Low-speed permanent magnet motor with axial-radial multi-layer pressurization surrounding outer air duct type ventilation cooling system

Abstract

The invention discloses a low-speed permanent magnet motor with an axial-radial multi-layer pressurization surrounding outer air duct type ventilation cooling system, and relates to the field of motors. In order to solve the problem that an existing low-speed permanent magnet motor component is high in temperature, a knife-shaped supercharged centrifugal fan is installed on the upper end face of a rotor, a double-supercharged multi-stage axial flow fan is installed at the lower end of the rotor, a high-coercivity permanent magnet is located in the middle of a trapezoidal permanent magnet, and low-coercivity permanent magnets are located on the two sides of the high-coercivity permanent magnet. M rotor axial ventilation holes are formed in each rotor core, z air guide type U-shaped grooves are formed in the outer surface of each rotor core, an air pressure enhancement type air guide plate is installed in each air guide type U-shaped groove, a stator parallel ventilation channel is formed in the stator core, a surrounding type air channel and a surrounding type water channel are formed in the machine shell, and the surrounding type air channel and the surrounding type water channel are communicated through the air pressure enhancement type air guide plate. A surrounding type air duct inlet and a surrounding type air duct outlet are formed in the machine shell. The power density and the cooling effect of the low-speed permanent magnet motor are improved.

Description

Technical Field

[0001] This invention relates to a low-speed permanent magnet motor with an axial-radial multi-layer pressurized surrounding external air duct ventilation and cooling system, belonging to the field of motors. Background Technology

[0002] Low-speed permanent magnet motors, due to their high magnetic energy density and good stability, have extremely broad application prospects in industrial production, oil field extraction, wind power generation, port lifting, and ship propulsion. Currently, although there are many types and quantities of low-speed permanent magnet motors, existing models still have certain problems, including high energy consumption, excessively high temperatures in some components, failure to meet equipment lifespan performance requirements, and a high failure rate. The internal temperature field of a low-speed permanent magnet motor is an important standard for judging the motor's overall performance and affects its operating efficiency. When the temperature rise inside a low-speed permanent magnet motor is too high, demagnetization of the permanent magnets can easily occur, reducing the motor's lifespan, wasting materials, and increasing operating costs.

[0003] To improve the power density of low-speed permanent magnet motors (PMMs), accelerate the circulation of the entire ventilation and cooling system, enhance the utilization rate of cooling gas, and improve the safe and stable operation of the motor, trapezoidal permanent magnets are installed in the rotor slots. This increases the magnetic field strength within the motor, reduces eddy current losses, lowers the cost of the permanent magnets, improves the magnetic field distribution, and ultimately increases the power density. The novel ventilation and cooling system utilizes a blade-type booster centrifugal fan and a dual-boost multi-stage axial fan to increase the flow rate of cooling gas within the motor. This increases the contact area between the stator and rotor cores and the cooling gas, accelerating the fluid velocity around the stator core, stator windings, permanent magnets, rotor core, and end components. This effectively reduces the temperature of these components, decreasing axial temperature differences and thermal stress, increasing the flow rate of cooling gas within the motor, and lowering its operating costs. Summary of the Invention

[0004] The purpose of this invention is to provide a low-speed permanent magnet motor with an axial-radial multi-layer pressurized surrounding external air duct ventilation and cooling system. This system solves the problem of excessively high temperatures in the stator core, stator windings, rotor core, permanent magnets, and end components caused by unreasonable ventilation design in the stator and rotor regions of traditional low-speed permanent magnet motors. It significantly improves the power density of the low-speed permanent magnet motor, accelerates the circulation of the entire ventilation and cooling system, improves the utilization rate of cooling gas, effectively removes heat from various components and reduces the axial temperature difference of the low-speed permanent magnet motor, resulting in higher efficiency and improved safe and stable operation.

