Permanent magnet direct drive motor stator cooling system

Abstract

This invention discloses a stator cooling system for a permanent magnet direct drive motor, belonging to the field of motor cooling technology. The system includes: a working condition acquisition module for acquiring real-time operating condition data of the permanent magnet direct drive motor; a heat generation mapping module for determining the distribution of heat-generating areas in the stator windings of the permanent magnet direct drive motor during the current operating cycle based on the real-time operating condition data; a cavity construction module for constructing multi-layer gradient cooling cavities on the inner wall of the stator housing of the permanent magnet direct drive motor according to the distribution of heat-generating areas in the stator windings, with the multi-layer gradient cooling cavities segmented along the axial direction of the stator housing; a flow guiding arrangement module for arranging cross-flow guiding heat exchange units in the multi-layer gradient cooling cavities, with the cross-flow guiding heat exchange units connected to the cooling medium circulation loop outside the stator housing; and a circulating heat dissipation module for performing layered cascade heat exchange on the heat-generating areas of the stator windings through the cross-flow guiding heat exchange units, and guiding the high-temperature cooling medium after heat exchange to the cooling medium circulation loop for heat dissipation.

Description

Technical Field

[0001] This invention relates to the field of motor cooling technology, specifically to a stator cooling system for a permanent magnet direct drive motor. Background Technology

[0002] During operation, permanent magnet direct drive motors generate Joule heat due to resistive losses in the stator windings caused by current flow. Because of the uneven distribution of the electromagnetic field within the motor and differences in heat dissipation conditions, the stator windings exhibit non-uniform heat distribution along the axial and circumferential directions. Existing stator cooling methods often employ axial or spiral cooling channels of uniform depth and structure within the housing, injecting a low-temperature cooling medium from one end, allowing it to flow through the entire stator, and then exiting from the other end. This uniform cooling structure design cannot match the actual regional differences in heat intensity within the stator windings, resulting in insufficient heat dissipation in high-temperature areas and over-cooling in low-temperature areas, leading to a large overall temperature gradient in the stator and difficulty in eliminating localized hot spots.

[0003] The drawback of existing technologies lies in the fact that the geometric parameters of the cooling cavity are fixed and not differentiated according to the actual distribution of the stator winding's heating areas. When the cooling medium flows within a channel of a single cross-sectional shape and size, its velocity boundary layer and thermal boundary layer development patterns are uniform, making it impossible to actively adjust the heat transfer coefficient for regions with different heat flux densities. Simultaneously, as the cooling medium flows over long distances, its temperature gradually increases, and the heat transfer driving force decreases along the flow path, further exacerbating the insufficient cooling capacity in downstream high-temperature regions. This overall uniform cooling strategy essentially fails to establish a spatial mapping relationship between heating and cooling intensity, resulting in the cooling medium's heat transfer potential not being fully exploited. Both the improvement of motor power density and the extension of insulation life are constrained by the thermal bottleneck. To solve these problems, improvements are needed at both the spatial configuration of the cooling cavity and the flow organization of the cooling medium. Summary of the Invention

[0004] The purpose of this invention is to provide a stator cooling system for a permanent magnet direct drive motor. By constructing a multi-layer gradient cooling cavity that matches the distribution of the heating area of ​​the stator winding, and arranging cross-flow heat exchange units inside it, the system achieves refined layered cooling of non-uniform heating areas, reduces the stator temperature gradient, and eliminates local hot spots.

[0005] To achieve the above objectives, the present invention provides the following technical solution: The present invention provides a stator cooling system for a permanent magnet direct drive motor, including an operating condition acquisition module, a heat mapping module, a cavity construction module, a flow guiding arrangement module, and a circulating heat dissipation module. The operating condition acquisition module is used to acquire real-time operating condition data of the permanent magnet direct drive motor, and the heat mapping module determines the distribution of the stator winding heat-generating area of ​​the motor in the current operating cycle based on the real-time operating condition data, thereby achieving accurate perception of the heat generation status and providing a basis for subsequent differentiated cooling.

[0006] As a preferred embodiment of the present invention, in determining the distribution of the heating region of the stator winding, the stator phase current time-series waveform and rotor position angle sequence are extracted from real-time operating data. The stator phase current time-series waveform undergoes fundamental and harmonic component separation processing to obtain the fundamental current amplitude sequence and harmonic current distortion rate sequence. Based on the rotor position angle sequence, the fundamental current amplitude sequence and harmonic current distortion rate sequence are subjected to spatiotemporal synchronous mapping processing to generate a current density distribution map of the stator winding along the circumferential direction. Then, combined with the resistivity temperature coefficient of the stator winding conductor material, the Joule heat generation rate distribution of the stator winding in each spatial partition is calculated, thereby obtaining an accurate distribution of the heating region of the stator winding.

[0007] Preferably, when calculating the Joule heat generation rate distribution, the current density distribution spectrum is mapped onto each conductor strand in each stator slot according to the conductor arrangement in the stator winding slot, obtaining the strand current density value of each conductor strand; the reference Joule heat generation rate is calculated based on the strand current density value and the reference resistivity of the conductor material, and temperature correction is performed according to the temperature difference between the current operating temperature of each conductor strand and the reference temperature and the resistivity temperature coefficient, to obtain the actual Joule heat generation rate of each conductor strand; finally, the actual Joule heat generation rates of all conductor strands in each stator slot are summed to obtain the Joule heat generation rate distribution in each spatial partition, making the heat generation calculation more precise and closer to the actual operating state.

[0008] The cavity construction module constructs a multi-layered gradient cooling cavity on the inner wall of the stator housing of the permanent magnet direct drive motor according to the distribution of the stator winding heating areas. This multi-layered gradient cooling cavity is segmented along the axial direction of the stator housing to match the axial differences in heating intensity. Preferably, when constructing the multi-layered gradient cooling cavity, the heating areas of the stator winding are first divided into heating intensity levels, and the axial section of the stator housing is divided into high-temperature, medium-temperature, and low-temperature sections. A first-depth cooling cavity is formed on the inner wall of the stator housing corresponding to the high-temperature section, a second-depth cooling cavity is formed in the medium-temperature section, and a third-depth cooling cavity is formed in the low-temperature section. The radial depth of the first-depth cooling cavity is greater than the radial depth of the second-depth cooling cavity, and the radial depth of the second-depth cooling cavity is greater than the radial depth of the third-depth cooling cavity, making the cooling cavity depth positively correlated with the heating intensity, thus enhancing the heat dissipation capacity of the high-temperature areas. Meanwhile, a first set of spiral guide ribs is provided on the inner wall of the first depth cooling cavity, a second set of spiral guide ribs is provided on the inner wall of the second depth cooling cavity, and a third set of spiral guide ribs is provided on the inner wall of the third depth cooling cavity. The spiral helix angle of the first set of spiral guide ribs is smaller than that of the second set of spiral guide ribs, and the spiral helix angle of the second set of spiral guide ribs is smaller than that of the third set of spiral guide ribs, thus forming a multi-layer gradient cooling cavity. The spiral guide ribs with different helix angles impart different flow characteristics to the cooling medium, thereby achieving matching with the temperature distribution.

