Air-air cooler for large megawatt electric machines

Abstract

This invention discloses an air-to-air cooler for large-megawatt motors, comprising a shell with an open bottom. The shell's interior has a U-shaped partition structure, consisting of a left longitudinal partition, a right longitudinal partition, and a transverse partition. The inner side of the U-shaped partition structure is the air inlet area, the outer side of the left longitudinal partition is the left return air area, the outer side of the right longitudinal partition is the right return air area, and the outer side of the transverse partition is the transition area. Air inlet boxes and air outlet boxes are respectively located on the left and right sides of the shell. A cooling centrifugal fan is installed at the inlet of the air inlet box. An array of heat exchange tubes is arranged inside the shell. A pair of heat exchange centrifugal fans, a left centrifugal fan and a right centrifugal fan, are located in the transition area. This air-to-air cooler for large-megawatt motors, through a specific structural design, possesses higher heat exchange efficiency and stability compared to existing technologies, meeting the heat dissipation requirements of large-megawatt motors and ensuring their long-term stable operation.

Description

Technical Field

[0001] This invention relates to the field of cooler technology, and more specifically to an air-to-air cooler for large megawatt motors. Background Technology

[0002] In fields such as power equipment, rail transportation, and industrial drives, the operational stability of motors is directly related to the reliable operation of the entire system. During operation, core components such as the stator and rotor of a motor generate a large amount of heat due to electromagnetic losses and mechanical friction. If this heat cannot be dissipated effectively and in a timely manner, the internal temperature of the motor will continue to rise, leading to problems such as accelerated aging of insulation materials, increased winding resistance, and decreased output efficiency. In severe cases, it can even cause the motor to burn out, resulting in production accidents and economic losses.

[0003] To address the heat dissipation problem of motors, air-to-air coolers, as heat exchange devices that use ambient air as the cooling medium, are widely used in the cooling systems of various motors due to their relatively simple structure, low maintenance costs, and lack of the need for additional cooling media. A conventional air-to-air cooler mainly consists of a shell, a centrifugal fan, and heat exchange tubes. Its working principle is as follows: the centrifugal fan drives ambient air into the heat exchange tubes, while the hot air inside the motor flows through the outer casing channels of the heat exchange tubes, exchanging heat with the air through the tube walls. The heated external air is then discharged, and the cooled internal air flows back to the motor, achieving the cooling purpose.

[0004] However, with the continuous growth in industrial production's demand for power, the power of equipment such as generators and large drive motors is showing a significant trend towards larger sizes and megawatt levels. Industry data shows that in the past decade, the market demand for megawatt-class and above motors has grown at an average annual rate of over 15%, with single-unit power increasing from a few megawatts to tens or even hundreds of megawatts. This significant increase in motor power directly leads to a geometric increase in the heat exchange required during operation, making it difficult for conventional air-cooled radiators to meet the heat dissipation needs of large megawatt motors (8MW and above). Chinese patent document CN120498174A discloses a labyrinth-type baffle hole group flow-guiding high-efficiency cooling structure radiator, which extends the airflow path and improves heat exchange efficiency by setting labyrinth-type baffles. However, due to the low airflow velocity inside the motor, it still cannot meet the heat dissipation needs of large megawatt motors.

[0005] Against this backdrop, the development of air-to-air coolers for large-megawatt motors has become an urgent need for industry development. Developing air-to-air coolers for large-megawatt motors with higher heat exchange efficiency and stability can not only solve the heat dissipation bottleneck of large-megawatt motors and ensure their long-term stable operation, but also further promote technological upgrades in power equipment, new energy, and other fields, possessing significant economic value and industry significance. Summary of the Invention

[0006] To address the shortcomings of existing technologies, this application provides an air-to-air cooler for large-megawatt motors. This air-to-air cooler for large-megawatt motors, through a specific structural design, exhibits higher heat exchange efficiency and stability compared to existing technologies, meeting the heat dissipation requirements of large-megawatt motors and ensuring their long-term stable operation.

