Apparatus and method for cooling

Abstract

To provide an apparatus and a method for cooling an electric motor.SOLUTION: To obtain simple and sufficient cooling, an electric motor is provided with a dual cooling system including: a cooling space (11) provided to the stator (2) for receiving and passing on a cooling fluid which cools the stator; and an inlet (12) and an outlet (13) provided to the electric motor for receiving and passing on a cooling gas flow which cools at least a rotor (4) before exiting the electric motor.SELECTED DRAWING: Figure 3

Description

[Technical field]

[0001]

[0001] The present invention relates to a solution for cooling electric motors. In the following, the invention is explained by reference to an electric motor of a cycloidal propulsion unit as an example, but the cooling method can also be used for other electric motors. [Background technology]

[0002]

[0002] A problem with electric motors, such as those of cycloidal propulsion units, is to provide sufficient cooling for the various parts of the electric motor. Sufficient cooling is essential since the load on the electric motor can be increased if the temperature rise can be avoided. Therefore, if the cooling is efficient, more power can be available from the electric motor without the need to increase the motor diameter or length. Summary of the Invention

[0003]

[0003] The object of the present invention is to provide a solution which ensures sufficient cooling for an electric motor. This object is achieved by an apparatus according to independent claim 1 and by a method according to independent claim 14.

[0004]

[0004] Efficient dual cooling for an electric motor can be obtained by circulating a cooling fluid through the stator and cooling other components of the electric motor with a cooling gas flow that enters the electric motor at an inlet, flows along the rotor and then exits the electric motor via an outlet. Such a solution ensures that the cooling is efficient enough to ensure that a significant amount of power is available from the electric motor without the need to increase the size of the electric motor.

[0005]

[0005] Preferred embodiments of the invention are disclosed in the dependent claims.

[0006]

[0006] In the following, the device and method will be described in more detail, by way of example, with reference to the accompanying drawings, in which: [Brief description of the drawings]

[0007] [Figure 1]

[0007] An example of an electric motor installed in a cycloidal propulsion unit is shown. [Diagram 2] 1 illustrates an electric motor installed in a cycloidal propulsion unit. [Diagram 3] 1 illustrates an electric motor installed in a cycloidal propulsion unit. [Figure 4]

[0008] 2 illustrates a second embodiment of an electric motor. [Diagram 5]

[0009] 3 illustrates a third embodiment of an electric motor. [Figure 6]

[0010] 4 illustrates a fourth embodiment of the electric motor. [Figure 7] 4 illustrates a fourth embodiment of the electric motor. [Figure 8]

[0011] 1 illustrates a fifth embodiment of an electric motor. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0008]

[0012] 1 to 3 illustrate an electric motor installed in a cycloidal propulsion unit, seen from the side in FIG. 1, from above in FIG. 2 and in cross section with the addition of a cooling device in FIG. 3.

[0009]

[0013] The electric motor comprises a stator 2, which is fixedly mounted, in this case in the hull 3 of a ship. A rotor 4 is rotatably arranged in the stator 2. The rotor 4 extends downwards as a rotating casing 5, which rotates together with the rotor 4 about a rotation axis 6 during operation. When the electric motor is mounted in a cycloidal propulsion unit, the rotation axis is in fact oriented vertically.

[0010]

[0014] The lower part of the hollow rotating casing 5 is provided with blades 7, which are located underwater outside the hull 3 and rotate together with the rotating casing around a rotation axis 6. Each blade is further provided with a drive mechanism 8 which rotates the blade 7 separately relative to the rotating casing 5 around a rotation axis 9. Due to the drive mechanism 8 specific to the blade 7, each blade can be controlled separately to rotate in an optimal way. This makes it possible to drive and operate the vessel as required using the cycloidal propulsion unit. The illustrated electric motor can therefore be the main motor of the vessel. The drive mechanism can be implemented using suitable mechanical devices such as, for example, gears and shafts. However, in the following description, it is assumed by way of example that the drive mechanism 8 includes an electric motor driven by a motor drive 10, such as a frequency converter. There is therefore one electric motor for each blade 7. The motor drive 10 can be installed, for example, in the rotating casing 5.

[0011]

[0015] A challenge for an electric motor 1 of the illustrated type is cooling. In the illustrated example, a hybrid cooling solution is used to cool the electric motor 1. This hybrid cooling solution comprises cooling spaces 11 provided in the stator 2 for receiving and passing a cooling fluid which cools the stator. Furthermore, the electric motor 1 is provided with an inlet 12 and an outlet 13 for receiving and passing a cooling gas flow within the stator casing of the electric motor for cooling at least the rotor 4. For simplicity, the inlets, outlets, fans, heat exchangers and cooling spaces are not illustrated in Figures 1 and 2.