[0009] When classifying the heating intensity level, the highest heating temperature value and the average heating temperature value in the heating area distribution can be calculated. The area with the heating temperature value greater than the product of the highest heating temperature value and the first coefficient is marked as a high temperature candidate area. The area with the heating temperature value between the average heating temperature value and the product of the highest heating temperature value and the first coefficient is marked as a medium temperature candidate area. The area with the heating temperature value less than or equal to the average heating temperature value is marked as a low temperature candidate area. The first coefficient is preferably 0.8. Then, the candidate areas are processed by merging connected components to obtain the starting and ending positions of the high temperature segment, medium temperature segment and low temperature segment in the axial direction of the stator shell, so that the segment division is smoother and more continuous and avoids frequent switching.

[0010] The flow guiding module arranges cross-flow heat exchange units in the multi-layer gradient cooling cavity, and the cross-flow heat exchange units are connected to the cooling medium circulation loop outside the stator shell. Preferably, when arranging the cross-flow heat exchange units, multiple levels of baffle assemblies are arranged sequentially from the cavity inlet to the cavity outlet of the multi-layer gradient cooling cavity, and the multiple levels of baffle assemblies are arranged at equal intervals along the axial direction of the stator shell; a first set of jet holes and a second set of jet holes are respectively opened on the front and back surfaces of each level of baffle assembly, and the diameter of the first set of jet holes is larger than that of the second set of jet holes; an arc-shaped flow guiding pipe is erected between two adjacent levels of baffle assemblies, the inlet end of the arc-shaped flow guiding pipe is connected to the jet collection groove of the previous level of baffle assembly, and the outlet end is connected to the jet distribution groove of the next level of baffle assembly, and the jet distribution groove of each level of baffle assembly is sealed and fixedly connected to the arc-shaped flow guiding pipe to form a cross-flow heat exchange unit. By using multi-stage baffles and differentiated jet orifices, the cooling medium is prompted to repeatedly change its flow direction and form a high-speed jet, which disrupts the thermal boundary layer and significantly improves the convective heat transfer coefficient.

[0011] Further preferably, multiple first jet holes are arranged at a first radial spacing on the front side of each baffle assembly, and the angle between the central axis of each first jet hole and the normal direction of the baffle assembly surface is the first jet deflection angle; multiple second jet holes are arranged at a second radial spacing on the back side, and the angle between the central axis of each second jet hole and the normal direction of the baffle assembly surface is the second jet deflection angle, and the second jet deflection angle is greater than the first jet deflection angle; at the same time, an arc-shaped guide groove is opened in the edge region of the back side, and the bottom of the groove is connected to the jet collection groove. Through different jet deflection angles and guide groove designs, the cooling medium forms cross-jet sprays in different flow directions, enhancing the turbulence and mixing of the fluid.

[0012] When constructing the bow-shaped flow guide pipe, the bow height and bow chord length are determined based on the axial spacing between adjacent baffle assemblies. The first straight section, the bow-shaped curved section, and the second straight section are then arranged according to these dimensions, with the convex direction of the bow-shaped curved section facing the inner wall of the stator housing. The end of the first straight section is inserted and sealed to the outlet of the jet collecting groove of the preceding baffle assembly, and the end of the second straight section is inserted and sealed to the inlet of the jet distributing groove of the following baffle assembly. This bow-shaped pipe structure extends the flow path of the cooling medium within a limited space and further promotes fluid mixing and heat exchange by utilizing the centrifugal force effect generated by the curved section.

[0013] The circulating heat dissipation module performs layered cascaded heat exchange on the stator winding heating area through a cross-flow heat exchange unit, and guides the high-temperature cooling medium after heat exchange to the cooling medium circulation loop for heat dissipation. Preferably, during the layered cascaded heat exchange, the low-temperature cooling medium supplied by the cooling medium circulation loop is simultaneously introduced into the cavity inlet of each axial section of the multi-layer gradient cooling cavity according to a preset initial flow distribution ratio. In the high-temperature zone, when the cooling medium flows through the first set of spiral guide ribs, the first set of spiral guide ribs applies a first tangential velocity component to the cooling medium, causing the cooling medium to form a first spiral turbulence that impacts the stator winding in a radially inward direction within the first depth cooling cavity; in the medium-temperature zone, when the cooling medium flows through the second set of spiral guide ribs, the second set of spiral guide ribs applies a second tangential velocity component to the cooling medium, causing the cooling medium to form a second spiral turbulence that sweeps across the stator winding in a circumferential direction within the second depth cooling cavity; in the low-temperature zone, when the cooling medium flows through the third set of spiral guide ribs, the third set of spiral guide ribs applies a third tangential velocity component to the cooling medium, causing the cooling medium to form a third spiral turbulence that sweeps across the stator winding in an axial direction within the third depth cooling cavity. By creating spiral turbulent flow patterns with different flow directions in different temperature zones, the high-temperature zone achieves highly penetrating radial impact cooling, the medium-temperature zone achieves uniform circumferential sweeping cooling, and the low-temperature zone achieves economical and efficient axial sweeping cooling. This achieves layered cascaded heat exchange, which not only effectively reduces the winding hot spot temperature but also avoids energy waste caused by over-cooling and improves the temperature uniformity of the entire stator.

[0014] More preferably, when radially impacting spiral turbulence is formed in the high-temperature section, the cooling medium flows axially along the first depth cooling cavity. It is tangentially deflected by the first spiral surface of the first set of spiral guide ribs, causing its axial mainstream direction to deflect at a first deflection angle relative to the radial direction of the stator housing. It is then guided to the radial bottom surface of the first depth cooling cavity, where it forms an impact jet pointing towards the stator winding slot bottom insulation layer. After impacting the slot bottom insulation layer, the impact jet guides the cooling medium backflow through the cavity sidewall, allowing the returned cooling medium to re-enter the mainstream channel along the first spiral surface, thus carrying the first tangential velocity component to continuously participate in the circulating heat exchange. This flow structure combining impact and backflow greatly enhances the efficient heat exchange near the slot bottom insulation layer, directly targeting the highest temperature area at the bottom of the slot and effectively suppressing the thermal aging of the insulation material.

[0015] The permanent magnet direct drive motor stator cooling system of the present invention achieves adaptive cooling of the heat distribution of the stator winding through the synergistic effects of operating condition sensing, precise heat mapping, gradient cavity construction, cross-flow arrangement, and layered cascade heat exchange. It reduces the maximum temperature while minimizing the axial and circumferential temperature difference, thereby improving the reliability and efficiency of motor operation.