[0007] To achieve the above-mentioned objectives, this application provides the following technical solution:

[0008] An air-cooled chiller for a large megawatt motor includes a shell with an open bottom. Inside the shell is a U-shaped partition structure, consisting of a left longitudinal partition, a right longitudinal partition, and transverse partitions. The inner side of the U-shaped partition structure is the air inlet area, the outer side of the left longitudinal partition is the left return air area, the outer side of the right longitudinal partition is the right return air area, and the outer side of the transverse partition is the transition area. Air inlet boxes and air outlet boxes are respectively located on the left and right sides of the shell. A cooling centrifugal fan is installed at the inlet of the air inlet box. An array of heat exchange tubes is arranged inside the shell, with one end of each heat exchange tube connected to the air inlet box and the other end connected to the air outlet box. The cooling centrifugal fan... The fan is used to send external cold air into the heat exchange tubes, and after heat exchange, it is discharged from the air outlet box. A pair of heat exchange centrifugal fans are provided in the transition zone, namely a left centrifugal fan and a right centrifugal fan. The inlets of the left and right centrifugal fans are both located on the horizontal partition. The outlet of the left centrifugal fan faces the left end of the shell, and the outlet of the right centrifugal fan faces the right end of the shell. When the heat exchange centrifugal fans are working, the hot air inside the megawatt motor is drawn into the air inlet zone. Part of it flows back to the megawatt motor through the transition zone and the left return air zone, forming a left circulation loop. The other part flows back to the megawatt motor through the transition zone and the right return air zone, forming a right circulation loop.

[0009] When the air cooler of the present invention is working, the cooling centrifugal fan continuously drives the ambient air into the heat exchange tube. The heat exchange centrifugal fan causes the air inside the large megawatt motor to circulate rapidly along the set flow channel and exchange heat through the tube wall. Since the air circulation efficiency inside the large megawatt motor is high, the heat dissipation efficiency is greatly improved.

[0010] As an optimization, in the aforementioned air-cooled system for large-megawatt motors, the left return air zone is equipped with a return air splitter plate A, which divides the airflow entering the left return air zone into upper and lower parts. The length L1 of the return air splitter plate A is equivalent to 50-60% of the length L2 of the left return air zone. Similarly, the right return air zone is equipped with a return air splitter plate B, which divides the airflow entering the right return air zone into upper and lower parts. The length L3 of the return air splitter plate B is equivalent to 50-60% of the length L4 of the left return air zone. The splitter plates guide a portion of the airflow to the side away from the transverse partition and back into the large-megawatt motor, thereby enabling uniform heat dissipation, minimizing the temperature difference between the two sides, and preventing localized overheating. Furthermore, during operation, the airflow deviation between the upper and lower sides of the return air splitter plate A and the return air splitter plate B does not exceed 10%.

[0011] As an optimization, in the aforementioned air-cooled unit for large-megawatt motors, an air inlet diverter is provided between the left and right longitudinal partitions. This diverter divides the inlet of the heat exchange centrifugal fan in two, and its length is equivalent to 40-60% of the length of the air inlet zone. The diverter is designed to ensure more uniform heat dissipation on both sides of the motor shaft. Furthermore, during operation, the flow rate deviation between the upper and lower sides of the diverter does not exceed 10%.

[0012] As an optimization, in the aforementioned air-cooled cooler for large-megawatt motors, noise-reducing guide plates are provided at both ends of the transition zone, corresponding to the outlets of the left and right centrifugal fans, respectively. These guide plates have an arc-shaped structure, ensuring a smooth connection between the transition zone and the left and right return flow zones. The noise-reducing guide plates reduce flow resistance and simultaneously reduce airflow noise. Furthermore, the guide plates are provided with groups of micropores, forming a microporous noise reduction structure with the housing. This structure, through the principle of microporous noise reduction, further reduces airflow noise, making it easier for maintenance personnel to detect minor abnormal noises promptly.

