High-speed oil-cooled flat wire motor stator oil circuit structure design method

Abstract

The invention provides a high-speed oil-cooled flat wire motor stator oil path structure design method, which comprises the following steps of: sequentially establishing a structure model, a loss model and a thermal analysis model of a high-speed flat wire motor based on the thoughts of a thermal network method and a finite element method; determining an optimal design scheme of the motor oil cooling system by gradually simulating and calculating temperature rise conditions of important positions in the motor when different spraying ring structures and iron core oil path layout are selected, and finally constructing a test motor entity according to the optimal design scheme determined by simulation and carrying out a bench test to verify the reasonability of the scheme. Therefore, an accurate and efficient oil cooling system design theory suitable for the flat wire winding permanent magnet driving motor is formed.

Description

Technical Field

[0001] The invention belongs to the technical field of motor manufacturing for new energy vehicles, and specifically relates to a method for designing a stator oil circuit structure of a high-speed oil-cooled flat wire motor. Background Art

[0002] At present, flat wire winding permanent magnet synchronous motors are increasingly being used in new energy vehicles due to their advantages such as high slot fill rate, high power density and efficiency, and good heat dissipation performance. When the motor is running at high speed, due to the large cross-sectional area of ​​the flat wire, the skin effect will be enhanced under the action of high-frequency current, the AC loss will increase, and the core loss will also increase with the increase of speed, which puts higher requirements on the heat dissipation system of the motor. The existing heat dissipation system suitable for flat wire motors mainly adopts water cooling or oil-water mixed structure, both of which have some disadvantages. For example, the water cooling structure is only suitable for medium and low speed motors, and it is difficult to meet the heat dissipation requirements of high-speed motors; the oil-water mixed structure uses water channels to cool the stator core, and exchanges heat through the casing oil channel and the water channel to reduce the water temperature, resulting in poor heat dissipation effect on the end windings. It is often necessary to cooperate with the oil injection pipe or oil injection ring to spray oil on the end windings for cooling, which not only increases the complexity of the cooling system, but also makes it difficult to avoid the problem of uneven oil spraying. Some recent existing technologies use spray cooling and pure oil cooling. Although they can improve the heat dissipation effect to a certain extent, they have many adverse effects on motor performance, losses, etc. It can be seen that there is still a lot of room for improvement in the overall design and oil circuit layout of these new motor heat dissipation systems. At this stage, this field also urgently needs a set of effective design theories. Summary of the invention

[0003] In view of this, in order to solve the technical problems existing in the art, the present invention provides a method for designing a stator oil circuit structure of a high-speed oil-cooled flat wire motor, which specifically includes the following steps:

[0004] Step 1: Use finite element simulation software to establish a high-speed flat wire permanent magnet drive motor model, including a two-dimensional magnetic field model and a three-dimensional structural model of the motor;

[0005] Step 2: Select the appropriate stator end spray ring type and oil circuit layout, and design the overall structure of the oil cooling system;

[0006] Step 3: Consider the motor's winding loss, core loss, and permanent magnet eddy current loss to establish a motor electromagnetic loss model;

[0007] Step 4: Utilize the motor electromagnetic loss model established in step 3, and combine the speed-torque mechanical characteristics of the motor to calculate the loss distribution cloud diagrams under rated working conditions and peak working conditions, and select multiple typical working conditions corresponding to the rated working conditions and peak working conditions to calculate the motor electromagnetic loss and temperature rise respectively;

[0008] Step 5: Perform finite element simulation based on the three-dimensional structural model to extract the fluid domain model of the motor, and establish a three-dimensional thermal analysis model of the motor for finite element simulation of the motor temperature rise under rated conditions and peak conditions; set the simulation boundary conditions and the cooling oil circuit inlet flow and inlet temperature;

[0009] Step 6: Design different combinations of the number, diameter and shape of the spray holes of the spray ring, and use the fluid domain three-dimensional thermal analysis model to simulate the winding temperature and stator core temperature cloud map to determine the optimal spray ring specifications;

[0010] Step 7: When the steady-state average temperature of the winding with the best spray ring specification obtained by simulation in step 6 exceeds the corresponding threshold, the stator core oil circuits set at the end windings on both sides are simulated and optimized, including: selecting different stator core oil circuit layouts, and performing finite element simulation to calculate the stator temperature field corresponding to each oil circuit layout, and using fluid domain model extraction and three-dimensional thermal analysis model to obtain winding temperature and core temperature cloud maps, thereby determining the best stator core oil circuit layout, and then determining the optimal oil cooling system structure;