[0005] The present invention relates to a low-speed permanent magnet motor with an axial-radial multi-layer pressurized surrounding external air duct ventilation and cooling system. It includes an upper baffle plate, a blade-shaped pressurized centrifugal fan, an upper air inlet, a surrounding air duct inlet, a surrounding water duct inlet, a surrounding air duct, a surrounding water duct, a stator core, stator interlayer insulation, an air gap, a surrounding air duct outlet, a stator winding, a dual-pressurized multi-stage axial flow fan, a housing, rotor axial ventilation holes, stator slot wedges, a rotor core, a support plate, a stator parallel ventilation duct, a shaft, a surrounding water duct outlet, a lower air outlet, a trapezoidal permanent magnet, a guide U-shaped groove, a pressure-enhanced guide plate, a parallel air duct, and a support body. The dual-pressurized multi-stage axial flow fan consists of an upper dual-pressurized multi-stage axial flow fan and a lower dual-pressurized multi-stage axial flow fan. The trapezoidal permanent magnet consists of a high-coercivity permanent magnet and a low-coercivity permanent magnet. A blade-shaped booster centrifugal fan is installed on the upper end face of the rotor, and a dual-boost multi-stage axial flow fan is installed at the lower end of the rotor. A high-coercivity permanent magnet is located in the middle of the trapezoidal permanent magnet, and a low-coercivity permanent magnet is located on both sides of the high-coercivity permanent magnet. Each rotor core has m rotor axial ventilation holes, and each rotor core has z air-guiding U-shaped grooves on its outer surface. Each air-guiding U-shaped groove has a pressure-enhancing air guide plate installed inside. A stator parallel ventilation channel is provided on the stator core. A surrounding air channel and a surrounding water channel are provided inside the casing. A surrounding air channel inlet and a surrounding air channel outlet are provided inside the casing.

[0006] The rotor has a blade-shaped booster centrifugal fan with a length of 300mm to 450mm mounted on its upper end face; a dual-boost multi-stage axial flow fan with a height of 400mm to 500mm mounted on its lower end; each rotor core has 1 to 3 axial ventilation holes (m); each rotor core has 1 to 3 U-shaped guide slots (z) on its outer surface; a stator parallel ventilation channel with a diameter of 10mm to 30mm is provided on the stator core; the surrounding air duct has a width of 40mm to 80mm; the surrounding water channel has a width of 40mm to 80mm; and the cooling water inlet velocity of the surrounding water channel is 1m / s to 3m / s.

[0007] Preferably, the cross-section of the rotor core surface with the air-guiding U-shaped groove changes from U-shaped to semi-circular, which improves the surface heat dissipation coefficient of the rotor core and further reduces the temperature of the rotor core.

[0008] Preferably, the cross-section of the surrounding water channel inside the casing is changed from rectangular to circular, which increases the heat dissipation coefficient of the stator core surface and further accelerates the water flow rate under the action of gravity, thereby improving the water utilization rate.

[0009] Preferably, the internal air duct of the housing is changed from a surrounding air duct to a parallel air duct, and a support is added to the inner wall of the housing. This increases the flow rate of cooling gas in the low-speed permanent magnet motor, improves the flow speed and utilization rate of the cooling gas, and enhances the ability of the low-speed permanent magnet motor to operate safely and stably.