[0012]

[0016] The cooling space 11, in which a cooling fluid such as water circulates, may for example be implemented as a cooling jacket. In this case, the cooling space 11 may be implemented as a relatively high-volume annular container surrounding at least a part of the stator 2. Alternatively, depending on the implementation, the cooling space may be implemented as one or more tubes partially surrounding the stator. The cooling space may be implemented as a separate part surrounding and contacting the outer surface of the stator, or alternatively as an integrated part in the outer wall of the stator casing. If integrated in the outer wall, the wall of the stator is at least partially hollow.

[0013]

[0017] In figure 3 it is assumed by way of example that a heat exchanger 14 is arranged for cooling a gas flow, such as an air flow, entering the electric motor 1 via the inlet 12. Preferably, this heat exchanger is at least partially embedded in the illustrated electric motor, which ensures a space-saving, compact design. However, a heat exchanger is not necessary in all embodiments. In FIG. 3, the heat exchanger is connected to a fluid circuit in which a cold fluid is used to cool the gas entering the electric motor 1. This gas flow circulates in the electric motor 1, where it comes into contact with at least the rotor 4, before leaving the electric motor via the outlet 13. In the illustrated example, two outlets are provided as an example, but in some implementations, one outlet may be sufficient. In FIG. 3, it is also illustrated as an example that both outlets 13 are provided with a fan 15, such as a centrifugal fan, but only one fan may be sufficient. In some implementations, a fan may not be necessary at all, if the fluid flow can be generated elsewhere, such as by a building or ship ventilation system that can generate the gas flow required for cooling. If a fan is included, this fan is also preferably at least partially embedded in the illustrated electric motor, in order to provide a compact design.

[0014]

[0018] In figure 3 a closed loop for circulating the gas flow from the outlet 13 to the inlet 12 is implemented by a duct 21 which feeds the heated air flow from the outlet 13 via the heat exchanger 14 back into the electric motor 1. In addition to cooling the rotor 4, the gas flow may also cool the slip ring unit 16, the magnets 17 of the rotor and the windings 18 of the stator 2. The main bearings 29 which rotatably support the rotor and the rotating casing 5 are further cooled to some extent by the gas flow, but may further be provided with a lubricating oil feed device which also cools the main bearings.

[0015]

[0019] Efficient cooling of the magnets and windings is obtained by directing the gas flow through the rotor 4 through at least one opening 19 in FIG. 3, which is located between the magnets 17 and the rotor shaft 6. Furthermore, the gas flow is directed through an annular gap 20 formed along the periphery of the rotor 4, which is shown in FIG. 3 between the magnets 17 of the rotor 4 and the windings 18 of the stator 2. To ensure that the gas flow passes through the at least one opening 19 and the annular gap 20, a wall 23 is provided that extends from a position in close proximity to the periphery of the rotor 4 to the top wall of the motor. This wall 23 prevents the gas flow from passing directly from the inlet to the outlet without first passing through the rotor 4 and the annular gap 20.

[0016]

[0020] 1-3 or other embodiments, magnets are not required in the rotor if another type of electric motor is utilized, such as an induction motor having a wound or squirrel cage induction rotor, and in this case it is advantageous to direct the gas flow through an annular gap 20 formed around the periphery of the rotor 4, since in this case the gas flow cools the rotor windings or squirrel cage.

[0017]

[0021] When the electric motor 1 is used in a cycloidal propulsion unit having a rotating casing with a drive mechanism 8 for the blades, it is advantageous to direct the air flow also through the rotating casing 5, as illustrated in FIG. 3. This makes it possible to ensure that the temperature of the space in which the drive mechanism is installed remains sufficiently low. In some installations, the drive mechanism 8 can also be cooled by a separate cooling fluid (not illustrated). However, even in this case it is advantageous to ensure that the temperature of the internal space of the rotating casing 5 is at an acceptable level by a cooling gas flow, since with fluid cooling it is easier to keep the most important components in the rotating casing at an appropriate temperature.

[0018]

[0022] In Figure 3, an opening 22 through the rotor 4 is provided adjacent the rotating shaft 6. This opening 22 facilitates gas flow from above through the rotor 4 into the rotating casing 5 and back. This opening 22 may be quite large to facilitate the ability of maintenance personnel to enter the rotating casing 5 through this opening 22 for inspection purposes.