[0016] The technical effects and advantages provided by the present invention in the above technical solution are as follows: Based on the distribution of the stator winding's heating regions, the cooling cavities on the inner wall of the stator housing are constructed as a multi-layered gradient structure with radial depth varying along the axial direction. The radial depth of the cavities corresponding to the high-temperature regions is the largest, while the radial depth of the cavities corresponding to the low-temperature regions is the smallest. Helical guide fins with different helix angles are configured on the inner walls of cavities at different depths; smaller helix angles are used in the high-temperature regions, and larger helix angles are used in the low-temperature regions. When the cooling medium flows through the deep cavities and small-angle helical guide fins in the high-temperature regions, it experiences significant tangential deflection, forming a helical turbulent flow that impacts the stator winding slot bottom insulation layer radially inward. This impact jet directly disrupts the temperature boundary layer in the slot bottom region, establishing an extremely high local convective heat transfer coefficient on the surface of the insulation layer where heat generation is strongest. Conversely, when flowing through the medium-depth cavities and medium-angle helical guide fins in the medium-temperature regions, the tangential velocity component generated by the cooling medium is moderate, forming a helical turbulent flow that sweeps across the stator winding circumferentially, expanding the circumferential heat transfer coverage while maintaining radial heat transfer penetration depth. When the cooling medium flows through the shallow cavity and large helical angle fins in the low-temperature section, the tangential deflection is small, forming a flow pattern that sweeps across the stator windings axially, maintaining the basic heat dissipation requirements of this region with minimal flow resistance. This structure, which configures the cavity depth and fin helical angle differently according to the heat intensity level, precisely distributes the flow momentum of the cooling medium to areas with concentrated heat load, ensuring that different heat intensity sections receive cooling capacity matching their heat output, avoiding the problems of undercooling in high-temperature areas and overcooling in low-temperature areas under a uniform cooling structure.

[0017] Within the multi-layer gradient cooling chamber, multiple stages of baffle assemblies are arranged at equal intervals along the axial direction. Each stage of the baffle assembly has jet holes of different diameters on its front and back surfaces, and adjacent stages are connected by arc-shaped guide pipes. When the cooling medium passes through the large-diameter jet holes on the front surface, the resulting jet core region exhibits high velocity and strong turbulence, causing intense disturbance to the fluid near the stator wall in front of the baffle. After passing through the baffle, the small-diameter jet holes on the back surface cause the medium to exit with a larger jet deflection angle and higher flow velocity, forming a small-scale high-frequency vortex group downstream, continuously tearing and reorganizing the flow boundary layer in front of the next stage baffle. The curved protrusions of the arc-shaped guide pipes face towards the inner wall of the stator shell, guiding some of the cooling medium to the annular region near the inner wall, enhancing heat absorption near the chamber wall, and then redistributing it to the jet region of the next stage baffle. This combined flow structure of jet impact, bow-shaped flow splitting and vortex disturbance, which repeats axially, causes the cooling medium in the entire cooling chamber to repeatedly undergo boundary layer destruction and reconstruction in the flow direction. This eliminates the stable thick boundary layer that develops along the flow path in conventional direct flow channels, and distributes the heat exchange temperature difference evenly over a longer flow path, significantly improving the heat carrying capacity of the cooling medium per unit volume. Attached Figure Description

[0018] To more clearly illustrate the technical solutions in the embodiments of this application or the prior art, the drawings used in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments recorded in this invention. For those skilled in the art, other drawings can be obtained based on these drawings.

[0019] Figure 1 This is a schematic diagram of the stator cooling system of a permanent magnet direct drive motor; Figure 2 This is a flowchart for obtaining the Joule heat generation rate distribution of the stator winding of a permanent magnet direct drive motor; Figure 3 This is a schematic diagram of the multi-layer gradient cooling cavity structure of the stator housing; Figure 4 This is a schematic diagram of the gradient cooling cavity layered spiral turbulent heat transfer principle; Figure 5 This is a schematic diagram of a multi-layer gradient cooling cavity, its baffle assembly, and its bow-shaped flow guide pipe structure. Detailed Implementation

[0020] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0021] See Figure 1 This invention provides a stator cooling system for a permanent magnet direct drive motor. The system includes an operating condition acquisition module, a heat generation mapping module, a cavity construction module, a flow guiding module, and a circulating heat dissipation module. The operating condition acquisition module acquires real-time operating condition data of the permanent magnet direct drive motor. The heat generation mapping module determines the distribution of the stator winding heat generation area within the current operating cycle based on the real-time operating condition data. The cavity construction module constructs a multi-layer gradient cooling cavity on the inner wall of the stator housing of the permanent magnet direct drive motor according to the distribution of the stator winding heat generation area. The multi-layer gradient cooling cavity is segmented along the axial direction of the stator housing. The flow guiding module arranges cross-flow heat exchange units within the multi-layer gradient cooling cavity, and these cross-flow heat exchange units are connected to the cooling medium circulation loop outside the stator housing. The circulating heat dissipation module performs layered cascade heat exchange on the stator winding heat generation area through the cross-flow heat exchange units and guides the high-temperature cooling medium after heat exchange to the cooling medium circulation loop for heat dissipation. Example 1:

[0022] In specific implementation, please refer to Figure 2 The operating condition acquisition module acquires real-time operating condition data by communicating with the permanent magnet direct drive motor driver or through an independent sensor group. From the real-time operating condition data, it extracts the stator phase current timing waveform and rotor position angle sequence of the permanent magnet direct drive motor. The stator phase current timing waveform is obtained by current sensors synchronously sampling the current of each phase of the stator winding at a fixed sampling frequency. The rotor position angle sequence is composed of the rotor mechanical angle or electrical angle time sequence synchronously acquired by position sensors.

[0023] When separating the fundamental and harmonic components of the stator phase current time-series waveform, a fast Fourier transform can be used to perform time-frequency analysis on the waveform. The amplitude-time variation curve corresponding to the fundamental frequency can be extracted from the spectrum to obtain the fundamental current amplitude sequence. Simultaneously, the amplitudes of each harmonic component can be extracted, and the harmonic current distortion rate sequence can be calculated point-by-point according to the total harmonic distortion rate calculation method. Alternatively, an adaptive notch filter can be used to separate the fundamental and harmonic components in real time, outputting the fundamental current amplitude sequence and the harmonic current distortion rate sequence.