[0010] Advantages of this invention: Traditional low-speed permanent magnet motors suffer from low internal fluid flow and high component temperature. Compared with traditional low-speed permanent magnet motors, this invention transforms the traditional circumferentially excited solid rectangular permanent magnet into a circumferentially excited three-layer trapezoidal permanent magnet. A blade-shaped booster centrifugal fan is added to the upper end face of the rotor of the traditional low-speed permanent magnet motor, and a dual-boost multi-stage axial flow fan is added to the lower end of the rotor. m rotor axial ventilation holes are opened in each rotor core. A new air-guiding U-shaped groove is opened on the outer surface of each rotor core, and a pressure-enhanced air guide plate is added in each air-guiding U-shaped groove. A new stator parallel ventilation channel is opened on the original solid stator core, and a new surrounding air channel and surrounding water channel are opened inside the original solid casing. Thus, a low-speed permanent magnet motor with an axial-radial multi-layer booster surrounding external air channel ventilation and cooling system is formed. The low-speed permanent magnet motor with a axial-radial multi-layer pressurized surrounding external air duct ventilation and cooling system features a circumferentially excited three-layer trapezoidal permanent magnet, which effectively enhances the magnetic field of the circumferentially excited permanent magnet, reduces the cost of permanent magnets, and increases the power density of the permanent magnet motor. Regarding ventilation and cooling, the addition of a blade-shaped pressurized fan on the upper surface of the rotor further accelerates the flow rate of cooling gas, increasing the airflow within the motor. The addition of a dual-pressurized multi-stage axial flow fan at the lower end of the rotor effectively increases the overall airflow and velocity of the cooling gas, improving its utilization rate. Each rotor core has m axial ventilation holes, reducing its temperature. Because these holes are close to the trapezoidal permanent magnets, they also lower the magnets' temperature, preventing demagnetization. Newly created air-guiding U-shaped grooves on the outer surface of each rotor core increase the contact area between the cooling gas and the core, improving the heat dissipation coefficient of the rotor's outer surface. Each U-shaped air-guiding slot is further equipped with a pressure-enhanced air guide plate. After passing through the air-enhanced air guide plate, the flow rate and pressure of the cooling gas are further increased, effectively removing heat from the stator and rotor cores. Parallel stator ventilation channels have been newly opened on the original solid stator core, effectively removing heat from the stator core and stator windings, solving the problem of excessively rapid temperature rise of the solid stator core in traditional permanent magnet motors. Newly opened surround air ducts and surround water channels inside the original solid casing effectively reduce the temperature of the stator core, increase the power density of the low-speed permanent magnet motor, and thus improve its efficiency. The low-speed permanent magnet motor with an axial-radial multi-layer pressurized surrounding external air duct ventilation and cooling system described in this invention can effectively improve the power density of the low-speed permanent magnet motor, increase the pressure, flow rate and velocity of the cooling gas inside the low-speed permanent magnet motor, improve the utilization rate of the cooling gas, reduce the operating cost of the low-speed permanent magnet motor, and enhance the ability of the low-speed permanent magnet motor to operate safely and stably. Attached Figure Description

[0011] For ease of explanation, the present invention will be described in detail below with reference to specific embodiments and accompanying drawings.

[0012] Figure 1 This is a fluid flow diagram inside a low-speed permanent magnet motor with an axial-radial multi-layer pressurized surrounding external air duct ventilation and cooling system as described in this invention. Figure 2 This is an axial cross-sectional view of the low-speed permanent magnet motor with an axial-radial multi-layer pressurized surrounding external air duct ventilation and cooling system as described in this invention. Figure 3 This is a radial cross-sectional view of the low-speed permanent magnet motor with an axial-radial multi-layer pressurized surrounding external air duct ventilation and cooling system as described in this invention. Figure 4 This is a partial enlarged view of the rotor region of the low-speed permanent magnet motor with an axial-radial multi-layer pressurized surrounding external air duct ventilation and cooling system as described in this invention. Figure 5 This is a top view of the upper dual-pressure multi-stage axial flow fan of the low-speed permanent magnet motor with an axial-radial multi-layer pressurized surrounding external air duct ventilation and cooling system as described in this invention. Figure 6 This is a top view of the blade-shaped pressurized centrifugal fan of the low-speed permanent magnet motor with an axial-radial multi-layer pressurized surrounding external air duct ventilation and cooling system as described in this invention. Figure 7 This is a radial cross-sectional view of the low-speed permanent magnet motor with an axial-radial multi-layer pressurized surrounding external air duct ventilation and cooling system as described in Embodiment 2 of the present invention. Figure 8 This is an axial cross-sectional view of the low-speed permanent magnet motor with an axial-radial multi-layer pressurized surrounding external air duct ventilation and cooling system as described in Embodiment 3 of the present invention. Figure 9 This is an axial cross-sectional view of the low-speed permanent magnet motor with an axial-radial multi-layer pressurized surrounding external air duct ventilation and cooling system as described in Embodiment 4 of the present invention. Figure 10 This is a radial cross-sectional view of the low-speed permanent magnet motor with an axial-radial multi-layer pressurized surrounding external air duct ventilation and cooling system as described in Embodiment 4 of the present invention. In the diagram: 1-Upper baffle plate, 2-Knife-shaped pressurized centrifugal fan, 3-Upper air inlet, 4-Circular air duct inlet, 5-Circular water duct inlet, 6-Circular air duct, 7-Circular water duct, 8-Stator core, 9-Stator interlayer insulation, 10-Air gap, 11-Circular air duct outlet, 12-Stator winding, 13-Dual-pressurized multi-stage axial flow fan, 14-Casing, 15-Rotor axial ventilation hole, 16-Stator slot wedge, 17-Rotor core, 18-Support plate, 19-Stator parallel ventilation duct, 20-Shaft, 21-Circular water duct outlet, 22-Lower air outlet, 23-Trapezoidal permanent magnet, 24-Guided U-shaped groove, 25-Air pressure enhanced air guide plate, 26-Parallel air duct, 27-Support body. The arrows in the figure indicate the flow direction of gas inside a low-speed permanent magnet motor with an axial-radial multi-layer pressurized surrounding external air duct ventilation and cooling system. The and in the figure indicate the inlet and outlet directions of water in the surrounding water channel inside the casing of the low-speed permanent magnet motor with an axial-radial multi-layer pressurized surrounding external air duct ventilation and cooling system. Detailed Implementation