[0013] As an optimization, in the aforementioned air-cooled centrifugal fan for large-megawatt motors, the cooling centrifugal fan includes two sets of volute impeller assemblies, namely volute impeller assembly A and volute impeller assembly B. The volute impeller assembly A is connected to the drive motor, and the impeller shaft of the volute impeller assembly B is connected to the impeller shaft of the volute impeller assembly A via a centrifugal clutch. With this structure, when the large-megawatt motor operates at high power and the heat dissipation demand increases dramatically, the speed of the drive motor can be increased to improve the airflow of the volute impeller assembly A. Simultaneously, the centrifugal clutch engages, driving the impeller of the volute impeller assembly B to rotate, further increasing the airflow and significantly improving heat exchange efficiency. Conversely, when the heat dissipation demand is low, the speed of the drive motor can be reduced to decrease energy consumption. Furthermore, the cooling centrifugal fan has two sets of volute impeller assemblies but only requires one drive motor, which helps control costs.

[0014] As an optimization, in the aforementioned air-cooled unit for large-megawatt motors, the drive motor is fixedly mounted on the side of the A volute impeller assembly. In this case, the component consisting of the drive motor and the A volute impeller assembly is a conventional centrifugal fan, which can be directly purchased, thus helping to control costs. Furthermore, the centrifugal clutch can be mounted on the side of the air inlet box using a mounting bracket. Providing the centrifugal clutch independently is easier to implement than integrating it into the volute impeller assembly, and in this case, the B volute impeller assembly is simply the part of a conventional centrifugal fan after removing the drive motor, which can also be directly purchased, further contributing to cost control.

[0015] As an optimization, in the aforementioned air-cooled system for large-megawatt motors, during operation, if the temperature rise of the large-megawatt motor does not exceed a set value, the controller controls the operating speed of the drive motor to be lower than the engagement threshold of the centrifugal clutch, causing the impeller in the A volute impeller assembly to rotate while the impeller in the B volute impeller assembly remains stationary. If the temperature rise of the large-megawatt motor exceeds the set value, the controller controls the operating speed of the drive motor to be no less than the engagement threshold of the centrifugal clutch, causing the centrifugal clutch to engage, and the impellers in the A and B volute impeller assemblies to rotate synchronously. This specific control logic helps reduce energy consumption. For example, in winter, due to the lower temperature, controlling the drive motor to run at a low speed is sufficient to meet the heat dissipation requirements, thereby reducing energy consumption. In summer, controlling the drive motor to run at a high speed ensures the heat exchange efficiency of the cooler, guaranteeing the stable operation of the large-megawatt motor.

[0016] Compared with the prior art, the present invention has the following beneficial technical effects: The present invention divides the shell into a left return air zone, an air inlet zone, a right return air zone, and a transition zone by a left longitudinal partition, a right longitudinal partition, and a transverse partition. Two heat exchange centrifugal fans are set in the transition zone. Hot air from the large-megawatt motor is drawn into the air inlet zone. Part of the air flows back to the large-megawatt motor through the transition zone and the left return air zone, forming a left circulation loop. The other part flows back to the large-megawatt motor through the transition zone and the right return air zone, forming a right circulation loop. The air inside the large-megawatt motor circulates rapidly, significantly improving the heat dissipation efficiency. Inside the shell, there are A return air diverter plates and B return air diverter plates, and the airflow deviation between the upper and lower sides is controlled to not exceed 10%, making the heat dissipation effect on both halves of the large-megawatt motor more uniform, avoiding local overheating, and facilitating the stable operation of the large-megawatt motor. Inside the shell, there are air inlet diverter plates, and the airflow deviation between the upper and lower sides is controlled to not exceed 10%, which also helps to ensure uniform heat dissipation inside the large-megawatt motor. Furthermore, the two sets of volute impeller assemblies of the cooling centrifugal fan share a single drive motor, and the impellers of the two sets of volute impeller assemblies are connected by a centrifugal clutch, enabling targeted heat dissipation adjustment based on the temperature rise of the megawatt motor to save energy. In addition, the invention also sets an arc-shaped noise-reducing guide plate at the air outlet of the heat exchange centrifugal fan to guide the airflow direction and reduce the generation of eddies during airflow turning, thereby reducing noise and vibration caused by airflow turning. The arc-shaped noise-reducing guide plate is provided with groups of micropores, so that the arc-shaped noise-reducing guide plate and the shell form a microporous noise reduction structure, further reducing airflow noise and vibration. Attached Figure Description

