Apparatus and method for cooling

Abstract

The invention relates to an apparatus and a method for cooling. The invention relates to a device and a method for cooling an electric motor. In order to achieve simple and sufficient cooling, the electric motor is provided with a dual cooling system comprising a cooling space (11) provided to the stator (2) for receiving and delivering a cooling fluid for cooling the stator, and an inlet (12) and an outlet (13) provided to the electric motor for receiving and delivering a cooling airflow, the cooling air flow cools at least the rotor (4) before leaving the electric motor.

Description

Technical Field

[0001] The present invention relates to a solution for cooling an electric motor. In the following, the invention will be explained by way of example with reference to an electric motor of a cycloidal propulsion unit, although the cooling method may also be used for other electric motors. Background Art

[0002] A problem with electric motors, such as those of gerotor propulsion units, is providing adequate cooling to the various components of the electric motor. Adequate cooling is essential because the load on the electric motor increases if a temperature rise can be avoided. Therefore, if the cooling is effective, more power can be obtained from the electric motor without increasing the diameter or length of the motor. Summary of the invention

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

[0004] By circulating a cooling fluid to the stator, and cooling other components of the electric motor with a cooling air flow, which enters the electric motor from an inlet and flows along the rotor before leaving the electric motor via an outlet, efficient double cooling of the electric motor can be obtained. This solution ensures that the cooling is efficient enough to ensure that a lot of power can be obtained from the electric motor without increasing the size of the electric motor.

[0005] Preferred embodiments of the invention are disclosed in the dependent claims. BRIEF DESCRIPTION OF THE DRAWINGS

[0006] The apparatus and method will be described in more detail below by way of example and with reference to the accompanying drawings, in which

[0007] Figures 1 to 3 The diagram shows an electric motor installed in a cycloidal propulsion unit.

[0008] Figure 4 A second embodiment of the electric motor is shown.

[0009] Figure 5 A third embodiment of an electric motor is shown.

[0010] Figure 6 and Figure 7 A fourth embodiment of an electric motor is shown, and

[0011] Figure 8 A fifth embodiment of the electric motor is shown. DETAILED DESCRIPTION

[0012] Figures 1 to 3The diagram shows an electric motor installed in a cycloidal propulsion unit, such as Figure 1 Side view of Figure 2 The top view and Figure 3 A cross-sectional view with cooling equipment was added to .

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

[0014] The lower part of the hollow rotating sleeve 5 is provided with blades 7, which are located in the water outside the hull 3 and which rotate together with the rotating sleeve around the rotation axis 6. Each blade is additionally provided with a drive mechanism 8, which causes the blade 7 to rotate individually relative to the rotating sleeve 5 around the rotation axis 9. Due to the specific drive mechanism 8 of the blades 7, each blade can be individually controlled to rotate in an optimal manner. This makes it possible to drive and operate the ship using a cycloidal propulsion unit. Therefore, the electric motor shown in the figure can be the main motor of the ship. For example, the drive mechanism can be implemented with suitable mechanical devices, such as gears and shafts. However, in the following explanation, it will be 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. Therefore, each blade 7 has an electric motor. For example, the motor drive 10 can be installed in the rotating sleeve 5.

[0015] A challenge facing an electric motor 1 of the type shown is cooling. In the example shown, a hybrid cooling solution is used to cool the electric motor 1. The hybrid cooling solution comprises a cooling space 11 provided to the stator 2 for receiving and delivering a cooling fluid for cooling the stator. Furthermore, the electric motor 1 is provided with an inlet 12 and an outlet 13 for receiving and delivering a cooling air flow in the stator casing of the electric motor to cool at least the rotor 4. For simplicity, Figure 1 and Figure 2 Inlets, outlets, fans, heat exchangers and cooling spaces are not shown.

[0016] For example, the cooling space 11 through which a cooling fluid (such as water) circulates can be implemented as a cooling jacket. In this case, the cooling space 11 can be implemented as a relatively large volume annular container surrounding at least a portion of the stator 2. Alternatively, according to an embodiment, the cooling space can be implemented as one or more tubes partially surrounding the stator. The cooling space can be implemented as a separate component surrounding and contacting the outer surface of the stator, or alternatively, as a component integrated into the outer wall of the stator casing. If integrated into the outer wall, the wall of the stator is at least partially hollow.

