A main pump motor of a nuclear power unit

Abstract

The application belongs to the technical field of nuclear power plant reactor coolant pump driving equipment, and discloses a main pump motor of a nuclear power unit, which comprises an integrated base, a stator, a rotor, a base, an upper bearing assembly and a lower guide bearing; wherein the upper bearing assembly is installed on the upper end of the base, is an integrated bidirectional thrust bearing and an upper guide bearing, and is used for bearing bidirectional axial load; a flywheel is arranged below the rotor iron core and above the lower guide bearing, i.e. between the two side guide bearings; the base is a four-corner support integrated welded structure, and the shape is an unequal octagon. The application improves the maintenance accessibility by arranging the thrust bearing upward, reduces the gravity center of the motor and the vibration of the whole machine by arranging the flywheel downward and between the two side bearings, and improves the assembly precision and load envelope by the integrated base.

Description

Technical Field

[0001] This invention belongs to the technical field of nuclear power plant reactor coolant pump drive equipment, specifically relating to a main pump motor for a nuclear power unit. Background Technology

[0003] The main nuclear pump has always been one of the most critical pieces of equipment restricting the development of nuclear power plants. Located inside the reactor building, the main nuclear pump is the only actively rotating device in the reactor coolant system. Its function is to drive the coolant circulation in the primary loop, transferring heat from the reactor core to the secondary loop via the steam generator. The main pump motor provides power to the main pump and is an important component of it.

[0004] Compared to traditional vertical asynchronous motors, the main pump motor needs to start under load with a large inertia load, while ensuring long-term reliable and safe operation under various extreme and harsh working conditions. The research and development requires high technical standards and is very difficult, involving multiple disciplines and multiple physical couplings, and has the following characteristics and challenges: ① large inertia flywheel ② safety ③ lifespan requirements ④ withstanding bidirectional large thrust ⑤ three-support long shaft system ⑥ design standardization ⑦ complex system load iteration ⑧ 100% independent development of the entire process.

[0005] Current technical solutions include: ① Rated voltage 6kV level, designed for the structure of a three-bearing main pump, with a bidirectional thrust bearing at the bottom, a three-section frame, and a flywheel at the bottom and located above the lower guide bearing; ② Rated voltage 10kV level, designed for the structure of a four-bearing main pump, with a single-direction thrust bearing on the top, a three-section base, and a flywheel on the bottom, located below the lower guide bearing; ③ Rated voltage level 10kV, designed for the structure of a three-bearing main pump, with a bidirectional thrust bearing on top, a three-section frame, and a flywheel on top, located above the upper guide bearing; The design presents several challenges, including: the thrust bearing being located at the bottom, making on-site maintenance difficult; it only bears unidirectional thrust, placing high demands on the main pump equipment; the flywheel being located at the top, resulting in poor motor vibration stability; and the segmented base causing poor load envelope and complex assembly. Summary of the Invention

[0006] The purpose of this invention is to overcome the shortcomings of the prior art and provide a main pump motor for nuclear power units. By placing the thrust bearing on top, the accessibility for maintenance is improved. By placing the flywheel on the bottom and between the two bearings, the center of gravity of the motor and the vibration of the whole machine are reduced. By using an integrated base, the assembly accuracy and load envelope are improved, thus meeting the requirements of nuclear power plants for high reliability, long service life and easy maintenance of the main pump motor.

[0007] The technical solution to achieve the above objective is: A main pump motor for a nuclear power unit, comprising a frame, stator, rotor, base, terminal box, air-water cooler, upper bearing assembly, lower guide bearing, and anti-reverse device, wherein: The base is an integral welded structure with a four-corner support frame structure and its horizontal cross-section is an unequal-sided octagon. The stator is installed inside the frame; The base is installed at the lower end of the machine base; The outlet box and the air-water cooler are respectively installed on the outside of the base; The upper bearing assembly is installed on the upper end of the machine base and is an integrated assembly of a bidirectional thrust bearing and an upper guide bearing, used to bear the bidirectional axial load and the radial load of the non-shaft extension end of the rotor. The lower guide bearing is installed at the lower end of the machine base and is located inside the base to bear the radial load of the rotor shaft extension end; The rotor is disposed inside the stator. The rotor includes a rotating shaft and, from top to bottom, a top balance disc, an upper balance disc, a rotor core, a lower balance disc, and a flywheel, which are sequentially fitted onto the rotating shaft. The flywheel is disposed below the rotor core and above the lower guide bearing. The upper and lower parts of the rotor are supported one-to-one by the upper bearing assembly and the lower guide bearing; The anti-reverse device is installed on the top of the base and is located below the top balance disc.