[0024] After obtaining the fundamental current amplitude sequence and harmonic current distortion rate sequence, spatiotemporal synchronization mapping is performed based on the rotor position angle sequence. This spatiotemporal synchronization mapping process, based on the pole pair number and stator winding distribution function of the permanent magnet direct drive motor, maps the fundamental current amplitude and harmonic current distortion rate at each sampling moment to the rotor position angle. Through the winding spatial distribution matrix, the time-dimensional current information is mapped to the current density value in the spatial angular dimension of the stator's inner circumference, generating a current density distribution map of the stator winding along the circumferential direction. This current density distribution map characterizes the current density amplitude formed by the combined action of the fundamental current and harmonic current at various spatial angular positions on the stator circumference.

[0025] After obtaining the current density distribution map, it is mapped according to the conductor arrangement in the stator winding slots. The conductor arrangement in the stator winding slots includes the number of conductor layers per slot, the number of conductor strands per layer, and the spatial coordinates of the strands. The spatial position of the current density distribution map in the circumferential direction is correlated with the center angle of the slot opening of each stator slot. For each stator slot, based on the specific position of each conductor strand in the slot height and width directions, the current density value corresponding to the circumferential angle in the current density distribution map is distributed to each conductor strand through two-dimensional interpolation or projection methods, thus obtaining the strand current density value of each conductor strand.

[0026] The reference Joule heat generation rate for each conductor strand is calculated based on the strand current density and the reference resistivity of the conductor material. The reference resistivity of the conductor material refers to its resistivity at a reference temperature. The reference Joule heat generation rate is given by the following formula:

[0027] in, This indicates the baseline Joule heat generation rate, expressed in watts per cubic meter. This represents the current density of the strand, expressed in amperes per square meter. This represents the reference resistivity of the conductor material at a reference temperature, measured in ohm-meters. The reference temperature is set as the average temperature of the stator windings when the motor is cold and unloaded, typically 25 degrees Celsius or calibrated according to the actual ambient temperature.

[0028] After calculating the reference Joule heat generation rate, a temperature correction process is applied to the reference Joule heat generation rate based on the temperature difference between the current operating temperature of each conductor strand and the reference temperature, combined with the temperature coefficient of resistivity. The temperature correction process follows the linear relationship between conductor resistivity and temperature:

[0029] in, This indicates the actual Joule heat generation rate after temperature correction, expressed in watts per cubic meter. The aforementioned baseline Joule heat generation rate; Temperature coefficient of resistivity of a conductor material, expressed in Kelvin, with a value of approximately 0.00393 Kelvin for copper. The current operating temperature of the conductor strand is indicated by actual measurement using a temperature sensor embedded in the stator winding or by estimation using a thermal network model, and is expressed in Kelvin or degrees Celsius. This is the reference temperature, consistent with the reference temperature used when calculating the reference resistivity. Temperature difference value. It reflects the temperature change at the current operating point relative to the reference state.

[0030] Through the temperature correction process described above, the actual Joule heat generation rate of each conductor strand is obtained. Then, the actual Joule heat generation rates of all conductor strands in each stator slot are summed to obtain the total Joule heat generation rate within the spatial partition of that stator slot. Further, all stator slots are grouped into spatial partitions based on axial segments and circumferential sectors to obtain the Joule heat generation rate distribution of the stator winding within each spatial partition. The Joule heat generation rate distribution can characterize the heat generation area distribution of the stator winding, with spatial partitions having higher Joule heat generation rates corresponding to concentrated heat generation areas. Example 2:

[0031] In specific implementation, please refer to Figure 3Before calculating the highest and average heating temperatures in the stator winding heating region distribution, the stator winding heating region distribution is first obtained. The stator winding heating region distribution represents a set of temperature values ​​within discrete spatial partitions along the axial and circumferential directions of the stator winding. These temperature values ​​can be directly collected by an array of temperature sensors placed at key locations in the stator winding, or obtained by solving a lumped-parameter thermal network model based on the Joule heat generation rate distribution. For each spatial partition, the temperature value at its center is taken as the heating temperature value of that spatial partition. The heating temperature values ​​of all spatial partitions are traversed, and the maximum value is determined through numerical comparison and recorded as the highest heating temperature value. The arithmetic mean of the heating temperature values ​​of all spatial partitions is calculated, i.e., the sum is divided by the total number of spatial partitions to obtain the average heating temperature value.

[0032] After calculating the highest and average heating temperatures, the heating intensity levels are classified. A first coefficient is set, with a value of 0.8. This first coefficient is calibrated based on the matching requirements of the stator winding's allowable temperature rise limit and thermal stress distribution characteristics. Under typical copper winding insulation conditions, selecting 0.8 ensures that the high-temperature candidate area effectively covers spatial areas with a high risk of insulation hotspots, while avoiding an excessively large high-temperature candidate area that would cause the radial depth of the cooling cavity to lose its differentiated effect.

[0033] The specific marking operation is as follows: For each spatial partition, compare the heating temperature value of the spatial partition with the product of the highest heating temperature value and a first coefficient. Spatial partitions whose heating temperature value is greater than the product of the highest heating temperature value and the first coefficient are marked as high-temperature candidate regions. Then, extract spatial partitions whose heating temperature value is less than or equal to the product of the highest heating temperature value and the first coefficient, and further filter out spatial partitions whose heating temperature value is greater than the average heating temperature value. These spatial partitions are marked as medium-temperature candidate regions. Spatial partitions whose heating temperature value is less than or equal to the average heating temperature value are marked as low-temperature candidate regions.

[0034] Next, the high-temperature, medium-temperature, and low-temperature candidate regions are processed by merging connected domains. This merging process is performed along the axial direction of the stator shell, traversing each spatial partition along the axial direction. Spatial partitions belonging to the same temperature level category and axially adjacent are merged into a continuous axial interval. After merging the high-temperature candidate regions, at least one high-temperature connected domain is obtained. The high-temperature connected domain with the largest axial span is selected, and its axial start and end positions are extracted as the start and end positions of the high-temperature segment. If multiple independent regions exist along the axial direction of the high-temperature connected domain, the connected domain with the highest total heat energy is selected as the high-temperature segment. After merging the medium-temperature candidate regions, the start and end positions of the medium-temperature segment along the axial direction of the stator shell are obtained in the same way. After merging the low-temperature candidate regions, the start and end positions of the low-temperature segment are obtained. Through connected domain merging, the high-temperature, medium-temperature, and low-temperature segments are adjacent to each other along the axial direction of the stator shell, covering the main heat-generating sections of the stator core.

[0035] After determining the axial positions of each temperature range, a multi-layered gradient cooling cavity is constructed on the inner wall of the stator housing. A first-depth cooling cavity, an annular groove extending axially along the inner wall of the stator housing, is formed in the high-temperature range, with a radial depth equal to the first radial depth. A second-depth cooling cavity, with a radial depth equal to the second radial depth, is formed in the inner wall of the stator housing corresponding to the medium-temperature range. A third-depth cooling cavity, with a radial depth equal to the third radial depth, is formed in the inner wall of the stator housing corresponding to the low-temperature range. The first radial depth is greater than the second radial depth, and the second radial depth is greater than the third radial depth. The specific values ​​of each radial depth are determined based on the heat power density of the corresponding range: the high-temperature range has the highest heat power density, requiring a larger cooling medium flow cross-sectional area and a longer heat conduction path, thus resulting in the largest radial depth; the medium-temperature range is next; and the low-temperature range has the smallest.