[0013] To make the objectives, technical solutions, and advantages of the present invention clearer, the present invention is described below with reference to specific embodiments shown in the accompanying drawings. However, it should be understood that these descriptions are merely exemplary and not intended to limit the scope of the invention. Furthermore, descriptions of well-known structures and technologies are omitted in the following description to avoid unnecessarily obscuring the concept of the present invention.

[0014] Specific implementation method one: Combining Figure 1 , Figure 2 , Figure 3 , Figure 4 , Figure 5 , Figure 6This embodiment describes a system comprising: an upper baffle plate 1, a blade-shaped booster centrifugal fan 2, an upper air inlet 3, a surrounding air duct inlet 4, a surrounding water duct inlet 5, a surrounding air duct 6, a surrounding water duct 7, a stator core 8, stator interlayer insulation 9, an air gap 10, a surrounding air duct outlet 11, a stator winding 12, a dual-boost multi-stage axial flow fan 13, a housing 14, rotor axial ventilation holes 15, stator slot wedges 16, a rotor core 17, a support plate 18, and a stator flat... The components include a horizontal ventilation duct 19, a rotating shaft 20, a surrounding water outlet 21, a lower air outlet 22, a trapezoidal permanent magnet 23, a guide U-shaped channel 24, a pressure-enhanced air guide plate 25, a parallel air duct 26, a support body 27, a dual-pressure multi-stage axial flow fan 13 consisting of an upper dual-pressure multi-stage axial flow fan 13-1 and a lower dual-pressure multi-stage axial flow fan 13-2, and a trapezoidal permanent magnet 23 consisting of a high coercivity permanent magnet 23-1 and a low coercivity permanent magnet 23-2. A blade-shaped booster centrifugal fan 2 is installed on the upper end face of the rotor, and a dual-boost multi-stage axial flow fan 13 is installed on the lower end of the rotor. A high coercivity permanent magnet 23-1 is located in the middle of the trapezoidal permanent magnet 23, and a low coercivity permanent magnet 23-2 is located on both sides of the high coercivity permanent magnet 23-1. Each rotor core 17 has m rotor axial ventilation holes 15. Each rotor core 17 has z air-guiding U-shaped grooves 24 on its outer surface. Each air-guiding U-shaped groove 24 has a pressure-enhancing air guide plate 25 installed inside. A stator parallel ventilation channel 19 is opened on the stator core 8. A surrounding air channel 6 and a surrounding water channel 7 are opened inside the casing 14. A surrounding air channel inlet 4 and a surrounding air channel outlet 11 are opened inside the casing 14.