[0008] The above-mentioned main pump motor of a nuclear power unit, wherein the upper bearing assembly includes a thrust head, a bearing housing, an upper guide bearing, an upper thrust bearing, a lower thrust bearing, and cooling pipes; wherein: The thrust head, bearing housing, upper thrust pad, and lower thrust pad constitute the core structure of the bidirectional thrust bearing, and the thrust head, bearing housing, and upper guide pad constitute the core structure of the upper guide bearing. The thrust head is mounted on the rotating shaft via a heat-shrinkable sleeve. The upper thrust pad and the lower thrust pad are respectively disposed on the upper and lower sides of the lower part of the thrust head. When the axial thrust is low, the lower thrust pad bears the load, and when the axial thrust is high, the upper thrust pad bears the load. The upper guide plate is installed inside the bearing housing and is located outside the thrust head; The cooling pipes are located outside the bearing housing.

[0009] The cooling pipes are located outside the bearing housing.

[0010] 3. The main pump motor of a nuclear power unit according to claim 1, characterized in that the flywheel is an integral forging structure, connected to the rotating shaft by an interference fit through a bushing, without a keyway, and is provided with a pressure relief structure to achieve adjustable interference; the flywheel adopts a non-detachable design.

[0011] 4. The main pump motor of a nuclear power unit according to claim 1, characterized in that the stator is composed of a stator core and a stator winding, the stator core is made of fan-shaped silicon steel sheets stacked together, with external pressing and stacking, and stator pressure rings fixed at both ends, and 12 channel steels are evenly distributed and welded on the outer circle of the stator core, each channel steel having a ventilation opening; the stator winding is composed of three independent windings, and each winding is composed of several coils connected together, the coils are wound with copper wires covered with insulating material, and the stator winding adopts a low-adhesion insulation system and has radiation resistance.

[0012] 5. The main pump motor of a nuclear power unit according to claim 1, characterized in that the main pump motor adopts a symmetrical ventilation system; air inlets are respectively provided at the upper and lower ends of both sides of the base, and the upper and lower air inlet areas are the same; the ventilation ducts of the stator and rotor are not aligned.

[0013] 6. The main pump motor of a nuclear power unit according to claim 5, characterized in that it further includes an upper baffle plate and a lower baffle plate, the upper baffle plate being disposed at the upper air inlet and located below the upper bearing assembly; the lower baffle plate being disposed at the lower air inlet and located above the flywheel; each bearing and air inlet adopts dynamic and static coupling isolation measures, and the relative structure of the upper baffle plate, lower baffle plate and upper balance plate plays an isolation role, avoiding the bearing gas seal from bearing negative pressure and the risk of oil leakage.

[0014] 7. The main pump motor of a nuclear power unit according to claim 1, characterized in that the inner ring of the anti-reverse device is connected to the rotating shaft, and the outer ring is connected to the stationary part of the motor, and the one-way anti-reverse function is realized by the wedge between the inner and outer rings.

[0015] 8. The main pump motor of a nuclear power unit according to claim 1, characterized in that the rotor shaft is a welded shaft structure; the rotor core is made of stacked whole round silicon steel sheets, and rotor pressure rings are provided at both ends for fixation.

[0016] 9. The main pump motor of a nuclear power unit according to claim 1, characterized in that two centrifugal fans are further installed on the rotating shaft, and the two centrifugal fans are respectively located at both ends of the rotor core.

[0017] The main pump motor of the aforementioned nuclear power unit, wherein the base is welded together from upper and lower walls, a middle side wall, and supporting ribs.