[0019]

[0023] 3, the inlet 12 is located close to the axis of rotation 6, while the outlet(s) 13 are located closer to the periphery of the rotor 4. One advantage of this is that the cooled gas flow entering the electric motor via a heat exchanger 14 close to the axis of rotation 6 keeps the ambient temperature of the slip ring unit 16 and the drive mechanism 8 of the blades 7 lower. However, in some installations the direction of gas flow may be opposite, with the inlet(s) at the periphery of the rotor and the outlet(s) near the axis of rotation.

[0020]

[0024] 3, the heat exchanger 14 is located after the fan(s) 15 in the flow direction. However, this is merely an example. In other implementations, the heat exchanger 14 may be located before the fan(s) 15 in the flow direction. In yet some other implementations, the gas flow may be arranged such that the gas is pumped into the outer circulation at the top of the electric motor and flows downward through the air gap 20 into the electric motor in the opposite direction compared to FIG.

[0021]

[0025] Figure 4 illustrates a second embodiment of an electric motor 31. The embodiment of Figure 4 is very similar to the first embodiment described in relation to Figures 1 to 3. Therefore, in the following, the embodiment of Figure 4 will be described mainly by pointing out the differences from these embodiments.

[0022]

[0026] In FIG. 4, the gas flow is directed differently from the inlet 12 to the outlet 13. The wall 23 shown in FIG. 3 is absent in FIG. 4. Due to this, there is nothing forcing the gas flow to pass through the openings 19 (if provided) and the annular gap 20 in the rotor 4. Instead, the gas flow passes from the space above the rotor 4 to the space below the rotor, through the openings 22, along the slip ring unit 16 in the vicinity of the rotation axis 6. However, if an air flow through the openings 19 to the space below the rotor 4 is preferred, this can be obtained in some implementations by reversing the flow direction and positioning the openings 13 above the openings 19. In this case, the gas flow enters the electric motor through the openings 13 and part of the gas flow passes through the openings 19 to the space below the rotor 4.

[0023]

[0027] If the electric motor 31 is used in a cycloidal propulsion unit, the rotating casing 5 and the devices located inside it may be similar to those described in relation to Fig. 3. For simplicity, only the upper part of the rotating casing is shown in Fig. 4, but also in this second embodiment the gas flow may reach devices installed in the rotating casing 5 and provide them with cooling.

[0024]

[0028] Figure 5 illustrates a third embodiment of an electric motor. Figure 5 is very similar to the first embodiment described in relation to Figures 1 to 3 and the second embodiment described in relation to Figure 4. Therefore, in the following, the embodiment of Figure 5 will be described mainly by pointing out the differences from these embodiments.

[0025]

[0029] In FIG. 5, the electric motor 41 is provided with two inlets 12 and also two heat exchangers 14 providing a cooled gas flow to the electric motor 41. Furthermore, two ducts 21 are provided for passing the gas flow leaving the outlet 13 to the respective inlets 12 to provide a closed circulation. The advantage of such a solution, which can also be used in the previously described embodiment, is that the cooling capacity is increased. As a result, a larger amount of cooling gas at a suitable temperature can be provided in the stator of the electric motor 41 compared to the solutions illustrated in FIGS. 3 and 4. Furthermore, such a solution makes the system more redundant in case of failure, such as in case of failure of the fan motor. It also allows the use of smaller components (fans and / or heat exchangers), which saves space.

[0026]

[0030] As can be seen from figure 5, the rotor 4 has a diameter D which is greater than its length L in the direction of the axis of rotation 6. This can also be applied to all other embodiments.

[0027]

[0031] If the electric motor 41 is used in a cycloidal propulsion unit, the rotating casing 5 and the devices located inside it may be similar to those described in relation to Fig. 3. For simplicity, only the upper part of the rotating casing is shown in Fig. 5, but also in this second embodiment the gas flow may reach devices installed in the rotating casing 5 and provide them with cooling.

[0028]

[0032] 6 and 7 illustrate a fourth embodiment of the electric motor.

[0029]

[0033] The embodiment of Figures 6 and 7 is very similar to the first embodiment described in relation to Figures 1 to 3. Therefore, in the following, the embodiment of Figures 6 and 7 will be described mainly by pointing out the differences from these embodiments.

[0030]

[0034] In Figure 6, only the upper right portion of the electric motor is illustrated to provide an enlarged view of the area around the annular gap 20 between the magnets 17 of the rotor 54 and the windings 18 of the stator 2. Figure 7 illustrates an enlarged view of the same area from above.