[0017] exist Figure 3 In the embodiment, it is assumed by way of example that a heat exchanger 14 is arranged to cool a flow of air, such as an air flow, entering the electric motor 1 via the inlet 12. Preferably, the heat exchanger is at least partially embedded in the illustrated electric motor. This ensures a compact design that saves space. However, a heat exchanger is not necessary in all embodiments. Figure 3 In the embodiment, the heat exchanger is connected to a fluid circulation, wherein a cold fluid is used to cool the gas entering the electric motor 1. This gas flow circulates inside the electric motor 1, where it comes into contact with at least the rotor 2 before leaving the electric motor via the outlet 13. In the illustrated example, the ton provides two outlets by way of example, although in some embodiments, one outlet may be sufficient. Figure 3 The example in also shows that both outlets 13 are provided with fans 15, such as centrifugal fans, although only one fan may be sufficient. In some embodiments, if the fluid flow can be generated elsewhere, such as by a ventilation system of a building or ship that can generate the airflow required for cooling, a fan may not be needed at all. If a fan is included, it is preferably also at least partially embedded in the illustrated electric motor to provide a compact design.

[0018] exist Figure 3 In the embodiment of the present invention, a closed loop for circulating an air flow from the outlet 13 to the inlet 12 is implemented by means of a duct 21, which feeds the hot air flow from the outlet 13 back to the electric motor 1 via the heat exchanger 14. In addition to cooling the rotor 2, the air flow can also cool the slip ring unit 16, the magnets 17 of the rotor and the windings 18 of the stator 2. The main bearing 29 rotatably supporting the rotor and the rotating sleeve 5 is additionally cooled to some extent by means of the air flow, although the main bearing can be additionally provided with a lubrication feed, which also cools the main bearing.

[0019] By conducting the air flow through the rotor 4 via at least one opening 19, Figure 3 Effective cooling of the magnets and windings is achieved in the rotor 4. The opening is located between the magnet 17 and the axis of rotation 6. In addition, the air flow is conducted through an annular gap 20 formed along the outer circumference of the rotor 4. The annular gap is formed at Figure 3 4 and 4. The motor 20 is shown in the figure, located between the magnets 17 of the rotor 4 and the windings 18 of the stator 2. In order to ensure that the airflow passes through the at least one opening 19 and the annular gap 20, a wall 23 is provided extending from a position near the outer periphery of the rotor 4 to the upper wall part of the motor. The wall 23 prevents the airflow from flowing directly from the inlet to the outlet without flowing through the rotor 4 and the annular gap 20.

[0020] If in Figures 1 to 3In other embodiments, another type of electric motor is used, such as an induction motor with a wound or squirrel cage induction rotor, without magnets in the rotor. In this case, it is also advantageous to conduct the airflow through the annular gap 20 formed along the outer circumference of the rotor 4, because in this case the airflow will cool the wound or squirrel cage rotor.

[0021] When the electric motor 1 is used in a cycloidal propulsion unit, in which the rotating sleeve comprises the drive mechanism 8 for the blades, it is advantageous to conduct the air flow through the rotating sleeve 5, such as Figure 3 As shown. This makes it possible to ensure that the temperature in the space in which the drive mechanism is installed remains sufficiently low. In some installations, the drive mechanism 8 can additionally be cooled by a separate cooling fluid (not shown). However, also in this case, it is advantageous to ensure that the temperature in the interior space of the rotating sleeve 5 is at an acceptable level by means of a cooling air flow, since fluid cooling makes it easier to keep the most critical components in the rotating sleeve at an appropriate temperature.

[0022] exist Figure 3 In the embodiment, an opening 22 through the rotor 4 is provided near the rotation axis 6. The opening 22 facilitates the flow of gas from above through the rotor 4 into the rotating casing 5 and back. The opening 22 can be very large so that maintenance personnel can enter the rotating casing 5 through the opening 22 for maintenance purposes.