[0015] The blade-shaped booster centrifugal fan 2 mounted on the upper end of the rotor has a length of 300mm to 450mm, and is 400mm in this embodiment; the dual-boost multi-stage axial flow fan 13 mounted on the lower end of the rotor has a height of 400mm to 500mm, and is 450mm in this embodiment; the number m of rotor axial ventilation holes 15 opened on each rotor core 17 is 1 to 3, and is 2 in this embodiment; the number z of air-guiding U-shaped grooves 24 opened on the outer surface of each rotor core 17 is... The number of ventilation channels is 1 to 3, and in this embodiment, it is 2; a stator parallel ventilation channel 19 with a diameter of 10mm to 30mm is provided on the stator core 8, and in this embodiment, it is 20mm; the width of the surrounding air channel 6 is 40mm to 80mm, and in this embodiment, it is 60mm; the width of the surrounding water channel 7 is 40mm to 80mm, and in this embodiment, it is 60mm; the flow velocity of the cooling water at the inlet 5 of the surrounding water channel is 1m / s to 3m / s, and in this embodiment, it is 1.2m / s.

[0016] The low-speed permanent magnet motor with a blade-type booster-dual-boost multi-stage axial flow fan, in terms of electromagnetic field, replaces the traditional circumferentially excited solid rectangular permanent magnet with a circumferentially excited three-layer trapezoidal permanent magnet 23. A high-coercivity permanent magnet 23-1 is located in the middle of the trapezoidal permanent magnet 23, and low-coercivity permanent magnets 23-2 are located on both sides of the high-coercivity permanent magnet 23-1. This effectively enhances the magnetic field of the circumferentially excited trapezoidal permanent magnet 23 and reduces the cost of the permanent magnet. Since the bottom of the trapezoidal permanent magnet 23 is far from the air gap between the stator core 8 and the rotor core 17, using a trapezoidal permanent magnet 23 effectively solves the problem of a weak magnetic field at the bottom of the permanent magnet, improves the magnetic field distribution of the permanent magnet, and increases the power density of the low-speed permanent magnet motor. In terms of ventilation and cooling, a blade-shaped booster centrifugal fan 2 is added to the upper end face of the traditional low-speed permanent magnet motor rotor, a dual-boost multi-stage axial flow fan 13 is added to the lower end of the rotor, a new air-guiding U-shaped groove 24 is opened on the outer surface of each rotor core 17, and a pressure-enhancing air guide plate 25 is added in each air-guiding U-shaped groove 24. A new stator parallel ventilation channel 19 is opened on the original solid stator core 8, and a new surrounding air channel 6 and a surrounding water channel 7 are opened inside the original solid casing 14. When the low-speed permanent magnet motor is running at its rated speed, the rotating shaft 20 drives the dual-boost multi-stage axial flow fan 13 to rotate. Under the action of the lower dual-boost multi-stage axial flow fan 13-2, the flow rate and pressure of the cooling gas increase. After the cooling gas reaches the upper dual-boost multi-stage axial flow fan 13-1, the flow rate and pressure of the cooling gas further increase under the action of the upper dual-boost multi-stage axial flow fan 13-1, which enhances the heat dissipation coefficient of the lower stator end winding surface and reduces the temperature of the lower stator end winding. After cooling the lower stator end winding, the cooling gas splits into three streams from the lower stator end winding to the upper stator end winding.The first cooling gas flows axially upward through the stator parallel ventilation channel 19 on the stator core 8, increasing the utilization rate of the cooling gas and the contact area between the cooling gas and the stator core 8. Under the action of the dual-boost multi-stage axial flow fan 13, the flow rate of the cooling gas increases, effectively removing heat from the stator core 8 and stator winding 12, solving the problem of excessively rapid temperature rise of the stator core 8 during operation in traditional low-speed permanent magnet motors. The second cooling gas flows axially upward through the air gap 10 and the air-guided U-shaped groove 24 on the outer surface of the rotor core 17. After passing through the air pressure-enhancing air guide plate 25 installed within the air-guided U-shaped groove 24, the flow rate and pressure of the cooling gas further increase, while the high pressure and... A large flow of cooling gas flows axially within the air gap 10 between the stator core 8 and the rotor core 17, effectively removing heat from both and reducing their temperatures. A third stream of cooling gas flows upwards along the rotor axial ventilation holes 15 on the rotor core 17. The increased flow rate of the cooling gas, facilitated by the dual-boost multi-stage axial fan 13 installed at the lower end of the rotor, further removes heat from the rotor core 17. Since the rotor axial ventilation holes 15 are close to the trapezoidal permanent magnet 23, they further remove heat from the trapezoidal permanent magnet 23, effectively reducing the temperature of both the rotor core 17 and the trapezoidal permanent magnet 23 and extending its service life. The three cooling gases reach the upper stator end winding, carrying away the heat. After lowering the temperature of the upper stator end winding, the second and third cooling gases reach the blade-type booster centrifugal fan 2 installed on the upper end face of the rotor. The fan 2 rotates via the shaft 20, increasing the flow rate of the second and third cooling gases. This accelerates the flow of the cooling gases through the upper stator end winding. After being guided by the upper baffle plate 1, the cooling gases merge with the first cooling gas and flow together into the upper air inlet 3, reaching the interior of the casing 14. The surrounding air duct inlet 4 enters the surrounding air duct 6 inside the housing 14. The cooling gas flows from top to bottom along the surrounding air duct 6 inside the housing 14, increasing the flow rate of the cooling gas inside the low-speed permanent magnet motor, improving the utilization rate of the cooling gas, and reducing the axial temperature of the stator core 8. After passing through the surrounding air duct 6, the cooling gas flows out from the surrounding air duct outlet 11, passes through the lower air outlet 22, and reaches the dual-boost multi-stage axial flow fan 13 at the lower end of the rotor again, completing the circulation of the entire cooling gas inside the low-speed permanent magnet motor with an axial-radial multi-layer booster surrounding external air duct ventilation and cooling system.A surrounding water channel 7 is formed inside the casing 14. Water flows through the surrounding water channel inlet 5, through the surrounding water channel 7, and to the surrounding water channel outlet 21. This effectively removes heat from the stator core 8, increases the heat dissipation coefficient of the stator core 8 surface, and reduces the temperature of the stator core 8. Since the surrounding water channel 7 is close to the surrounding air duct 6, the coolant can remove some of the heat from the cooling gas in the surrounding air duct 6. Furthermore, the flow rate of the coolant can be further increased under the action of gravity, improving the utilization rate of the coolant. This effectively increases the power density of the low-speed permanent magnet motor, making the low-speed permanent magnet motor more efficient.