[0036] After completing the cavity depth machining, a first set of spiral guide ribs is installed on the inner wall of the first depth cooling cavity. The first set of spiral guide ribs consists of multiple ribs extending spirally along the inner wall of the first depth cooling cavity. The angle between the rib profile and the radial plane of the cavity is defined as the helix angle, and the first helix angle of the first set of spiral guide ribs is in the range of 10 to 20 degrees. A second set of spiral guide ribs is installed on the inner wall of the second depth cooling cavity, and the second helix angle of the second set of spiral guide ribs is in the range of 25 to 35 degrees. A third set of spiral guide ribs is installed on the inner wall of the third depth cooling cavity, and the third helix angle of the third set of spiral guide ribs is in the range of 40 to 50 degrees. The first helix angle is smaller than the second helix angle, and the second helix angle is smaller than the third helix angle. The varying helix angle is based on the following principle: in the high-temperature zone where heat generation is most severe, a smaller helix angle allows the cooling medium to achieve a larger radial-inward tangential velocity component, enhancing the impact cooling of the stator winding slot bottom insulation layer; in the low-temperature zone, a larger helix angle increases the axial flow velocity component of the cooling medium, achieving overall sweeping heat transfer with lower flow resistance. Each set of spiral guide fins is integrally formed with the inner wall of the corresponding depth cooling cavity through CNC machining or precision casting, ultimately resulting in a multi-layer gradient cooling cavity with three depth specifications and three helix angle specifications. Example 3:

[0037] In practical implementation, multiple stages of baffle assemblies are sequentially arranged from the inlet to the outlet of the multi-layer gradient cooling cavity. The inlet and outlet of the multi-layer gradient cooling cavity correspond to the axial endpoints of the cooling medium inflow and outflow, respectively. The number of stages of the baffle assembly is determined based on the total axial length of the stator shell and the required heat transfer enhancement, and is taken as an integer. The multi-stage baffle assemblies are arranged at equal intervals along the axial direction of the stator shell, and the axial spacing between adjacent stages of baffle assemblies is uniformly taken to be between three and six times the thickness of the baffle assembly itself, to ensure that a stable cooling medium flow chamber is formed between each stage of the baffle assembly.

[0038] For each stage of the baffle assembly, multiple first jet holes are arranged on the flow-facing surface of the baffle assembly at a first radial spacing. The first radial spacing refers to the distance between the centers of two adjacent first jet holes in the radial direction of the baffle. The first radial spacing is determined according to the radial depth profile of the first, second, or third depth cooling cavity, so that the first jet holes cover the radial height range of the corresponding cavity. The angle between the central axis of each first jet hole and the normal direction of the baffle assembly surface is the first jet deflection angle. The first jet deflection angle is a fixed angle within the range of 15 degrees to 25 degrees, which is used to give the jet a velocity component that deflects towards the inner wall of the stator housing or the stator winding after passing through the baffle.

[0039] On the backflow surface of each stage baffle assembly, multiple second jet holes are arranged at a second radial spacing. The second radial spacing is set in the same way as the first radial spacing, but the diameter of the second jet holes is smaller than that of the first jet holes. The angle between the central axis of each second jet hole and the normal direction of the baffle assembly surface is the second jet deflection angle. The second jet deflection angle is a fixed angle within the range of 30 degrees to 40 degrees, and it is greater than the first jet deflection angle. The larger second jet deflection angle causes the jet on the backflow surface to be injected into the next stage chamber at a more inclined angle, enhancing the circumferential turbulence of the cooling medium.

[0040] An arc-shaped flow guide groove is formed at the edge region of the backflow surface of each stage baffle assembly. The arc-shaped flow guide groove extends circumferentially along the outer edge of the backflow surface of the baffle assembly. The cross-section of the arc-shaped flow guide groove is a circular arc or parabolic concave shape, and the bottom of the groove communicates with the jet collecting groove through a channel formed inside the baffle. The jet collecting groove is an annular or semi-annular groove located at the radial center or edge of the baffle assembly, used to collect the portion of the cooling medium not guided by the second jet orifice on the backflow surface, as well as the cooling medium collected by the arc-shaped flow guide groove. Through the above processing, a baffle assembly with a first set of jet orifices, a second set of jet orifices, and an arc-shaped flow guide groove is obtained.

[0041] An arc-shaped flow guide duct is installed between two adjacent baffle assemblies. The arc height and chord length of the arc-shaped flow guide duct are determined based on the axial distance between the two adjacent baffle assemblies. The arc height and chord length are determined according to the following relationship: the chord length is equal to the axial distance between the two adjacent baffle assemblies multiplied by a correction factor between 1.0 and 1.2, used to compensate for the pipe fitting installation length; the arc height is set based on the chord length and the radius of curvature of the curved section of the arc-shaped flow guide duct, with the radius of curvature not less than three times the inner diameter of the arc-shaped flow guide duct to reduce flow resistance. After determining the arc height and chord length, the arc-shaped flow guide duct is installed between the two adjacent baffle assemblies according to these dimensions. The bow-shaped flow guide duct consists of a first straight section, a bow-shaped bend section, and a second straight section. One end of the first straight section connects to the outlet of the jet collecting groove of the preceding stage baffle assembly. The bow-shaped bend section connects the first and second straight sections, forming a bow shape for the entire duct. The convex direction of the bow-shaped bend section faces the inner wall of the stator housing, i.e., protrudes towards the central axis of the motor, to utilize the internal space of the stator and increase the heat exchange area of ​​the cooling medium flow path.