[0018] The main pump motor of the nuclear power unit of the present invention has the following beneficial effects: (1) The bidirectional thrust bearing is located on the top of the motor. While meeting the functional requirements of bearing bidirectional thrust, it has better accessibility, is convenient for on-site inspection and maintenance, and is easy to maintain.

[0019] (2) The flywheel is positioned at the bottom and between the two guide bearings (upper guide bearing and lower guide bearing), which effectively lowers the center of gravity of the motor, reduces the overall vibration of the motor, and makes the shaft system vibration stable, thus reducing shaft vibration. The flywheel is connected by a hot-fitting integral forging without keyways, which avoids stress concentration. At the same time, a pressure relief structure design is adopted to ensure that the interference fit with the shaft is adjustable and easy to disassemble and assemble.

[0020] (3) The electromagnetic design of the motor meets the performance requirements of efficiency, cooling and starting, and meets the start-stop reliability requirements during its service life, with excellent overall performance.

[0021] (4) By taking into account both shaft system optimization and rotor cooling design, the mechanical loss of the motor is reduced and the efficiency is improved.

[0022] (5) Through optimized shaft design and manufacturing process control, the vibration of the main pump motor rotor and bearing housing is effectively reduced.

[0023] (6) It adopts an integrated base with a four-corner support frame structure. The shape is an unequal octagon, with high assembly precision and good load envelope.

[0024] (7) Dynamic and static coupling isolation measures are adopted at the air inlet of the upper bearing assembly, the lower guide bearing and the motor body (frame). The relative structure of the upper and lower baffles and the upper and lower balance discs plays an isolation role, avoiding the risk of negative pressure and oil leakage of the bearing air seal.

[0025] (8) Compared with similar products at home and abroad, its key technical indicators such as efficiency and vibration are significantly better than those of similar products at home and have reached the level of advanced international products. Attached Figure Description

[0026] Figure 1 This is a structural diagram of the main pump motor of the nuclear power unit of the present invention; Figure 2 This is a structural diagram of the bidirectional thrust bearing of the main pump motor of the nuclear power unit according to the present invention. Detailed Implementation

[0027] To enable those skilled in the art to better understand the technical solution of the present invention, its specific embodiments are described in detail below with reference to the accompanying drawings: Please see Figure 1 and Figure 2 According to an embodiment of the present invention, a main pump motor for a nuclear power unit includes a frame 1, a stator 2, a rotor 3, a base 4, a terminal box 5, an air-water cooler 6, an upper bearing assembly 7, a lower guide bearing 8, and a backflow preventer 9.

[0028] The base 1 is an integral welded structure, employing a four-corner support frame structure with an unequal-sided octagonal horizontal cross-section. The base 1 is welded together from four machine walls 41, four corner support plates 42, the inner wall of the iron core, the upper end cover wall 43, the lower end cover wall 44, the upper wind baffle 11, the lower wind baffle 12, and supporting ribs. The four machine walls 41 are arranged in pairs facing each other, with a corner support plate 42 between each pair of adjacent machine walls 41 (at each corner). The corner support plates 42 are welded to the machine walls 41 to form an unequal-sided octagonal frame structure. Each corner support plate 42 also has a rounded reinforcing rib welded to its inner side, forming a stable structure with the machine walls. The inner wall of the stator core is a ring-shaped steel plate located in the middle of the machine base. It is used to fix the stator core and transmit electromagnetic radial force and thermal expansion force. The outer edge of the inner wall of the stator core is welded to the inner side of the unequal-sided octagonal frame structure. The upper end cover 43 and the lower end cover 44 are welded to the upper and lower ends of the unequal-sided octagonal frame structure respectively. The upper end cover 43 and the lower end cover 44 are the mounting flange surfaces of the upper bearing assembly 7 and the base 4, respectively. The upper baffle plate 11 and the lower baffle plate 12 are used to guide the flow of cooling air and form a dynamic and static sealing structure with the rotor balance disc. The baffle plate 11 and the lower baffle plate 12 are installed on the inner side of the machine wall. The types of support ribs include: longitudinal support ribs, arranged vertically along the inner side of the machine wall, connecting the upper end cover and the lower end cover; and circumferential support ribs, arranged in a ring in the horizontal direction on the inner side of the machine wall to enhance the cross-sectional rigidity.