[0017] Specific Implementation Method Two: Combining Figure 7 This embodiment differs from Embodiment 1 in that the cross-section of the air-guiding U-shaped groove 24 on the surface of the rotor core 17 is changed from U-shaped to semi-circular, which improves the surface heat dissipation coefficient of the rotor core 17 and further reduces the temperature of the rotor core 17. Other components and connections are the same as in Embodiment 1.

[0018] Specific implementation method three: Combining Figure 8 This embodiment differs from Embodiment 1 in that the cross-section of the encircling water channel 7 inside the housing 14 is changed from rectangular to circular, increasing the heat dissipation coefficient of the stator core 8 surface. Under gravity, the water flow rate can be further accelerated, improving water utilization. Other components and connections are the same as in Embodiment 1.

[0019] Specific implementation method four: Combination Figure 9 and Figure 10 This embodiment differs from Embodiment 1 in that the internal air duct 6 of the housing 14 is replaced with a parallel air duct 26, and a support 27 is added to the inner wall of the housing 14. This increases the flow rate of cooling gas inside the low-speed permanent magnet motor, improves the flow speed and utilization rate of the cooling gas, and enhances the ability of the low-speed permanent magnet motor to operate safely and stably. Other components and connections are the same as in Embodiment 1.

[0020] The foregoing has shown and described the basic principles, main features, and advantages of the present invention. Those skilled in the art should understand that the present invention is not limited to the above embodiments. The embodiments and descriptions in the specification are merely illustrative of the principles of the invention. Various changes and modifications can be made to the invention without departing from its spirit and scope, and all such changes and modifications fall within the scope of the present invention as claimed. The scope of protection of this invention is defined by the appended claims and their equivalents.