[0011] Step 8: For the determined optimal oil cooling system structure, a three-dimensional thermal analysis model is used to simulate the stator temperature distribution cloud map under different typical working conditions, and the distribution areas corresponding to the highest temperatures of the winding and stator core are determined, which are used as the basis for subsequent motor cooling system optimization;

[0012] Step 9. Build a high-speed flat-wire permanent magnet drive test motor entity based on the optimal oil cooling system structure, and build a motor temperature rise test platform based on the test motor entity; drive the test motor entity to operate under rated conditions and peak conditions through the test platform, and measure the temperature rise of the end winding and stator core at the same time, so as to verify the effect of the designed optimal oil cooling system structure.

[0013] Furthermore, in step one, the two-dimensional electromagnetic field model of the motor is established by using Motor CAD software, and the three-dimensional structural model of the motor is established by using Solid Works software.

[0014] Furthermore, in step 2, an oil circuit layout consisting of an oil inlet pipeline, two spray rings, a stator core oil circuit and an oil outlet pipeline is specifically designed; wherein the spray rings are arranged at both ends in the casing, and the stator core is located between the two spray rings; after the cooling oil flows from the outside of the casing into the inside through the oil pipeline, part of it is distributed to a spray ring, and is sprayed out from the spray holes distributed circumferentially on the spray ring under the action of oil pressure, so that the end winding on one side close to it is cooled; the other part of the cooling oil flows to the other spray ring through the stator core oil circuit, and the stator core and the end winding on the other side are cooled during the flow process; the cooling oil after cooling flows out of the casing through the oil outlet pipeline and enters the next cooling cycle.

[0015] Furthermore, the motor electromagnetic loss model established in step 3 specifically includes:

[0016] Winding loss model:

[0017] P Cu =P DC +P AC

[0018] Where P Cu is the total winding loss, P DC is the DC loss of the winding; P AC is the winding AC loss;

[0019] Among them, the DC loss P DC Calculated using the following formula:

[0020] P DC =mI 2 R DC

[0021] In the formula, m is the number of phases of the motor, I is the effective value of the motor phase current, R DC is the DC resistance of the winding, which is specifically expressed as:

[0022]

[0023] In the formula, l Cu is the average half-turn length of the winding, N Φ is the number of series turns per phase, σ Cu is the conductivity of copper, N is the number of parallel branches, and S is the cross-sectional area of ​​the winding;

[0024] AC loss P AC Calculated using the following formula:

[0025]

[0026] In the formula, k s is the AC loss coefficient, B is the magnetic flux density, ω is the electrical angular frequency, d is the conductor thickness, W is the flat wire width, and l is the conductor length;

[0027] Core loss model:

[0028]

[0029] Where P ir is the core loss, P h is the hysteresis loss, P e is the eddy current loss, P ex is the additional loss, K h and ɑ are the hysteresis loss coefficients, K eis the eddy current loss coefficient, K ex is the additional loss coefficient, B m is the peak value of magnetic flux density, f is the repetitive magnetization frequency;

[0030] Permanent magnet eddy current loss model:

[0031]

[0032] Where P PM is the eddy current loss of permanent magnet, L a is the axial length of the permanent magnet, L b is the average width of the permanent magnet, V is the volume of the permanent magnet, ρ pm is the permanent magnet resistivity, K pm is the permanent magnet eddy current loss coefficient, f pm is the magnetic field alternating frequency, B pm is the maximum magnetic flux density of the permanent magnet.

[0033] Furthermore, in step five, the motor fluid domain model is extracted using Ansys Space Claim software, and a three-dimensional thermal analysis model is established using Ansys Fluent software.

[0034] Furthermore, in the simulation of step six, the maximum temperature of 180° C. allowed by the motor insulation grade H is used as the threshold of the steady-state average temperature of the winding, and when the determined optimal injection ring specification exceeds this threshold, the core oil circuit simulation optimization of step seven is performed.

[0035] Furthermore, the core oil circuit layout selected in step seven includes: a layout form in which multiple axially extending straight oil circuits are evenly arranged outside the stator core, and various staggered oil circuit layout forms including straight oil circuits, and the cross-sectional shape and size specifications at each position of the oil circuit are set.