[0029] The base 4 is welded together from the upper and lower walls, the middle side wall, and the supporting ribs. The upper wall of the base 4 is connected to the lower end cover wall of the base 1.

[0030] The stator 2 is installed inside the base 1; the base 4 is installed at the lower end of the base 1 (lower end cover wall); the outlet box 5 and the air-water cooler 6 are respectively installed on the outside of the base 1; the upper bearing assembly 7 is installed at the upper end of the base 1, which is an integrated assembly of a bidirectional thrust bearing and an upper guide bearing, used to bear the bidirectional axial load and the radial load of the non-shaft extension end of the rotor; the lower guide bearing 8 is installed at the lower end of the base 1 and is located inside the base 4, used to bear the radial load of the shaft extension end of the rotor; the rotor 3 is set inside the stator 2, and the rotor 3 includes a rotating shaft 31 and, from top to bottom, a top balance disc 15, an upper balance disc 16, a rotor core 13, a lower balance disc 17, and a flywheel 14, which are sequentially sleeved on the rotating shaft; the flywheel 14 is set below the rotor core 13 and above the lower guide bearing 8, that is, the flywheel 14 is placed at the bottom and is located between the upper guide bearing and the lower guide bearing 8, which effectively lowers the center of gravity of the motor, reduces the overall vibration of the motor, and makes the shaft vibration stability good, reducing shaft vibration. The upper balance disc 16 and the lower balance disc 17 are located on both sides of the rotor core 13.

[0031] The upper and lower parts of rotor 3 are supported one-to-one by upper bearing assembly 7 and lower guide bearing 8; anti-reverse device 9 is installed on the top of base 1 and located below top balance disc 15. The inner ring of anti-reverse device 9 is connected to shaft 31 (rotating part of motor) and the outer ring is connected to stationary part of motor. One-way anti-reverse function is achieved by wedge block between inner and outer ring.

[0032] The motor's ventilation system is a symmetrical ventilation system with an air-water cooler 6. Air inlets are located at the upper and lower ends of both sides of the base 1; for example, the upper end of the two side walls of the base 1 has two air inlets, and the lower end has four air inlets, with the upper and lower air inlet areas being the same. The stator and rotor ventilation ducts are not aligned. The upper baffle plate 11 is located at the upper air inlet and below the upper bearing assembly 7; the lower baffle plate 12 is located at the lower air inlet and above the flywheel 14. Each bearing and its corresponding air inlet employs dynamic and static coupling isolation measures. The relative structure of the upper baffle plate 11, lower baffle plate 12, and the balance discs (upper balance disc 16 and lower balance disc 17) on both sides of the rotor core provides isolation, preventing the bearing gas seal from bearing negative pressure and the risk of oil leakage. The upper bearing assembly 7 is isolated by the upper baffle plate 11 and upper balance disc 16, and the lower guide bearing 8 is isolated by the lower baffle plate 12 and lower balance disc 17.

[0033] Stator 2 consists of a stator core and stator windings. The stator core is made of fan-shaped silicon steel sheets stacked together, with external pressing and lamination. Stator clamping rings are located at both ends for fixation. Twelve channel steels are evenly distributed and welded to the outer circumference of the stator core, with ventilation openings on the channel steels. The stator windings consist of three independent winding groups, each of which is composed of several coils connected together. The coils are made of copper wires with a surface-insulated material. The stator windings use a low-adhesion insulation system, exhibiting excellent electrical, mechanical, heat resistance, environmental resistance, and radiation resistance.

[0034] The rotor 3's shaft 31 is a welded shaft structure. The rotor core 13 is made of stacked, solid round silicon steel sheets, with rotor pressure rings at both ends for fixation. The rotor guide bars are embedded in the rotor core slots and welded to the end rings, which are then fitted with protective rings. Two centrifugal fans are also mounted on the shaft, located at opposite ends of the rotor core 13. The flywheel is designed to be non-detachable, consisting of a flywheel body and a bushing. The flywheel body is interference-fitted to the shaft via the bushing. The flywheel uses a one-piece forged hot-fit connection without keyways, avoiding stress concentration. A pressure relief structure design ensures adjustable interference fit with the shaft, facilitating easy assembly and disassembly.