[0042] The end of the first straight section is inserted and sealed to the outlet of the jet collecting groove of the preceding baffle assembly using an interference fit and sealing ring. The end of the second straight section is inserted and sealed to the inlet of the jet distribution groove of the following baffle assembly. The jet distribution groove is a groove formed on the flow-facing surface of the following baffle assembly, communicating with the first set of jet holes on the flow-facing surface of the following baffle assembly, and is used to evenly distribute the cooling medium introduced by the arc-shaped guide pipe to each of the first jet holes. After the arc-shaped guide pipes between all adjacent baffle assemblies are installed, the jet distribution grooves of each stage of the baffle assembly are sealed and fixedly connected to the second straight section of the arc-shaped guide pipe, thus forming a cross-flow heat exchange unit containing multiple stages of baffle assemblies and arc-shaped guide pipes. The cross-flow heat exchange unit is located inside the multi-layer gradient cooling cavity, allowing the cooling medium to flow alternately through the baffle jets and the arc-shaped pipes within the cavity, forming a cross-flow path. Example 4:

[0043] In specific implementation, please refer to Figure 4 The low-temperature cooling medium supplied by the cooling medium circulation loop is simultaneously introduced into the inlet of each axial section of the multi-layer gradient cooling chamber according to a preset initial flow distribution ratio. The cooling medium circulation loop includes a circulation pump, radiator, and connecting pipes. The pressure and flow rate at the outlet of the circulation pump are controlled by a flow regulating valve group. The preset initial flow distribution ratio is determined based on the ratio of the heating power of the high-temperature, medium-temperature, and low-temperature sections. Specifically, the total Joule heat generation rate within each axial section of the high-temperature, medium-temperature, and low-temperature sections is integrated and summed to obtain the total heating power of the high-temperature, medium-temperature, and low-temperature sections. Then, the cooling medium flow rate entering the inlet of the high-temperature, medium-temperature, and low-temperature sections is distributed according to the ratio of these three total heating powers, ensuring that the cooling medium flow rate into each chamber is proportional to the total heating power of the corresponding section. The flow distribution ratio is achieved through a throttling orifice plate or proportional flow valve at the front end of each chamber inlet.

[0044] In the high-temperature section, the cooling medium enters the first-depth cooling cavity from the cavity inlet and flows axially along the first-depth cooling cavity. When the cooling medium encounters the first set of spiral guide ribs located on the inner wall of the first-depth cooling cavity, the first spiral surface of the first set of spiral guide ribs exerts a tangential deflection effect on the cooling medium. The first spiral surface is the surface of the first set of spiral guide ribs facing the direction of the cooling medium flow, and this surface forms a first helical angle with the axial direction of the first-depth cooling cavity. The first helical angle is a fixed angle within the range of 10 to 20 degrees. During the flow of the cooling medium along the first spiral surface, constrained by the rib surface, the axial mainstream direction of the cooling medium is deflected. The angle between the deflected flow direction and the radial direction of the stator housing is the first deflection angle. The first deflection angle is complementary to the first helical angle, that is, the first deflection angle is equal to 90 degrees minus the first helical angle, therefore the first deflection angle is within the range of 70 to 80 degrees. By applying the first deflection angle, the cooling medium obtains a velocity component pointing radially inward towards the stator housing.

[0045] The deflected cooling medium is guided to the radial bottom surface of the first-depth cooling cavity. The radial bottom surface of the first-depth cooling cavity refers to the wall surface at the deepest point near the outer circumference of the stator core. At the radial bottom surface, the cooling medium forms an impinging jet, which is a flow pattern where the cooling medium impacts the solid wall surface with a high normal velocity component. The impact direction of the impinging jet is towards the slot bottom insulation layer of the stator winding. The slot bottom insulation layer is located at the outermost radial end of the stator slot and is the insulation structure between the stator winding conductor and the stator core. The impinging jet directly impacts the slot bottom insulation layer, creating strong localized convective heat transfer in the impact area, causing the heat near the slot bottom insulation layer to be rapidly carried away.

[0046] After the impinging jet strikes the insulation layer at the bottom of the slot, the cooling medium diffuses outwards and flows in the opposite direction along the sidewall of the first-depth cooling cavity. The sidewall of the first-depth cooling cavity is an axially extending annular wall, including an outer wall near the outside of the stator housing and an inner wall near the inner cavity of the stator. The sidewall guides the backflow of the cooling medium, causing the diffused cooling medium to flow back into the main channel of the first-depth cooling cavity along the backflow side of the first helical surface. The reflowed cooling medium is again given a tangential velocity component when flowing through the next section of the first helical surface. This cycle creates a first helical turbulence within the first-depth cooling cavity, impacting the stator winding in a radially inward direction. This first helical turbulence combines the macroscopic directionality of helical flow with the high diffusivity of turbulent pulsations, and the radially inward impact component enhances heat exchange at the interface of the insulation layer at the bottom of the slot.

[0047] In the intermediate temperature zone, the cooling medium enters the second-depth cooling cavity from the cavity inlet of the intermediate temperature zone. When flowing through the second set of spiral guide fins, the second spiral helix angle of the second set of spiral guide fins is within the range of 25 to 35 degrees. The corresponding second spiral surface applies a second tangential velocity component to the cooling medium. The radial component of the second tangential velocity component is smaller than the radial component of the first tangential velocity component, while the circumferential component is larger than the circumferential component of the first tangential velocity component. This causes the cooling medium to form a second spiral turbulence that sweeps across the stator windings circumferentially within the second-depth cooling cavity. Circumferential sweeping flow refers to the flow of the cooling medium along the stator circumference with a relatively strong velocity component around the outer circumference of the stator core. This flow pattern is beneficial for uniformly covering multiple stator slots in the circumferential direction of the stator windings, achieving circumferentially balanced heat transfer.

[0048] In the low-temperature section, the cooling medium enters the third-depth cooling cavity from the cavity inlet of the low-temperature section. When flowing through the third set of spiral guide fins, the third spiral helix angle of the third set of spiral guide fins is in the range of 40 degrees to 50 degrees, and the corresponding third spiral face applies a third tangential velocity component to the cooling medium. The axial component of the third tangential velocity component is greater than the axial component of the second tangential velocity component, causing the cooling medium to form a third spiral turbulence that sweeps across the stator winding axially in the third-depth cooling cavity. Axial sweeping flow refers to the cooling medium passing through rapidly along the length of the stator core at a higher axial velocity, reducing the flow pressure drop of the cooling medium in the low-temperature section while ensuring basic heat exchange capacity. The first spiral turbulence in the high-temperature section, the second spiral turbulence in the medium-temperature section, and the third spiral turbulence in the low-temperature section are formed simultaneously in the same operating cycle, respectively performing differentiated layered cascaded heat exchange on different axial sections of the stator winding, completing the layered cascaded heat exchange process of the stator winding's heating area. Example 5:

[0049] In specific implementation, please refer to Figure 5 During the heat exchange process, the cooling medium flowing through the multi-layer gradient cooling cavity sequentially passes through a multi-stage baffle assembly arranged within the cavity. As the cooling medium flows axially to each stage of the baffle assembly, it impacts the frontal surface of the baffle assembly. Multiple first jet holes are arranged at a first radial spacing on the frontal surface, forming a first set of jet holes. Under the impact, a portion of the cooling medium enters the first set of jet holes and is ejected from them at a first jet deflection angle, forming a jet. The first jet deflection angle is the angle between the central axis of the first jet hole and the normal direction of the baffle assembly's plate surface, and is a fixed angle value within the range of 15 to 25 degrees. Simultaneously, the cooling medium not drawn by the first set of jet holes is blocked and guided by the solid plate surface of the baffle assembly's frontal surface, flowing along the radial edge region of the baffle assembly.