[0023] exist Figure 3 In the embodiment of the present invention, the inlet 12 is located close to the rotation axis 6, while the one or more outlets 13 are located closer to the periphery of the rotor 4. One advantage of this is that the cooling air flow entering the electric motor via the heat exchanger 14 close to the rotation axis 6 keeps the ambient temperature of the slip ring unit 16 and the blade 7 drive mechanism 8 low. However, in some installations, the direction of the air flow can be opposite to the one or more inlets located at the periphery of the rotor and the one or more outlets close to the rotation axis.

[0024] exist Figure 3 In the embodiment, the heat exchanger 14 is located after the one or more fans 15 in the flow direction. However, this is explained by way of example only. In other embodiments, the heat exchanger 14 may be located before the one or more fans 15 in the flow direction. In still some other embodiments, the air flow may be arranged so that the gas is fed to an external circulation on top of the electric motor and with Figure 3 In contrast, the gas flows in the opposite direction through the air gap 20 downwards into the electric motor.

[0025] Figure 4 A second embodiment of the electric motor 31 is shown. Figure 4 An embodiment is very similar to combining Figures 1 to 3Therefore, in the following, the first embodiment of the present invention will be mainly explained by pointing out the differences between these embodiments. Figure 4 Embodiment of the invention.

[0026] exist Figure 4 In the embodiment, the air flow from the inlet 12 to the outlet 13 is conducted in different ways. Figure 3 The wall 23 shown is Figure 4 . Therefore, there is nothing to force the airflow to pass through the opening 19 (if any) and the annular gap 20 of the rotor 4. Instead, the airflow flows from the space above the rotor 4 via the opening 22 along the slip ring unit 16 near the axis of rotation 6 to the space below the rotor. However, if it is preferred that the airflow reaches the space below the rotor 4 through the opening 19, in some embodiments, this can be obtained by reversing the flow direction and by positioning the opening 13 above the opening 19. In this case, the airflow enters the electric motor via the opening 13, and part of the airflow continues to enter the space below the rotor 4 via the opening 19.

[0027] If the electric motor 31 is used in a cycloidal propulsion unit, the rotating sleeve 5 and the equipment inside the rotating sleeve can be similar to the combination Figure 3 For simplicity, Figure 4 Only the upper part of the rotating sleeve is shown in FIG. 5 , although in this second embodiment the air flow can also reach the equipment installed in the rotating sleeve 5 and provide cooling for them.

[0028] Figure 5 A third embodiment of an electric motor is shown. Figure 5 Very similar to combining Figures 1 to 3 The first embodiment explained and combined Figure 4 Therefore, in the following, the second embodiment of the present invention will be mainly explained by pointing out the differences between these embodiments. Figure 5 Embodiment of the invention.

[0029] exist Figure 5 In the embodiment, the electric motor 41 is provided with two inlets 12 and two heat exchangers 14, providing a cooling airflow to the electric motor 41. Furthermore, in order to provide a closed loop, two ducts 21 are provided to transfer the airflow leaving the outlet 13 to the corresponding inlet 12. One advantage of this solution is that the cooling capacity is improved, and this solution can also be used in the embodiment explained above. Figure 3 and Figure 4 Compared to the solution shown, a larger amount of cooling gas with a suitable temperature can be provided to the stator of the electric motor 41. Moreover, with this solution, the system becomes more redundant in the event of a fault, such as in the event of a fan motor failure. It also becomes possible to use smaller components (fan and / or heat exchanger) that save space.

[0030] like Figure 5 As shown, the diameter D of the rotor 4 is greater than the length L of the rotor in the direction of the axis of rotation 6 . This also applies to all other exemplary embodiments.

[0031] If the electric motor 41 is used for the cycloidal propulsion unit, the rotating sleeve 5 and the equipment inside the rotating sleeve can be similar to the combination Figure 3 For simplicity, Figure 5 Only the upper part of the rotating sleeve is shown in FIG. 5 , although in this second embodiment the air flow can also reach the equipment installed in the rotating sleeve 5 and provide cooling for them.

[0032] Figure 6 and Figure 7 A fourth embodiment of an electric motor is shown.

[0033] Figure 6 and Figure 7 An embodiment is very similar to combining Figures 1 to 3 Therefore, in the following, the first embodiment of the present invention will be mainly explained by pointing out the differences between these embodiments. Figure 6 and Figure 7 Embodiment of the invention.