[0017] Figure 1 This is a schematic diagram of the air-cooled cooler used in a large megawatt motor according to this application. Figure 1 ;

[0018] Figure 2 This is a schematic diagram of the air-cooled cooler used in a large megawatt motor according to this application. Figure 2 ;

[0019] Figure 3 yes Figure 1 Top view (with part of the shell removed);

[0020] Figure 4 This is a schematic diagram of the shell structure in this application. Figure 1 ;

[0021] Figure 5 This is a schematic diagram of the shell structure in this application. Figure 2 ;

[0022] Figure 6 yes Figure 5 The front view.

[0023] The labels in the attached diagram are as follows: 1-Shell, 11-Left longitudinal partition, 12-Right longitudinal partition, 13-Transverse partition, 14-Air inlet zone, 15-Left return air zone, 16-Right return air zone, 17-Transition zone, 18a-A return air splitter plate, 18b-B return air splitter plate, 19-Air inlet splitter plate; 2-Air inlet box; 3-Air outlet box; 4-Cooling centrifugal fan, 41-A volute impeller assembly, 42-B volute impeller assembly, 43-Drive motor; 5-Heat exchange tube; 6-Heat exchange centrifugal fan, 61-Left centrifugal fan, 62-Right centrifugal fan; 7-Centrifugal clutch; 8-Noise reduction guide plate; 9-Cavity. Detailed Implementation

[0024] The present application will be further described below with reference to the accompanying drawings and embodiments, but this should not be construed as limiting the present application. In the following embodiments, content not described in detail or shown in detail in the accompanying drawings is common knowledge in the art.

[0025] Example (see) Figures 1-6 ):

[0026] An air-cooled cooler for a large megawatt motor includes a shell 1 with an open bottom. The shell 1 has an internal U-shaped partition structure, which consists of a left longitudinal partition 11, a right longitudinal partition 12, and a transverse partition 13. The inner side of the U-shaped partition structure is the air inlet zone 14, the outer side of the left longitudinal partition 11 is the left return air zone 15, the outer side of the right longitudinal partition 12 is the right return air zone 16, and the outer side of the transverse partition 13 is the transition zone 17. An air inlet box 2 and an air outlet box 3 are respectively located on the left and right sides of the shell 1. A cooling centrifugal fan 4 is installed at the inlet of the air inlet box 2. The interior is equipped with an array of heat exchange tubes 5, one end of which is connected to the air inlet box 2, and the other end is connected to the air outlet box 3. A cooling centrifugal fan 4 is used to send external cold air into the heat exchange tubes 5, which, after heat exchange, is discharged from the air outlet box 3. A pair of heat exchange centrifugal fans 6, namely a left centrifugal fan 61 and a right centrifugal fan 62, are located in the transition zone 17. The inlets of both the left and right centrifugal fans 61 and 62 are located on the transverse partition 13. The outlet of the left centrifugal fan 61 faces the left end of the housing 1, and the outlet of the right centrifugal fan 62 faces the right end of the housing 1. During operation, the heat exchange centrifugal fans 6 promote the circulation of hot air inside the large-megawatt motor, exchanging heat with the cold air inside the heat exchange tubes 5 through the tube walls within the housing 1, thus maintaining a stable temperature rise in the large-megawatt motor.