[0050] The jet passing through the first set of jet holes enters the backflow side of the baffle assembly. Multiple second jet holes are arranged at a second radial spacing on the backflow surface, forming a second set of jet holes. The diameter of the second jet holes is smaller than that of the first jet holes. After the jet reaches the backflow surface, a portion of the cooling medium passes through the second set of jet holes, forming a secondary jet with a second jet deflection angle. The second jet deflection angle is the angle between the central axis of the second jet holes and the normal direction of the baffle assembly surface. The second jet deflection angle is a fixed angle value within the range of 30 to 40 degrees, and it is greater than the first jet deflection angle. The cooling medium not drawn by the second set of jet holes, as well as a portion of the cooling medium flowing along the backflow surface wall, flows into an arc-shaped guide channel opened at the edge region of the backflow surface. The arc-shaped flow channel extends circumferentially along the outer edge of the backflow surface. The bottom of the arc-shaped flow channel is connected to the jet collection channel through an internal channel, so that all the cooling medium entering the arc-shaped flow channel is gathered into the jet collection channel.

[0051] The cooling medium collected by the jet collecting trough enters the arc-shaped guide pipe. The arc-shaped guide pipe is installed between the preceding and following baffle assemblies. After exiting the jet collecting trough, the cooling medium flows along the first straight section of the arc-shaped guide pipe towards the arc-shaped bend section. Within the arc-shaped bend section, the cooling medium changes its flow direction under the constraint of the bend wall, with the convex direction of the arc-shaped bend section facing towards the inner wall of the stator housing. After passing through the arc-shaped bend section, the cooling medium enters the second straight section, flows along it, and is delivered to the inlet of the jet distribution trough of the following baffle assembly.

[0052] The jet distribution groove is a distribution recess formed on the flow-facing surface of the subsequent stage baffle assembly. It connects to the first jet holes of the first set of jet holes on the flow-facing surface of the subsequent stage baffle assembly. Cooling medium, fed in from the arc-shaped guide pipe, enters the jet distribution groove and undergoes pressure equalization within it, ensuring uniform flow of the cooling medium into each of the first jet holes of the first set of jet holes in the subsequent stage baffle assembly. This completes the guidance and redistribution of the cooling medium from the preceding stage chamber to the subsequent stage chamber. After alternating jets from the multi-stage baffle assembly and the guidance from the arc-shaped guide pipe, the high-temperature cooling medium, after heat exchange, flows out from the cavity outlet of the multi-layer gradient cooling chamber. The high-temperature cooling medium flowing out of the cavity outlet is guided by pipelines to the cooling medium circulation loop, which includes a radiator and a circulation pump. The high-temperature cooling medium dissipates heat to the external environment in the radiator, and the cooled low-temperature cooling medium is then pumped back to the cavity inlets of the multi-layer gradient cooling chamber by the circulation pump.

[0053] The above description is merely a specific embodiment of this application, but the scope of protection of this application is not limited thereto. Any changes or substitutions that can be easily conceived by those skilled in the art within the scope of the technology disclosed in this application should be included within the scope of protection of this application.

Claims

1. A stator cooling system for a permanent magnet direct drive motor, characterized in that, The system performs the following operations: The operating condition acquisition module acquires real-time operating condition data of the permanent magnet direct drive motor; the heat mapping module determines the distribution of the stator winding heat-generating area of ​​the permanent magnet direct drive motor in the current operating cycle based on the real-time operating condition data. The cavity construction module constructs a multi-layer gradient cooling cavity on the inner wall of the stator housing of the permanent magnet direct drive motor according to the distribution of the heating area of ​​the stator winding. The multi-layer gradient cooling cavity is segmented along the axial direction of the stator housing. The flow guiding module arranges cross-flow heat exchange units in the multi-layer gradient cooling cavity, and the cross-flow heat exchange units are connected to the cooling medium circulation loop outside the stator housing. The circulating heat dissipation module performs layered cascaded heat exchange on the stator winding heating area through the cross-flow heat exchange unit, and guides the high-temperature cooling medium after heat exchange to the cooling medium circulation loop for heat dissipation.

2. The stator cooling system for a permanent magnet direct drive motor according to claim 1, characterized in that, Based on the real-time operating condition data, the distribution of the stator winding heating area of ​​the permanent magnet direct drive motor in the current operating cycle is determined, including: Extract the stator phase current timing waveform and rotor position angle sequence of the permanent magnet direct drive motor from the real-time operating condition data; The fundamental and harmonic components of the stator phase current time sequence waveform are separated to obtain the fundamental current amplitude sequence and the harmonic current distortion rate sequence. Based on the rotor position angle sequence, the fundamental current amplitude sequence and the harmonic current distortion rate sequence are subjected to spatiotemporal synchronous mapping to generate the current density distribution spectrum of the stator winding along the circumferential direction. Based on the current density distribution spectrum and the resistivity temperature coefficient of the conductor material of the stator winding, the Joule heat generation rate distribution of the stator winding in each spatial partition is calculated to obtain the heat generation area distribution of the stator winding.

3. The stator cooling system for a permanent magnet direct drive motor according to claim 1, characterized in that, Based on the distribution of the heating areas in the stator windings, a multi-layered gradient cooling cavity is constructed on the inner wall of the stator housing of the permanent magnet direct drive motor, including: The distribution of the heating area of ​​the stator winding is classified according to the heating intensity level, and the axial section of the stator shell is divided into a high temperature section, a medium temperature section and a low temperature section. A first-depth cooling cavity is formed on the inner wall of the stator housing corresponding to the high-temperature zone, a second-depth cooling cavity is formed on the inner wall of the stator housing corresponding to the medium-temperature zone, and a third-depth cooling cavity is formed on the inner wall of the stator housing corresponding to the low-temperature zone. The radial depth of the first-depth cooling cavity is greater than the radial depth of the second-depth cooling cavity, and the radial depth of the second-depth cooling cavity is greater than the radial depth of the third-depth cooling cavity. A first set of spiral guide ribs is provided on the inner wall of the first depth cooling cavity, a second set of spiral guide ribs is provided on the inner wall of the second depth cooling cavity, and a third set of spiral guide ribs is provided on the inner wall of the third depth cooling cavity. The spiral helix angle of the first set of spiral guide ribs is smaller than that of the second set of spiral guide ribs, and the spiral helix angle of the second set of spiral guide ribs is smaller than that of the third set of spiral guide ribs, thus obtaining the multi-layer gradient cooling cavity.