[0035] The upper bearing assembly 7 includes a thrust head 21, a bearing housing 22, an upper guide pad 23, an upper thrust pad 24, a lower thrust pad 25, and a cooling pipe 26. The thrust head 21, bearing housing 22, upper thrust pad 24, and lower thrust pad 25 form the core structure of the bidirectional thrust bearing, while the thrust head 21, bearing housing 22, and upper guide pad 23 form the core structure of the upper guide bearing. The thrust head 21 is mounted on the rotating shaft 31 via a heat-shrink fitting. The upper thrust pad 24 and lower thrust pad 25 are respectively located on the upper and lower sides of the lower part of the thrust head 21. When the axial thrust is low, the lower thrust pad 25 bears the load, and when the axial thrust is high, the upper thrust pad 24 bears the load. The upper guide pad 23 is installed inside the bearing housing 22 and located outside the thrust head 21. The cooling pipe 26 is located outside the bearing housing 22.

[0036] A top-mounted thrust bearing design is adopted. Unlike the four-bearing main pump structure, which has two bearings on the main pump side (one of which is a thrust bearing to bear the axial water thrust load), the three-bearing main pump structure only has one guide bearing on the main pump side. Therefore, the motor needs to use a bidirectional thrust bearing, while the main pump motor adapted to the four-bearing main pump structure only needs to use a unidirectional thrust bearing. The non-shaft extension end (upper end) of this motor is equipped with an upper bearing assembly 7, consisting of a bidirectional thrust bearing and an upper guide bearing, to bear the bidirectional axial load and the radial load of the non-shaft extension end of the main pump unit rotor shaft system under various operating conditions. The shaft extension end (lower end) of the motor is equipped with a lower guide bearing 8 to bear the radial load of the shaft extension end of the main pump unit rotor shaft system under various operating conditions.

[0037] The main pump motor of the nuclear power unit of the present invention changes the rated power and other operating parameters of the motor according to different operating conditions, load requirements and environmental requirements of the main pump unit. This causes changes in the external geometric data such as the height and cross-sectional size of the main pump motor, electromagnetic parameters such as the lamination size and core length, design and process parameters such as the thickness of the base steel plate and the number and size of the reinforcing ribs, and ventilation and cooling parameters such as the cooler power, stator and rotor air duct settings and ventilation opening size.

[0038] In summary, the main pump motor of the nuclear power unit of this invention improves maintenance accessibility by placing the thrust bearing on top, lowers the motor's center of gravity and overall vibration by placing the flywheel below and between the two bearings, and improves assembly precision and load envelope through an integrated base. This meets the requirements of nuclear power plants for high reliability, long lifespan, and easy maintenance of the main pump motor. The key technical indicators of this invention, such as efficiency and vibration, are superior to similar domestic products and reach international advanced levels. It is suitable for the main pump motor of third-generation pressurized water reactor nuclear power plants such as the "Hualong One". It can solve the problems of difficult thrust bearing maintenance, poor vibration stability, and low base assembly precision in existing technologies, meeting the requirements of nuclear power plants for high reliability, long lifespan, and easy maintenance of the main pump motor. It boasts excellent performance and is safe and reliable.

[0039] Those skilled in the art should recognize that the above embodiments are merely illustrative of the present invention and are not intended to limit the present invention. Any variations or modifications to the above embodiments that are within the spirit and essence of the present invention will fall within the scope of the claims of the present invention.