[0027] In this embodiment, the left return air zone 15 is provided with an A return air diverter plate 18a, which divides the airflow entering the left return air zone 15 into upper and lower parts. The length L1 of the A return air diverter plate 18a is equivalent to 50% of the length L2 of the left return air zone 15. The right return air zone 16 is provided with a B return air diverter plate 18b, which divides the airflow entering the right return air zone 16 into upper and lower parts. The length L3 of the B return air diverter plate 18b is equivalent to 50% of the length L4 of the left return air zone 15. During operation, the airflow deviation between the upper and lower sides of the A return air diverter plate 18a does not exceed 10%, and the airflow deviation between the upper and lower sides of the B return air diverter plate 18b does not exceed 10%. The installation height of the A return air diverter plate 18a and the B return air diverter plate 18b determines the flow deviation (flow imbalance) between their upper and lower sides. In this embodiment, CFD fluid simulation is used to determine the installation height of return air splitter plate A 18a and return air splitter plate B 18b, so that the gas flow rate on the upper and lower sides is theoretically equal (of course, the actual flow rate will deviate from the simulation). During operation, the airflow is divided into two parts, which flow back to the interior of the large megawatt motor from both sides of the large megawatt motor shaft, so that the heat dissipation of the large megawatt motor is uniform.

[0028] In this embodiment, an air inlet diversion plate 19 is provided between the left longitudinal partition 11 and the right longitudinal partition 12. The air inlet diversion plate 19 divides the inlet of the heat exchange centrifugal fan 6 into two parts. The length of the air inlet diversion plate 19 is equivalent to 50% of the length of the air inlet zone 14. The flow rate deviation between the upper and lower sides of the air inlet diversion plate 19 does not exceed 10%. In this embodiment, the installation height of the air inlet diversion plate 19 is determined using CFD fluid simulation to ensure that the gas flow rate on both lower sides is theoretically equal, further improving the heat dissipation uniformity inside the large-megawatt motor.

[0029] In this embodiment, noise-reducing guide plates 8 are provided at both ends of the transition zone 17, corresponding to the outlets of the left centrifugal fan 61 and the right centrifugal fan 62, respectively. The noise-reducing guide plates 8 have an arc-shaped structure, allowing the transition zone 17 to smoothly connect with the left return zone 15 and the right return zone 16. Groups of micropores are provided on the noise-reducing guide plates 8, forming a microporous noise-reducing structure with the housing 1. Using this structure, the arc-shaped guide plates guide the gas flow, reducing flow resistance and thus reducing noise and vibration caused by airflow. Furthermore, the micropores and cavity 9 form a microporous noise-reducing structure, further reducing the noise generated by airflow, making it easier for maintenance personnel to detect minor abnormal noises promptly.

[0030] In this embodiment, the cooling centrifugal fan 4 includes two sets of volute impeller assemblies, namely volute impeller assembly A 41 and volute impeller assembly B 42. volute impeller assembly A 41 is connected to the drive motor 43, and the impeller shaft of volute impeller assembly B 42 is connected to the impeller shaft of volute impeller assembly A 41 through a centrifugal clutch 7. With this structure, when the motor temperature rise is not high, only the A volute impeller assembly 41 can be used to inject cold air into the heat exchange tube 5, thus saving energy. When the A volute impeller assembly 41 alone is insufficient to meet the heat dissipation requirements of a large megawatt motor, the speed of the drive motor 43 can be increased to increase the air supply of the A volute impeller assembly 41. At the same time, the centrifugal clutch 7 engages to drive the impeller of the B volute impeller assembly 42 to rotate. On the one hand, the increased impeller speed increases the air supply of the A volute impeller assembly 41. On the other hand, the addition of the B volute impeller assembly 42 increases the air supply by several times compared to when the A volute impeller assembly 41 works alone, thereby significantly improving the heat exchange efficiency.

