flowing a cooling fluid; the first passageway (25) being at least partially defined between an outer surface of the sleeve and an inner surface of the fixed magnetic assembly; The machine (1000) of claim 11, wherein the cooling fluid is a process fluid processed by the compressor and / or expander (1100).

13. At least one magnetic bearing (1200), the magnetic bearing (1200) surrounds the first shaft (130) or the second shaft (1150); the cooling system includes a second passageway (1225) for flowing a cooling fluid; the second passage (1125) is at least partially defined between an outer surface of the first shaft (130) or the second shaft (1150) and an inner surface of the magnetic bearing (1200); The machine (1000) of claim 12, wherein the second passage (1225) is fluidly coupled to the first passage (25).

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