[0036] Furthermore, in step nine, a motor temperature rise test platform consisting of a test motor entity, a dynamometer, a controller, a thermometer, a power analyzer, and a constant temperature oil tank is specifically constructed; wherein the controller is used to drive and control the operation of the test motor entity; the test motor entity is connected to the dynamometer through a coupling, and various motor operating conditions are loaded through the dynamometer; thermocouples connected to the thermometer are provided at the end windings and stator core slots of the test motor entity to measure the temperature rise at the corresponding positions; the power analyzer is used to measure the motor power and speed under various working conditions; the constant temperature oil tank is connected to the oil cooling system in the test motor entity and provides cooling oil circulation for it.

[0037] The method for designing the stator oil circuit structure of a high-speed oil-cooled flat wire motor provided by the present invention is based on the ideas of the thermal network method and the finite element method, and sequentially establishes the structural model, loss model and thermal analysis model of the high-speed flat wire motor, and then determines the optimal design scheme of the motor oil cooling system by gradually simulating and calculating the temperature rise of each important position inside the motor when different spray ring structures and core oil circuit layouts are selected. Finally, a test motor entity is built for the optimal design scheme determined by the simulation and a bench test is carried out to verify the rationality of the scheme, thereby forming a set of accurate and efficient oil cooling system design theories suitable for flat wire winding permanent magnet drive motors. BRIEF DESCRIPTION OF THE DRAWINGS

[0038] Figure 1 A schematic diagram of the structure of a high-speed flat wire winding motor to which the method provided by the present invention is applicable;

[0039] Figure 2 A schematic diagram of an oil cooling system structure that can be selected when executing the method of the present invention;

[0040] Figure 3 A schematic diagram of a spray ring structure that can be selected when performing the method of the present invention;

[0041] Figure 4 The present invention is a schematic diagram of optional stator core oil circuit layouts for executing the method of the present invention. DETAILED DESCRIPTION

[0042] The technical solution of the present invention will be described clearly and completely below in conjunction with the accompanying drawings. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0043] The method provided by the present invention specifically comprises the following steps:

[0044] Step 1: Use finite element simulation software to establish a high-speed flat wire permanent magnet drive motor model, including a two-dimensional magnetic field model and a three-dimensional structural model of the motor;

[0045] Step 2: Select the appropriate stator end spray ring type and oil circuit layout, and design Figure 2 The overall structure of the oil cooling system shown;

[0046] Step 3: Consider the motor's winding loss, core loss, and permanent magnet eddy current loss to establish a motor electromagnetic loss model;

[0047] Step 4: Utilize the motor electromagnetic loss model established in step 3, and combine the speed-torque mechanical characteristics of the motor to calculate the loss distribution cloud diagrams under rated working conditions and peak working conditions, and select multiple typical working conditions corresponding to the rated working conditions and peak working conditions to calculate the motor electromagnetic loss and temperature rise respectively;

[0048] Step 5: Perform finite element simulation based on the three-dimensional structural model to extract the fluid domain model of the motor, and establish a three-dimensional thermal analysis model of the motor for finite element simulation of the motor temperature rise under rated conditions and peak conditions; set the simulation boundary conditions and the cooling oil circuit inlet flow and inlet temperature;

[0049] Step 6: Design different combinations of the number, diameter and shape of the spray holes of the spray ring, and use the fluid domain three-dimensional thermal analysis model to simulate the winding temperature and stator core temperature cloud map to determine the optimal spray ring specifications;

[0050] Step 7: When the steady-state average temperature of the winding with the best spray ring specification obtained by simulation in step 6 exceeds the corresponding threshold, the stator core oil circuits set at the end windings on both sides are simulated and optimized, including: selecting different stator core oil circuit layouts, and performing finite element simulation to calculate the stator temperature field corresponding to each oil circuit layout, and using fluid domain model extraction and three-dimensional thermal analysis model to obtain winding temperature and core temperature cloud maps, thereby determining the best stator core oil circuit layout, and then obtaining the optimal oil cooling system structure;

[0051] Step 8: For the determined optimal oil cooling system structure, a three-dimensional thermal analysis model is used to simulate the stator temperature distribution cloud map under different typical working conditions, and the distribution areas corresponding to the highest temperatures of the winding and stator core are determined, which are used as the basis for subsequent motor cooling system optimization;

[0052] Step 9. Build a high-speed flat-wire permanent magnet drive test motor entity based on the determined optimal oil cooling system structure, and build a motor temperature rise test platform based on the test motor entity; drive the test motor entity to operate under rated conditions and peak conditions through the test platform, and measure the temperature rise of the end winding and stator core at the same time, so as to verify the effect of the designed optimal oil cooling system structure.