[0031] In this embodiment, the drive motor 43 is fixedly mounted on the side of the A volute impeller assembly 41. The component consisting of the drive motor 43 and the A volute impeller assembly 41 is a conventional centrifugal fan, which can be directly purchased.

[0032] In this embodiment, when the air cooler for the large-megawatt motor is installed on the large-megawatt motor, the hot air emitted by the large-megawatt motor enters the housing 1 from the air inlet zone 14. The portion near the heat exchange centrifugal fan 6 flows from below the air inlet diverter plate 19, passes through the gap between the heat exchange tube 5 components and exchanges heat, and then enters the centrifugal fan 6. The portion away from the heat exchange centrifugal fan 6 flows upward from above the air inlet diverter plate 19, passes through the gap between the heat exchange tube 5 components and exchanges heat fully with the heat exchange tube 5, and then enters the centrifugal fan 6. The gas entering the left centrifugal fan 61 is guided by the noise reduction guide plate 8. Part of it returns directly to the large-megawatt motor (the side of the large-megawatt motor closest to the heat exchange centrifugal fan 6) from below the A return air diverter plate 18a, and the other part passes above the A return air diverter plate 18a and then returns to the large-megawatt motor (the side of the large-megawatt motor away from the heat exchange centrifugal fan 6). The same applies to the gas entering the right centrifugal fan 62. Meanwhile, the cooling centrifugal fan 4 sends external cold air into the heat exchange tube 5 to form a cooling medium, and heat exchange occurs through the tube wall of the heat exchange tube 5.

[0033] When the air cooler for the large megawatt motor in this embodiment is working, if the temperature rise of the large megawatt motor does not exceed the set threshold, the controller controls the operating speed of the drive motor 43 to be less than the engagement threshold of the centrifugal clutch 7. At this time, the A volute impeller assembly 41 works, and the B volute impeller assembly 42 does not work. If the temperature rise of the large megawatt motor exceeds the set threshold, the controller controls the operating speed of the drive motor 43 to be not less than the engagement threshold of the centrifugal clutch 7, and the A volute impeller assembly 41 and the B volute impeller assembly 42 work simultaneously.

[0034] In this invention, .in, The gas flow rate on the upper side of the plate. This represents the gas flow rate on the underside of the plate.

[0035] The foregoing general description of the invention and its specific embodiments should not be construed as a limitation on the technical solution of the invention. Those skilled in the art, based on the disclosure of this application, can add, reduce, or combine the disclosed technical features in the foregoing general description and / or specific embodiments (including examples) without departing from the constituent elements of the invention, to form other technical solutions within the scope of protection of this application.

Claims

1. An air cooler for large megawatt motors, characterized in that: The shell (1) includes an open bottom. The shell (1) has a U-shaped partition structure inside. The U-shaped partition structure is composed of a left longitudinal partition (11), a right longitudinal partition (12) and a transverse partition (13). The inner side of the U-shaped partition structure is the air inlet area (14), the outer side of the left longitudinal partition (11) is the left return air area (15), the outer side of the right longitudinal partition (12) is the right return air area (16), and the outer side of the transverse partition (13) is the transition area (17). The shell (1) is provided with an air inlet box (2) and an air outlet box (3) on its left and right sides respectively. The air inlet box (2) is provided with a cooling centrifugal fan (4) at its inlet. The shell (1) is provided with an array of heat exchange tubes (5) inside. One end of the heat exchange tube (5) is connected to the air inlet box (2) and the other end is connected to the air outlet box (3). The cooling centrifugal fan (4) is used to send external cold air into the heat exchange tube (5) and discharge it from the air outlet box (3) after heat exchange. The transition zone (17) is provided with a pair of heat exchange centrifugal fans (6), namely a left centrifugal fan (61) and a right centrifugal fan (62); the inlets of the left centrifugal fan (61) and the right centrifugal fan (62) are both located on the horizontal partition (13), the outlet of the left centrifugal fan (61) faces the left end of the housing (1), and the outlet of the right centrifugal fan (62) faces the right end of the housing (1); when the heat exchange centrifugal fan (6) is working, the hot air inside the megawatt motor is drawn into the air inlet zone (14), part of which flows back to the megawatt motor through the transition zone (17) and the left return air zone (15) to form a left circulation loop, and the other part flows back to the megawatt motor through the transition zone (17) and the right return air zone (16) to form a right circulation loop.