[0031]

[0035] 6 and 7, as in the embodiment of FIG. 3, the cooling gas flow passes through the annular gap 20 between the rotor 54 and the windings 18 of the stator 2. However, in order to further improve the cooling of the rotor 54, the rotor 54 is provided with holes 55 along its outer periphery. In practice, these holes 55 may form channels extending in a direction parallel or substantially parallel to the direction of the axis of rotation 6.

[0032]

[0036] In figures 6 and 7, it is assumed by way of example that the electric motor is of the type in which the rotor 54 is provided with magnets 17. In that case, holes 55 or channels are provided through the rotor in the magnets 17. In practice, these holes 55 are provided in close proximity to the magnets, between them and the openings 19. With such a solution, a cooling flow in the direction of the rotation axis 6 is obtained on two sides of the magnets 17, via the annular gap 20 and via the holes 55 in the magnets. This makes the cooling even more efficient.

[0033]

[0037] However, if the electric motor is of the type where the rotor is not provided with magnets, such as in the case of an induction motor, it is still beneficial to have the illustrated holes 55 close to the outer periphery of the rotor 54 in order to provide a cooling flow through the holes 55 in the direction of the rotation axis 6. In that case, the holes 55 can be, for example, as close as possible to the cage of the induction motor. Especially for low-cost induction motors, the heat losses are significant and efficient cooling is required. This can be achieved by the structure illustrated in Figures 6 and 7 with the combination of holes 55 in the rotor 54 and an annular gap between the rotor 54 and the stator 2. It can be beneficial to have the holes in two circles in close proximity to the cage of the induction motor to maximize the surface area of ​​the holes.

[0034]

[0038] Figure 8 illustrates a fifth embodiment of an electric motor. The embodiment of Figure 8 is very similar to those described in relation to Figures 1 to 3. Therefore, in the following, the embodiment of Figure 8 will be described mainly by pointing out the differences from these embodiments.

[0035]

[0039] In Fig. 8 the electric motor 61 is installed in an enclosed room 63 (or space), for example of a ship or a building. The room 63 is connected to the ventilation system of the ship or building via an outlet 64 and an inlet 65. A separate heat exchanger for cooling the gas flow passed through the electric motor 61 is therefore not needed for the electric motor, since such a heat exchanger for cooling the gas flow is provided in the ventilation system. One advantage of such a solution is the space saving. In a cycloidal propulsion unit, for example, this can be an important advantage.

[0036]

[0040] 8, it is assumed by way of example that the electric motor 61 is provided with a fan 15 which generates a gas flow into the electric motor 61. However, this fan can be omitted if the air flow into the room from the inlet 65 provides a sufficiently strong air flow, and this inlet 65 can be directly connected to the inlet 12 of the electric motor 61.

[0037]

[0041] In FIG. 8, the outlet 13 from the stator 62 is not provided at the top of the stator, but instead at the side of the stator. In this case, two outlets are provided. A first outlet is provided directly below the stator windings 18, and a second outlet is provided directly above the stator windings 18. In this way, the ends 66 of the stator windings are also efficiently cooled. Due to the location of the bottom outlet 13 below the stator windings 18, the gas flow enters the space below the rotor 4 through the openings 19. In some implementations, it may be advantageous to have several outlets 13 in one or more rows around the side of the stator. In this case, the outlets of this one or more rows of the motor casing may be aligned with the winding ends at both ends of the electric motor.

[0038]

[0042] In Fig. 8, the outlet 13 is arranged in close proximity to the cooling space 11 in which a cooling fluid circulation is provided for cooling the stator 62. This makes it possible to provide cooling fins (not illustrated) extending from the cooling space 11 in the gas flow passing through the outlet 13. In this way, the gas flow can be partially cooled by the cooling fluid circulation in the cooling space 11. Such cooling of the gas flow can also be obtained by reversing the gas flow in the electric motor 61. In that case, the inlet 12 and the outlet 13 are interchanged. As a result, the gas flow entering the electric motor through an inlet at the side of the stator is cooled by the fins in the cooling space 11 just before entering the electric motor.

[0039]

[0043] The inlet or outlet may be provided on the side of the stator 62, as illustrated in Figure 8 and also in the previous embodiment, in which case the electric motor may still be provided with the aforementioned fan and heat exchanger, as described in the previous embodiment.