[0053] In a preferred embodiment of the present invention, firstly in step 1, a two-dimensional electromagnetic field model of the motor is established using Motor CAD software, and a three-dimensional structural model of the motor is established using SolidWorks software. Figure 1 The specific motor structure is shown, and its parameters are shown in the following Table 1

[0054] Table 1 Key parameters of motor

[0055]

[0056] In order to improve the motor slot fill rate and power density, the flat wire motor winding design uses a 7-layer distributed winding with a pitch of 5.

[0057] In step 2, the oil circuit layout consisting of the oil inlet pipeline, two spray rings, the stator core oil circuit and the oil outlet pipeline is specifically designed, such as Figure 2 As shown. The spray rings are arranged at both ends of the casing, and the stator core is located between the two spray rings; the cooling oil flows from the outside of the casing into the inside through the oil pipeline, and then part of it is distributed to a spray ring, and sprayed out from the spray holes distributed circumferentially on the spray ring under the action of oil pressure, so that the end winding close to it is cooled; the other part of the cooling oil flows to the other spray ring through the stator core oil path, and the stator core and the end winding on the other side are cooled during the flow process; the cooling oil after cooling flows out of the casing through the oil outlet pipeline and enters the next cooling cycle.

[0058] In step three, the electromagnetic loss model of the motor is established, and in step four, each loss under rated working condition and peak working condition is simulated and calculated to obtain the corresponding loss distribution cloud map. As the speed increases, the winding loss, core loss and permanent magnet eddy current loss of the motor further increase. The winding loss is the main body of the electromagnetic loss of the motor, and the eddy current loss of the permanent magnet is very small. The winding loss at the rated working condition peak speed is 1.75 times that at the rated speed. The winding loss at the peak working condition peak speed is 1.59 times that at the rated speed.

[0059] Considering that the electric vehicle has a high current, large loss, and more serious heat generation when the electric motor is started, accelerated, and climbed. Four typical operating points where the motor is prone to heat up are selected to calculate the electromagnetic loss and temperature rise of the motor, as shown in Table 2.

[0060] Table 2 Electromagnetic losses of motors under typical working conditions

[0061]

[0062] In step 5, the motor fluid domain model was extracted using Ansys Space Claim software, and a three-dimensional thermal analysis model was established using Ansys Fluent software. The boundary conditions for the simulation were set, with mass inlet selected as the inlet type, 7L / min as the inlet flow rate, 80°C as the inlet temperature, and outflow boundary selected as the outlet type.

[0063] In the simulation of step 6, three different spray hole quantity schemes of 12, 15, and 18 are selected, and the simulation results shown in Table 3 are obtained:

[0064] Table 3 Simulation results of different nozzle number schemes

[0065]

[0066] Taking temperature as the criterion, it can be seen that the spray cooling effect is better when the number of spray holes is 15, so it is determined as the optimal number of spray holes.

[0067] Choose two different spray hole diameters of 1mm and 2mm, and a cone-shaped countersunk spray hole shape with an upper hole diameter of 1.6mm and a lower hole diameter of 1mm, such as Figure 3 After simulation of different nozzle aperture schemes, the results are shown in Table 4:

[0068] Table 4 Simulation results of different nozzle hole diameter schemes

[0069]

[0070] By comparison, it can be determined that the conical countersunk hole is the best shape and size of the spray hole.

[0071] According to the temperature rise cloud map, when the above-mentioned optimal spray ring specifications are used, the steady-state average temperature of the winding has exceeded the 180°C threshold, so the core oil circuit is further simulated and optimized in step seven. First, 45 axially extended straight oil circuits are evenly arranged on the outside of the stator core. The cross-section of the oil circuit is a fan-shaped circuit with a height of 3mm and an arc of 6°. On the basis of this straight oil circuit, the stator core staggered oil circuit is designed. Specifically, the stator core laminations are divided into 5 sections, each section is rotated 5°, so that each oil circuit intersects with half of the adjacent oil circuit. The structure and cross-sectional form of the two oil circuits are as follows: Figure 4 The results of the stator temperature field simulation when two oil circuit layouts are used are shown in Table 5:

[0072] Table 5 Simulation results of different stator core oil channel structures

[0073]

[0074] Combined with the temperature cloud map, the best core oil circuit layout and the ultimate optimal oil cooling system are determined, namely, the number of spray holes in the spray ring is 15, the conical countersunk hole structure, a total of 45 staggered stator core oil circuit structures, and the oil circuit cross-section is fan-shaped.