2. The air-cooled cooler for a large megawatt motor according to claim 1, characterized in that: The left return air zone (15) is provided with an A return air splitter plate (18a), which splits the airflow entering the left return air zone (15) into upper and lower parts. The length L1 of the A return air splitter plate (18a) is equivalent to 50-60% of the length L2 of the left return air zone (15). The right return air zone (16) is provided with a B return air splitter plate (18b), which splits the airflow entering the right return air zone (16) into upper and lower parts. The length L3 of the B return air splitter plate (18b) is equivalent to 50-60% of the length L4 of the left return air zone (15).

3. The air-cooled cooler for a large megawatt motor according to claim 2, characterized in that: During operation, the airflow deviation between the upper and lower sides of the A return air diverter plate (18a) does not exceed 10%; the airflow deviation between the upper and lower sides of the B return air diverter plate (18b) does not exceed 10%.

4. The air-cooled cooler for a large megawatt motor according to claim 3, characterized in that: An air inlet diversion plate (19) is provided between the left longitudinal partition (11) and the right longitudinal partition (12). The air inlet diversion plate (19) divides the inlet of the heat exchange centrifugal fan (6) into two parts. The length of the air inlet diversion plate (19) is equivalent to 40-60% of the length of the air inlet zone (14).

5. The air-cooled cooler for a large megawatt motor according to claim 4, characterized in that: The flow rate deviation between the upper and lower sides of the air inlet splitter plate (19) shall not exceed 10%.

6. The air-cooled cooler for a large megawatt motor according to claim 5, characterized in that: The left and right ends of the transition zone (17) are respectively provided with noise reduction guide plates (8) corresponding to the outlets of the left centrifugal fan (61) and the right centrifugal fan (62). The noise reduction guide plates (8) have an arc-shaped structure, so that the transition zone (17) and the left return zone (15) and the right return zone (16) are smoothly connected.

7. The air-cooled cooler for a large megawatt motor according to claim 6, characterized in that: The noise reduction guide plate (8) is provided with micropores in groups, so that the noise reduction guide plate (8) and the shell (1) form a micropore noise reduction structure.

8. The air-cooled cooler for a large megawatt motor according to any one of claims 1-7, characterized in that: The cooling centrifugal fan (4) includes two sets of volute impeller assemblies, namely volute impeller assembly A (41) and volute impeller assembly B (42). volute impeller assembly A (41) is connected to the drive motor (43) via a transmission connection. The impeller shaft of volute impeller assembly B (42) is connected to the impeller shaft of volute impeller assembly A (41) via a centrifugal clutch (7).

9. The air-cooled cooler for a large megawatt motor according to claim 8, characterized in that: The drive motor (43) is fixedly mounted on the side of the A volute impeller assembly (41).

10. The air-cooled cooler for a large megawatt motor according to claim 8 or 9, characterized in that: During operation, if the temperature rise of the large megawatt motor does not exceed the set value, the controller controls the operating speed of the drive motor (43) to be less than the engagement threshold of the centrifugal clutch (7), and the impeller in the A volute impeller assembly (41) rotates while the impeller in the B volute impeller assembly (42) does not rotate; if the temperature rise of the large megawatt motor exceeds the set value, the controller controls the operating speed of the drive motor (43) to be not less than the engagement threshold of the centrifugal clutch (7), so that the centrifugal clutch (7) is engaged and the impellers in the A volute impeller assembly (41) and the B volute impeller assembly (42) rotate synchronously.

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