Claims

1. A main pump motor for a nuclear power unit, characterized in that, Includes a frame, stator, rotor, base, terminal box, air-water cooler, upper bearing assembly, lower guide bearing, and anti-reverse device, wherein: The base is an integral welded structure with a four-corner support frame structure and its horizontal cross-section is an unequal-sided octagon. The stator is installed inside the frame; The base is installed at the lower end of the machine base; The outlet box and the air-water cooler are respectively installed on the outside of the base; The upper bearing assembly is installed on the upper end of the machine base and is an integrated assembly of a bidirectional thrust bearing and an upper guide bearing, used to bear the bidirectional axial load and the radial load of the non-shaft extension end of the rotor. The lower guide bearing is installed at the lower end of the machine base and is located inside the base to bear the radial load of the rotor shaft extension end; The rotor is disposed inside the stator. The rotor includes a rotating shaft and, from top to bottom, a top balance disc, an upper balance disc, a rotor core, a lower balance disc, and a flywheel, which are sequentially fitted onto the rotating shaft. The flywheel is disposed below the rotor core and above the lower guide bearing. The upper and lower parts of the rotor are supported one-to-one by the upper bearing assembly and the lower guide bearing; The anti-reverse device is installed on the top of the base and is located below the top balance disc.

2. The main pump motor of a nuclear power unit according to claim 1, characterized in that, The upper bearing assembly includes a thrust head, a bearing housing, an upper guide bearing, an upper thrust bearing, a lower thrust bearing, and cooling pipes; wherein: The thrust head, bearing housing, upper thrust pad, and lower thrust pad constitute the core structure of the bidirectional thrust bearing, and the thrust head, bearing housing, and upper guide pad constitute the core structure of the upper guide bearing. The thrust head is mounted on the rotating shaft via a heat-shrinkable sleeve. The upper thrust pad and the lower thrust pad are respectively disposed on the upper and lower sides of the lower part of the thrust head. When the axial thrust is low, the lower thrust pad bears the load, and when the axial thrust is high, the upper thrust pad bears the load. The upper guide plate is installed inside the bearing housing and is located outside the thrust head; The cooling pipes are located outside the bearing housing.

3. The main pump motor of a nuclear power unit according to claim 1, characterized in that, The flywheel is an integral forged structure, connected to the shaft by an interference fit through a bushing, without a keyway, and equipped with a pressure relief structure to achieve adjustable interference; the flywheel adopts a non-detachable design.

4. The main pump motor of a nuclear power unit according to claim 1, characterized in that, The stator consists of a stator core and stator windings. The stator core is made of fan-shaped silicon steel sheets stacked together, with external pressing and lamination. Stator pressure rings are provided at both ends for fixation. Twelve channel steels are evenly distributed and welded on the outer circumference of the stator core, and each channel steel has a ventilation opening. The stator windings consist of three independent winding groups, and each winding group is composed of several coils connected together. The coils are made of copper wires with a surface covered with insulating material. The stator windings adopt a low-adhesion insulation system and have radiation resistance.

5. The main pump motor of a nuclear power unit according to claim 1, characterized in that, The main pump motor adopts a symmetrical ventilation system; air inlets are respectively provided at the upper and lower ends of both sides of the machine base, and the upper and lower air inlet areas are the same; the ventilation channels of the stator and rotor are not aligned.

6. The main pump motor of a nuclear power unit according to claim 5, characterized in that, It also includes an upper wind deflector and a lower wind deflector. The upper wind deflector is located at the upper air inlet and below the upper bearing assembly. The lower wind deflector is located at the lower air inlet and above the flywheel. Each bearing and air inlet adopts dynamic and static coupling isolation measures. The relative structure of the upper and lower wind deflectors with the upper and lower balance discs plays an isolation role, avoiding the risk of negative pressure and oil leakage on the bearing air seal.

7. The main pump motor of a nuclear power unit according to claim 1, characterized in that, The inner ring of the anti-reverse device is connected to the rotating shaft, and the outer ring is connected to the stationary part of the motor. The one-way anti-reverse function is achieved by the wedge between the inner and outer rings.

8. The main pump motor of a nuclear power unit according to claim 1, characterized in that, The rotor shaft is a welded bar shaft structure; the rotor core is made of stacked whole round silicon steel sheets, and rotor pressure rings are provided at both ends for fixation.

9. The main pump motor of a nuclear power unit according to claim 1, characterized in that, Two centrifugal fans are also installed on the rotating shaft, and the two centrifugal fans are located at both ends of the rotor core.

10. The main pump motor of a nuclear power unit according to claim 1, characterized in that, The base is welded together from the upper and lower walls, the middle side wall, and the supporting ribs.

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