[0075] In step eight, the temperature rise corresponding to the rated working condition and the peak working condition is simulated for the optimal oil cooling system. Under the rated working condition, the maximum temperature of the flat wire winding is 98.73°C, the maximum temperature of the stator core is 94.13°C, the maximum temperature of the rotor core is 85.78°C, and the maximum temperature of the magnetic steel is 85.6°C. Under the peak working condition, the motor has a peak power of 94kW and a speed of 6000rpm, the maximum temperature of the flat wire winding is 130.67°C, the maximum temperature of the stator core is 118.88°C, the maximum temperature of the rotor core is 100.57°C, and the maximum temperature of the magnetic steel is 99.03°C.

[0076] In the final step nine, a motor temperature rise test platform consisting of a test motor entity, a dynamometer, a controller, a thermometer, a power analyzer, and a constant temperature oil tank is constructed; wherein, the controller is used to drive and control the operation of the test motor entity; the test motor entity is connected to the dynamometer through a coupling, and various motor operating conditions are loaded through the dynamometer; thermocouples connected to the thermometer are provided at the end windings and stator core slots of the test motor entity to measure the temperature rise at the corresponding positions; the power analyzer is used to measure the motor power and speed under various working conditions; the constant temperature oil tank is connected to the oil cooling system in the test motor entity and provides cooling oil for it.

[0077] Finally, after platform test verification, the results showed that under the rated operating conditions of 4500rpm, 85Nm, and 40kW, the temperature rise curve of the flat wire winding end of the motor after running for 30 minutes was basically consistent with the simulation results. The maximum temperature of the winding end was around 160℃, which was lower than the temperature resistance limit of the winding insulation grade of 180℃, and both met the standard requirements well.

[0078] It should be understood that the size of the serial numbers of the steps in the embodiment of the present invention does not mean the order of execution. The execution order of each process should be determined by its function and internal logic, and should not constitute any limitation on the implementation process of the embodiment of the present invention.

[0079] Although embodiments of the present invention have been shown and described, it will be appreciated by those skilled in the art that various changes, modifications, substitutions and variations may be made to the embodiments without departing from the principles and spirit of the present invention, and that the scope of the present invention is defined by the appended claims and their equivalents.

Claims

1. A method for designing a stator oil circuit structure of a high-speed oil-cooled flat wire motor, characterized in that: The specific steps include: Step 1: Use finite element simulation software to establish a high-speed flat wire permanent magnet drive motor model, including a two-dimensional magnetic field model and a three-dimensional structural model of the motor; Step 2: Select the appropriate stator end spray ring type and oil circuit layout, and design the overall structure of the oil cooling system; Step 3: Consider the motor's winding loss, core loss, and permanent magnet eddy current loss to establish a motor electromagnetic loss model; Step 4: Utilize the motor electromagnetic loss model established in step 3, and combine the speed-torque mechanical characteristics of the motor to calculate the loss distribution cloud diagrams under rated working conditions and peak working conditions, and select multiple typical working conditions corresponding to the rated working conditions and peak working conditions to calculate the motor electromagnetic loss and temperature rise respectively; Step 5: Perform finite element simulation based on the three-dimensional structural model to extract the fluid domain model of the motor, and establish a three-dimensional thermal analysis model of the motor for finite element simulation of the motor temperature rise under rated conditions and peak conditions; set the simulation boundary conditions and the cooling oil circuit inlet flow and inlet temperature; Step 6: Design different combinations of the number, diameter and shape of the spray holes of the spray ring, and use the fluid domain three-dimensional thermal analysis model to simulate the winding temperature and stator core temperature cloud map to determine the optimal spray ring specifications; Step 7: When the steady-state average temperature of the winding with the best spray ring specification obtained by simulation in step 6 exceeds the corresponding threshold, the stator core oil circuits set at the end windings on both sides are simulated and optimized, including: selecting different stator core oil circuit layouts, and performing finite element simulation to calculate the stator temperature field corresponding to each oil circuit layout, and using fluid domain model extraction and three-dimensional thermal analysis model to obtain winding temperature and core temperature cloud maps, thereby determining the best stator core oil circuit layout, and then determining the optimal oil cooling system structure; Step 8: For the determined optimal oil cooling system structure, a three-dimensional thermal analysis model is used to simulate the stator temperature distribution cloud map under different typical working conditions, and the distribution areas corresponding to the highest temperatures of the winding and stator core are determined, which are used as the basis for subsequent motor cooling system optimization; Step 9. Build a high-speed flat-wire permanent magnet drive test motor entity based on the optimal oil cooling system structure, and build a motor temperature rise test platform based on the test motor entity; drive the test motor entity to operate under rated conditions and peak conditions through the test platform, and measure the temperature rise of the end winding and stator core at the same time, so as to verify the effect of the designed optimal oil cooling system structure.