[0034] exist 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 rotor 54 magnets 17 and the stator 2 windings 18. Figure 7 An enlarged view of the same area seen from above is shown.

[0035] Similarly, as in Figure 3 In the embodiment of Figure 6 and Figure 7 In the embodiment of the present invention, the cooling air flow passes through the annular gap 20 between the rotor 54 and the stator 2 windings 18. However, in order to still improve the cooling of the rotor, the rotor 54 is provided with holes 55 along the outer circumference of the rotor 54. In practice, these holes 55 can form channels extending in a direction parallel or substantially parallel to the rotation axis 6.

[0036] exist Figure 6 and Figure 7 In , 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 this case, holes 55 or channels are provided through the rotor at the magnets 17. In practice, these holes 55 are provided in the vicinity of the magnets, between the magnets 17 and the openings 19. With this solution, a cooling flow is obtained on both sides of the magnets 17, via the annular gap 20 and the holes 55 at the magnets, flowing in the direction of the axis of rotation 6. This makes the cooling more effective.

[0037] However, in the case where the electric motor is of a type in which the rotor is not provided with magnets, such as in the case of an induction motor, it is still beneficial to place the holes 55 shown close to the periphery of the rotor 54 to provide a cooling flow through the holes 55 in the direction of the axis of rotation 6. In this case, for example, the holes 55 can be placed as close as possible to the squirrel cage induction motor. Especially for low-cost induction motors, the heat losses are significant and effective cooling is required. This can be achieved by Figure 6 and Figure 7 This is achieved with the illustrated structure having a combination of holes 55 in the rotor 52 and an annular gap between the rotor 54 and the stator 2. It may be beneficial to maximise the surface area of ​​the holes by having the holes in two circles close to the squirrel cage induction motor.

[0038] Figure 8 A fifth embodiment of the electric motor is shown. Figure 8 An embodiment is very similar to combining Figures 1 to 3 Therefore, in the following, the present invention will be mainly explained by pointing out the differences between these embodiments. Figure 8 Embodiment of the invention.

[0039] exist Figure 8 In the embodiment, the electric motor 61 is installed in a closed room 63 (or space) of a ship or a building. The room 63 is connected to the ventilation system of the ship or the building via an outlet 64 and an inlet 65. Therefore, no separate heat exchanger is needed at the electric motor to cool the airflow entering the electric motor 61, because such a heat exchanger for cooling the airflow is provided to the ventilation system. One advantage of this solution is that it saves space. For example, in a cycloidal propulsion unit, this can be a significant advantage.

[0040] exist Figure 8 In the embodiment, it is assumed by way of example that the electric motor 61 is provided with a fan 15 which generates an air flow into the electric motor 61. However, in the case where the air flow from the inlet 65 to the room provides a sufficiently strong air flow, the fan can be eliminated and the inlet 65 can be directly connected to the inlet 12 of the electric motor 61.

[0041] exist Figure 8In the embodiment of the present invention, the outlet 13 from the stator 62 is not provided in the upper part of the stator, but is provided on the side of the stator. In this case, two outlets are provided. The first outlet is provided just below the stator winding 18 and the second outlet is provided just above the stator winding 18. In this way, the ends 66 of the stator winding will also be effectively cooled. Since the lower outlet 13 is located below the stator winding 18, the air flow will enter the space below the rotor 4 through the opening 19. In some embodiments, it may be advantageous to have one or more rows of outlets 13 around the side of the stator. In this case, this row or rows of outlets in the motor casing may be aligned with the winding ends on both ends of the electric motor.

[0042] exist Figure 8 In the embodiment of the present invention, the outlet 13 is arranged near the cooling space 11, which is provided with a cooling fluid circulation to cool the stator 62. This makes it possible to provide cooling fins (not shown) to extend from the cooling space 11 into the air flow via the outlet 13. In this way, the air flow can be partially cooled by means of the cooling fluid circulation in the cooling space 11. Such cooling of the air flow can also be obtained by reversing the air flow in the electric motor 61. In this case, the inlet 12 and the outlet 13 exchange positions. Therefore, the air flow entering the electric motor via the inlet on the stator side is cooled by the fins at the cooling space 11 before entering the electric motor.