Claims

1. A low speed permanent magnet electric machine with axial-radial multi-layer plenum-encircled outer duct type ventilation cooling system, characterized in that: It includes an upper baffle plate (1), a blade-shaped booster centrifugal fan (2), an upper air inlet (3), a surrounding air duct inlet (4), a surrounding water duct inlet (5), a surrounding air duct (6), a surrounding water duct (7), a stator core (8), stator interlayer insulation (9), an air gap (10), a surrounding air duct outlet (11), a stator winding (12), a dual-boost multi-stage axial flow fan (13), a casing (14), rotor axial ventilation holes (15), and stator slot wedges (16).

17. Rotor core (18), support plate (19), stator parallel ventilation duct (10), rotating shaft (21), surrounding water channel outlet (22), lower air outlet (23), trapezoidal permanent magnet (24), air guide U-shaped groove (25), air pressure enhanced air guide plate (26), parallel air duct (27), support body (28), dual-pressure multi-stage axial flow fan (13) consisting of upper dual-pressure multi-stage axial flow fan (13-1) and lower dual-pressure multi-stage axial flow fan (13-2) The trapezoidal permanent magnet (23) is composed of a high coercivity permanent magnet (23-1) and a low coercivity permanent magnet (23-2). A blade-shaped booster centrifugal fan (2) is installed on the upper end face of the rotor, and a dual-boost multi-stage axial flow fan (13) is installed on the lower end of the rotor. The high coercivity permanent magnet (23-1) is located in the middle of the trapezoidal permanent magnet (23), and the low coercivity permanent magnet (23-2) is located on both sides of the high coercivity permanent magnet (23-1). Each rotor core (17) has an m A rotor axial ventilation hole (15) is provided, and z air-guiding U-shaped grooves (24) are provided on the outer surface of each rotor core (17). A pressure-enhanced air guide plate (25) is installed in each air-guiding U-shaped groove (24). A stator parallel ventilation channel (19) is provided on the stator core (8). A surrounding air channel (6) and a surrounding water channel (7) are provided inside the casing (14). A surrounding air channel inlet (4) and a surrounding air channel outlet (11) are provided inside the casing (14).

2. The low speed permanent magnet motor with shaft-radial multi-layer plenum-encircled outer-duct type ventilation cooling system of claim 1, wherein: The upper end of the rotor is equipped with a blade-shaped booster centrifugal fan (2) with a length of 300mm to 450mm; the lower end of the rotor is equipped with a double booster multi-stage axial flow fan (13) with a height of 400mm to 500mm; each rotor core (17) has 1 to 3 rotor axial ventilation holes (15); each rotor core (17) has 1 to 3 air-guiding U-shaped grooves (24) on its outer surface; a stator parallel ventilation channel (19) with a diameter of 10mm to 30mm is provided on the stator core (8); the width of the surrounding air duct (6) is 40mm to 80mm; the width of the surrounding water channel (7) is 40mm to 80mm; the flow rate of the cooling water at the inlet (5) of the surrounding water channel is 1m / s to 3m / s.

3. The low speed permanent magnet motor with shaft-radial multi-layer plenum-encircled outer-duct type ventilation cooling system of claim 1, wherein: The rotor core (17) has a U-shaped groove (24) on its surface, and the cross-section changes from U-shaped to semi-circular.

4. The low-speed permanent magnet motor with an axial-radial multi-layer pressurized surrounding external air duct ventilation and cooling system according to claim 1, characterized in that: The cross-section of the encircling waterway (7) inside the casing (14) changes from rectangular to circular.

5. The low-speed permanent magnet motor with an axial-radial multi-layer pressurized surrounding external air duct ventilation and cooling system according to claim 1, characterized in that: The parallel air duct (26) is arranged in the ring air duct (6) in the shell (14), and the support body (27) is additionally arranged on the inner wall of the shell (14).

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