2. The method according to claim 1, characterized in that: In step one, Motor CAD software is used to establish a two-dimensional electromagnetic field model of the motor, and Solid Works software is used to establish a three-dimensional structural model of the motor.

3. The method according to claim 1, characterized in that: In step 2, an oil circuit layout consisting of an oil inlet pipeline, two spray rings, a stator core oil circuit and an oil outlet pipeline is specifically designed; wherein the spray rings are arranged at both ends of the casing, and the stator core is located between the two spray rings; after the cooling oil flows from the outside of the casing into the inside through the oil pipeline, part of it is distributed to a spray ring, and is sprayed out from the spray holes distributed circumferentially on the spray ring under the action of oil pressure, so that the end winding on one side close to it is cooled; the other part of the cooling oil flows through the stator core oil circuit to another spray ring, and the stator core and the other side end winding are cooled during the flow process; the cooling oil after cooling flows out of the casing through the oil outlet pipeline and enters the next cooling cycle.

4. The method according to claim 1, characterized in that: The motor electromagnetic loss model established in step 3 specifically includes: Winding loss model: P Cu =P DC +P AC Where P Cu is the total winding loss, P DC is the DC loss of the winding; P AC is the winding AC loss; Among them, the DC loss P DC Calculated using the following formula: P DC =mI 2 R DC In the formula, m is the number of phases of the motor, I is the effective value of the motor phase current, R DC is the DC resistance of the winding, which is specifically expressed as: In the formula, l Cu is the average half-turn length of the winding, N Φ is the number of series turns per phase, σ Cu is the conductivity of copper, N is the number of parallel branches, and S is the cross-sectional area of ​​the winding; AC loss P AC Calculated using the following formula: In the formula, k s is the AC loss coefficient, B is the magnetic flux density, ω is the electrical angular frequency, d is the conductor thickness, W is the flat wire width, and l is the conductor length; Core loss model: Where P ir is the core loss, P h is the hysteresis loss, P e is the eddy current loss, P ex is the additional loss, K h and ɑ are the hysteresis loss coefficients, K e is the eddy current loss coefficient, K ex is the additional loss coefficient, B m is the peak value of magnetic flux density, f is the repetitive magnetization frequency; Permanent magnet eddy current loss model: Where P PM is the eddy current loss of permanent magnet, L a is the axial length of the permanent magnet, L b is the average width of the permanent magnet, V is the volume of the permanent magnet, ρ pm is the permanent magnet resistivity, K pm is the permanent magnet eddy current loss coefficient, f pm is the magnetic field alternating frequency, B pm is the maximum magnetic flux density of the permanent magnet.

5. The method according to claim 1, characterized in that: In step five, the motor fluid domain model is extracted using Ansys Space Claim software, and a three-dimensional thermal analysis model is established using Ansys Fluent software.

6. The method according to claim 1, characterized in that: In the simulation of step six, the maximum temperature of 180°C allowed by the motor insulation grade H is used as the threshold of the steady-state average temperature of the winding, and when the determined optimal injection ring specification exceeds this threshold, the core oil circuit simulation optimization of step seven is performed.

7. The method according to claim 1, characterized in that: The core oil circuit layout selected in step seven includes: a layout in which multiple axially extending straight oil circuits are evenly arranged outside the stator core, and various staggered oil circuit layouts including straight oil circuits, and the cross-sectional shape and size specifications at each position of the oil circuit are set.

8. The method according to claim 1, characterized in that: In step nine, a motor temperature rise test platform consisting of a test motor entity, a dynamometer, a controller, a thermometer, a power analyzer, and a constant temperature oil tank is specifically constructed; wherein, the controller is used to drive and control the operation of the test motor entity; the test motor entity is connected to the dynamometer through a coupling, and various motor operating conditions are loaded through the dynamometer; thermocouples connected to the thermometer are provided at the end windings and stator core slots of the test motor entity to measure the temperature rise at the corresponding positions; the power analyzer is used to measure the motor power and speed under various working conditions; the constant temperature oil tank is connected to the oil cooling system in the test motor entity and provides cooling oil circulation for it.

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