[0040]

[0044] If the electric motor 61 is used in a cycloidal propulsion unit, the rotating casing 5 and the devices located inside it may be similar to those described in relation to Fig. 3. For simplicity, only the upper part of the rotating casing is shown in Fig. 8, but also in this second embodiment the gas flow may reach devices installed in the rotating casing 5 and provide them with cooling.

[0041]

[0045] It should be understood that the above description and accompanying figures are only intended to illustrate the present invention. It will be apparent to one skilled in the art that changes and modifications can be made to the present invention without departing from the scope of the invention.

Claims

1. An apparatus comprising a cycloidal propulsion unit having an electric motor (1, 31, 41, 51, 61) with a stator (2, 32, 62) and a rotor (4, 54), a cooling space (11) provided in the stator (2, 32, 62) for receiving and passing a cooling fluid for cooling the stator; an inlet (12) and an outlet (13) provided in the electric motor for receiving and passing a cooling gas flow which cools at least the rotor (4, 54) before leaving the electric motor; The electric motor is provided with a dual cooling system including:

2. 2. The apparatus of claim 1, further comprising a fan (15) for circulating the cooling gas flow from the inlet (12) to the outlet (13).

3. 3. The apparatus of claim 1 or 2, comprising a heat exchanger (14) through which the cooling gas flow passes, the heat exchanger (14) receiving and passing a cooling fluid that cools the cooling gas flow in the heat exchanger.

4. 4. The apparatus according to claim 1, wherein an annular gap (20) is provided between an outer periphery of the rotor (4, 54) and the stator (2), and the cooling gas flow between the inlet (12) and the outlet (13) is directed to pass through the annular gap (20).

5. An apparatus as claimed in any one of the preceding claims, wherein the cooling gas flow is directed to flow through at least one opening (19, 22) in the rotor (4, 54) before exiting the electric motor (1).

6. The rotor (54) is provided with holes (55) along its outer periphery and is configured to rotate about a rotation axis (6); the cooling gas flow is directed to flow between the inlet (12) and the outlet (13) by passing through holes (55) in the rotor (54) located in close proximity to the outer periphery of the rotor (54); An apparatus according to any one of claims 1 to 5.

7. The apparatus according to any one of claims 1 to 6, wherein one of the inlet (12) and the outlet (13) is provided in proximity to the cooling space (11) such that cooling fluid in the cooling space (11) cools the cooling gas flow entering or exiting the electric motor (61).

8. The device according to any one of the preceding claims, wherein the cooling space (11) provided in the stator (2, 32, 62) comprises a cooling jacket at least partially surrounding the stator (2, 32, 62).

9. The device according to any one of the preceding claims, wherein the cooling space (11) provided in the stator (2, 32, 62) comprises a cooling tube provided in the stator (2, 32, 62).

10. said cycloidal propulsion unit comprising a rotating casing (5) arranged coaxially with said rotor (4, 54) and as an extension to said stator (2, 32, 62) for rotation therewith about a vertical axis of rotation (6); the rotating casing (5) is provided with a drive mechanism (8) arranged to rotate the blades (7) of the cycloidal propulsion unit protruding outwardly from the rotating casing (5) in a direction away from the rotor (4, 54); An apparatus according to any one of claims 1 to 9.

11. 11. The apparatus of claim 10, wherein at least a portion of the cooling gas flow is directed to flow from the inlet (12) through the rotating casing (5) to the outlet (13) for cooling the drive mechanism.

12. 12. Apparatus according to claim 10 or 11, wherein the rotor (4, 54) is provided with an opening (22) providing access for service personnel to enter the rotating casing (5) by passing through the stator.

13. The device according to any one of the preceding claims, wherein the rotor (4, 54) has a diameter (D) greater than its length (L) in the direction of the axis of rotation (6).

14. A method for cooling an electric motor (1, 31, 41, 51, 61) having a stator (2, 32, 62) and a rotor (4, 54), comprising: circulating a cooling fluid through the stator (2, 32, 62) to cool the stator; Passing a flow of cooling gas into the electric motor (1, 31, 41, 51, 61) via an inlet (12), through the rotor (4, 54) and out of the electric motor via an outlet (13); 16. A method according to claim 15, further comprising providing dual cooling by

15. 15. The method of claim 14, wherein the cooling gas flow is directed along an outer periphery of the rotor (4, 54) and through an annular gap (20) provided between the rotor and the stator (2).

16. 16. The method of claim 14 or 15, wherein the flow of cooling gas is directed along the circumference of the rotor (54) and through holes (55) provided in the rotor (54).

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