4. The stator cooling system for a permanent magnet direct drive motor according to claim 1, characterized in that, A cross-flow heat exchange unit is arranged in the multi-layer gradient cooling cavity, including: A multi-stage baffle assembly is arranged sequentially from the cavity inlet to the cavity outlet of the multi-layer gradient cooling cavity, and the multi-stage baffle assembly is arranged at equal intervals along the axial direction of the stator housing; A first set of jet holes and a second set of jet holes are respectively opened on the front and back surfaces of each stage baffle assembly, wherein the diameter of the first set of jet holes is larger than the diameter of the second set of jet holes. An arc-shaped guide pipe is installed between two adjacent baffle assemblies. The inlet end of the arc-shaped guide pipe is connected to the jet collection groove of the previous baffle assembly, and the outlet end of the arc-shaped guide pipe is connected to the jet distribution groove of the next baffle assembly. The jet distribution grooves of each stage of the baffle assembly are sealed and fixedly connected to the bow-shaped guide pipe to form the cross-flow heat exchange unit.

5. The stator cooling system for a permanent magnet direct drive motor according to claim 1, characterized in that, The stator winding heating region is subjected to layered cascade heat exchange through the cross-flow heat exchange unit, including: The low-temperature cooling medium supplied by the cooling medium circulation loop is introduced into the cavity inlet of each axial section of the multi-layer gradient cooling cavity according to a preset initial flow distribution ratio. When the cooling medium in the high-temperature zone flows through the first set of spiral guide ribs, the first set of spiral guide ribs applies a first tangential velocity component to the cooling medium, causing the cooling medium to form a first spiral turbulence that impacts the stator winding in a radially inward direction within the first depth cooling cavity; When the cooling medium in the medium temperature zone flows through the second set of spiral guide ribs, the second set of spiral guide ribs applies a second tangential velocity component to the cooling medium, causing the cooling medium to form a second spiral turbulence that sweeps the stator winding in the circumferential direction within the second depth cooling cavity; When the cooling medium in the low-temperature section flows through the third set of spiral guide ribs, the third set of spiral guide ribs applies a third tangential velocity component to the cooling medium, causing the cooling medium to form a third spiral turbulence that sweeps across the stator winding axially within the third depth cooling cavity, thus completing the layered cascade heat exchange of the stator winding heating area.

6. The stator cooling system for a permanent magnet direct drive motor according to claim 4, characterized in that, The method of opening a first set of jet holes and a second set of jet holes on the front and back surfaces of each stage of the baffle assembly includes: On the frontal surface of each stage of the baffle assembly, a plurality of first jet holes are arranged at a first radial spacing, and the angle between the central axis of each first jet hole and the normal direction of the baffle assembly is the first jet deflection angle. On the backflow surface of each stage baffle assembly, a plurality of second jet holes are arranged at a second radial spacing. The angle between the central axis of each second jet hole and the normal direction of the baffle assembly is the second jet deflection angle, which is greater than the first jet deflection angle. An arc-shaped flow channel is formed at the edge region of the back flow surface of each stage of the baffle assembly. The bottom of the arc-shaped flow channel is connected to the jet collection channel to obtain a baffle assembly with the first set of jet holes and the second set of jet holes.

7. The stator cooling system for a permanent magnet direct drive motor according to claim 4, characterized in that, The method of erecting an arc-shaped flow guide pipe between two adjacent baffle assemblies includes: The bow-shaped arch height and bow-shaped chord length of the bow-shaped guide pipe are determined based on the axial spacing between the two adjacent baffle assemblies. According to the bow height and bow chord length, the first straight section, the bow curved section and the second straight section of the bow guide pipe are arranged between the two adjacent baffle assemblies, so that the protrusion direction of the bow curved section faces the inner wall of the stator housing; The end of the first straight section is inserted and sealed to the outlet of the jet collecting groove of the preceding baffle assembly, and the end of the second straight section is inserted and sealed to the inlet of the jet distribution groove of the following baffle assembly, thus completing the installation of the bow-shaped guide pipe between two adjacent baffle assemblies.

8. The stator cooling system for a permanent magnet direct drive motor according to claim 2, characterized in that, The step of calculating the Joule heat generation rate distribution of the stator winding in each spatial partition based on the current density distribution spectrum and the resistivity temperature coefficient of the conductor material of the stator winding includes: According to the arrangement of conductors in the slots of the stator winding, the current density distribution map is mapped onto each conductor strand in each stator slot to obtain the strand current density value of each conductor strand. The reference Joule heat generation rate of each conductor strand is calculated based on the strand current density value of each conductor strand and the reference resistivity of the conductor material. Based on the temperature difference between the current operating temperature and the reference temperature of each conductor strand, and in conjunction with the resistivity temperature coefficient, the reference Joule heat generation rate is temperature-corrected to obtain the actual Joule heat generation rate of each conductor strand. The actual Joule heat generation rates of all conductor strands in each stator slot are summed to obtain the Joule heat generation rate distribution of the stator winding in each spatial partition.

9. The stator cooling system for a permanent magnet direct drive motor according to claim 3, characterized in that, The process of classifying the heating area distribution of the stator winding into heating intensity levels, and dividing the axial section of the stator housing into high-temperature, medium-temperature, and low-temperature sections, includes: Calculate the highest and average heating temperature values ​​in the heating region distribution of the stator winding; Regions in the heat generation area distribution whose heat generation temperature value is greater than the product of the highest heat generation temperature value and the first coefficient are marked as high temperature candidate regions; regions whose heat generation temperature value is between the product of the average heat generation temperature value and the product of the highest heat generation temperature value and the first coefficient are marked as medium temperature candidate regions; and regions whose heat generation temperature value is less than or equal to the average heat generation temperature value are marked as low temperature candidate regions. The first coefficient is 0.

8. The high-temperature candidate region, the medium-temperature candidate region, and the low-temperature candidate region are respectively subjected to connected component merging processing to obtain the starting and ending positions of the high-temperature segment, the medium-temperature segment, and the low-temperature segment in the axial direction of the stator housing.

10. The stator cooling system for a permanent magnet direct drive motor according to claim 5, characterized in that, When the cooling medium in the high-temperature zone flows through the first set of spiral guide ribs, the first set of spiral guide ribs applies a first tangential velocity component to the cooling medium, including: When the cooling medium flows along the axial direction of the first depth cooling cavity, the first spiral face of the first set of spiral guide ribs generates a tangential deflection effect on the cooling medium, causing the axial mainstream direction of the cooling medium to be deflected to a first deflection angle with the radial direction of the stator housing. The deflected cooling medium is guided to the radial bottom surface of the first depth cooling cavity, so that the cooling medium forms an impact jet at the radial bottom surface, and the impact direction of the impact jet is directed towards the slot bottom insulation layer of the stator winding. After the impact jet strikes the insulating layer at the bottom of the tank, the cooling medium is guided back through the side wall of the first depth cooling cavity, so that the backflowed cooling medium re-enters the main channel of the first depth cooling cavity along the first spiral surface, thus obtaining a cooling medium carrying the first tangential velocity component.

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