[0043] An inlet or outlet may be provided on the side of the stator 62, such as Figure 8 As shown, also in the embodiment explained above. In this case, the electric motor can still be provided with the aforementioned fan and heat exchanger, as explained in the aforementioned embodiment.

[0044] If the electric motor 61 is used in a cycloidal propulsion unit, the rotating sleeve 5 and the equipment inside the rotating sleeve can be similar to the combination Figure 3 For simplicity, Figure 8 Only the upper part of the rotating sleeve is shown in FIG. 5 , although in this second embodiment the air flow can also reach the equipment installed in the rotating sleeve 5 and provide cooling for them.

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

Claims

1. A device comprising: A cycloidal propulsion unit having an electric motor (1, 31, 41, 51, 61) having a stator (2, 32, 62) and a rotor (4, 54), characterized in that the electric motor is provided with a double cooling system, the double cooling system comprising: a cooling space (11) provided to the stator (2, 32, 62) for receiving and delivering a cooling fluid for cooling the stator, and An inlet (12) and an outlet (13) are provided to the electric motor for receiving and delivering a cooling airflow which cools at least the rotor (4, 54) before exiting the electric motor.

2. The device according to claim 1, wherein the device comprises a fan (15) which circulates the cooling air flow from the inlet (12) to the outlet (13).

3. The device according to claim 1, wherein the device comprises a heat exchanger (14) through which the cooling air flow passes, the heat exchanger (14) receiving and delivering a cooling fluid, the cooling fluid cooling the cooling air flow in the heat exchanger.

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

5. The device of claim 1, wherein the airflow is directed to flow through at least one opening (19, 22) in the rotor (4, 54) before exiting the electric motor (1).

6. The device according to claim 1, wherein The rotor (54) is provided with holes (55) along its outer circumference and is configured to rotate about an axis of rotation (6), and The cooling air flow is directed to flow between the inlet (12) and the outlet (13) by passing through the holes (55) in the rotor (54), the holes (55) being provided near the outer periphery of the rotor (54).

7. The device according to claim 1, wherein one of the inlet (12) and the outlet (13) is provided near the cooling space (11) so that the cooling fluid in the cooling space (11) cools the air flow entering or leaving the electric motor (61).

8. The device according to claim 1, wherein the cooling space (11) provided to the stator (2, 32, 62) comprises a cooling jacket at least partially surrounding the stator (2, 32, 62).

9. The device according to claim 1, wherein the cooling space (11) provided to the stator (2, 32, 62) comprises a cooling pipe provided to the stator (2, 32, 62).

10. The device according to claim 1, wherein The cycloid propulsion unit comprises a rotating sleeve (5) which is arranged coaxially with the rotor (4, 54) to rotate together with the rotor around a vertical rotation axis (6) and which serves as an extension of the stator (2, 32, 62), and The rotating sleeve (5) comprises a drive mechanism (8) arranged to rotate blades (7) of the cycloid propulsion unit, the blades protruding outwardly from the rotating sleeve (5) in a direction away from the rotor (4, 54).

11. The device according to claim 10, wherein at least a part of the cooling air flow is guided to flow from the inlet (12) via the rotating sleeve (5) to the outlet (13) for cooling the drive mechanism.

12. The device according to any one of claims 10 to 11, wherein the stator (4, 54) is provided with an opening (22) providing access for service personnel to the rotating sleeve (5) by passing through the stator.

13. The device according to claim 1, wherein the diameter (D) of the rotor (4, 54) is greater than the length (L) of the rotor in the direction of the rotation axis (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), characterized in that: The method comprises providing dual cooling by: circulate a cooling fluid to the stator (2, 32, 62) for cooling the stator, and A cooling air flow is passed into the electric motor (1, 31, 41, 51, 61) via an inlet (12), passes through the rotor (4, 54) and further leaves the electric motor via an outlet (13).

15. Method according to claim 14, wherein the cooling air flow is directed along the outer circumference of the rotor (4, 54) through an annular gap (20) provided between the rotor and the stator (2).

16. The method of claim 14, wherein the cooling air flow is directed to pass through holes (55) provided in the rotor (54) along the outer circumference of the rotor (54).

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