Motor temperature prediction method

Abstract

The technical scheme of the invention provides a motor temperature prediction method. The motor temperature prediction method comprises an electromagnetic thermal simulation step and a fluid heat exchange simulation step. In the electromagnetic thermal simulation step, the thermal loss of the motor is calculated by applying the temperature field distribution obtained in the fluid heat exchange simulation step; in the fluid heat exchange simulation step, the heat loss obtained in the electromagnetic heat simulation step is used as heat source input, and the overall temperature field distribution of the motor is calculated; the electromagnetic thermal simulation step and the fluid heat exchange simulation step are alternately and iteratively executed until a set termination condition is met. According to the motor temperature prediction method, temperature field simulation and heat loss updating of the motor are completed through the two steps of electromagnetic heat simulation and fluid heat exchange simulation which are executed in a coupling iteration mode, and temperature distribution of a stator and a rotor of the motor under different working conditions and pressure losses of the water-cooled motor in different water jacket shells can be accurately predicted; and the heat dissipation design of the motor is effectively optimized.

Description

Technical Field

[0001] The present application relates to the technical field of motor temperature simulation, and in particular to a method for predicting motor temperature. Background Art

[0002] In recent years, China's new energy vehicle industry has developed rapidly. As one of the core three-electric systems in new energy vehicles, the electric drive system is also undergoing rapid technological development. As the power source for vehicles of varying price points, electric drive systems are typically segmented by power to accommodate various vehicle models. Currently, due to the abundance of rare earth resources in China, the mainstream drive motor technology in China is the permanent magnet synchronous motor.

[0003] Permanent magnet synchronous motors are typically cooled by air or liquid. Air cooling is categorized into natural air cooling and forced fan cooling, while liquid cooling is generally divided into indirect water jacket cooling and direct oil cooling. Water jacket cooling offers the advantages of relatively high heat dissipation efficiency and low cost, making it widely used in low- and mid-range pure electric and hybrid passenger vehicles, commercial vehicles, and construction machinery.

[0004] During the R&D and design phase of water-cooled motors, different water jackets are typically designed to cool the motor's stator and rotor. Accurately evaluating the cooling effectiveness of different water jackets presents a challenge for motor designers. Furthermore, with competition in the new energy sector becoming increasingly fierce, meeting the heat dissipation requirements of water-cooled motors while maintaining low costs is a pressing technical challenge for the electric drive industry. Summary of the Invention

[0005] In view of the need to timely and effectively evaluate the heat dissipation capacity of a motor during the motor design process, the present application provides a motor temperature prediction method.

[0006] The present application provides a motor temperature prediction method, comprising an electromagnetic heat simulation step and a fluid heat exchange simulation step; The electromagnetic heat simulation step uses the temperature field distribution obtained in the fluid heat exchange simulation step to calculate the heat loss of the motor; The fluid heat exchange simulation step uses the heat loss obtained in the electromagnetic heat simulation step as a heat source input to calculate the temperature field distribution of the entire motor; The electromagnetic heat simulation step and the fluid heat exchange simulation step are alternately and iteratively executed until a set termination condition is reached.

[0007] Preferably, the simulation model in the fluid heat exchange simulation step includes a motor housing and a cooling fluid domain formed inside the motor housing; The stator assembly is formed inside the motor housing, including a stator core and a copper wire winding wound on the stator core; In addition, a rotating rotor assembly is provided coaxially with the stator assembly, which includes a rotor shaft, a rotor core and rotor magnets.

[0008] Preferably, in the fluid heat exchange simulation step, the copper wire winding is a calculation domain of a single material, and the equivalent specific heat capacity of the copper wire winding is for:

[0009] in, is the actual copper volume used in the motor design, is the volume of the copper wire winding in the simulation model, is the specific heat capacity of pure copper material, is the empirical coefficient.

[0010] Preferably, the thermal conductivity coefficients of the stator core and the rotor core are respectively set in the radial direction and the axial direction.

[0011] Preferably, in the simulation model of the fluid heat exchange simulation step, the middle section of the copper wire winding is in direct contact with the stator core, and the equivalent thermal resistance between the middle section of the copper wire winding and the stator core is set.

[0012] Preferably, the simulation model in the fluid heat exchange simulation step has an air rotation domain surrounding the rotor assembly.

[0013] Preferably, in the simulation model in the fluid heat exchange simulation step, the air rotation domain and the rotor assembly are both provided with rotating grids around the central axis.

[0014] Preferably, the cooling fluid domain inlet is a velocity inlet or a mass flow inlet, and the cooling fluid domain outlet is a pressure outlet.

[0015] Preferably, the turbulence simulation model in the fluid heat exchange simulation step selects a standard KE model, and the turbulence model and energy are calculated simultaneously; Alternatively, when the fluid heat exchange simulation step applies the heat loss obtained in the electromagnetic heat simulation step, each loss data obtained in the electromagnetic heat simulation step is assigned to the corresponding calculation domain in the form of a volume heat source.

[0016] Preferably, the termination condition is that the motor temperature field fluctuation is less than 0.1° C. during a single iterative calculation; or that the temperature field fluctuation is less than 1° C. after several iterative calculations.

[0017] This motor temperature prediction method uses a two-step, iterative coupling of electromagnetic thermal simulation and fluid heat transfer simulation to simulate the motor's temperature field and update heat loss. This coupled heat loss and temperature field calculations accurately predict the temperature distribution of the motor's stator and rotor under different operating conditions, as well as the pressure loss of water-cooled motors under different water jacket conditions, effectively optimizing the motor's heat dissipation design. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] Figure 1 This is a schematic diagram of the key process of the motor temperature prediction method of this application; Figure 2 A schematic diagram of the simulation process of the motor temperature prediction method of this application; Figure 3 A cross section of a motor simulation model for the motor temperature prediction method of this application; Figure 4 A schematic diagram of a cooling fluid domain 1 of the motor temperature prediction method of the present application; Figure 5 Setting parameters for the physical model in the fluid heat exchange step of the motor temperature prediction method of the present application; Figure 6 This is the material parameter setting for each calculation domain of the motor temperature prediction method of this application.

[0019] In the picture: 1: Cooling fluid domain; 2: Static air domain; 3: Rotating air domain; 4: Rotor shaft; 5: Copper wire winding; 6: Stator core; 7: Rotor core; 8: Rotor magnets; 9: Motor housing. DETAILED DESCRIPTION

[0020] The following is a detailed description of the technical solution of the present application in conjunction with the accompanying drawings and specific embodiments. In this specification, the dimensions of the drawings do not represent the actual size ratios. The drawings are only used to reflect the relative position relationship and connection relationship between the various components. Components with the same name or the same number represent similar or identical structures and are only for illustrative purposes.

[0021] Figure 1This is a schematic diagram of the key process flow of the motor temperature prediction method of the present application, which includes two steps: electromagnetic thermal simulation and fluid heat exchange simulation. In the electromagnetic thermal simulation step, the temperature field distribution obtained from the fluid heat exchange simulation is input. Through electromagnetic thermal simulation, the heat loss of the motor is obtained under the corresponding electromagnetic system conditions, which is the heat source input in the fluid heat exchange simulation. At the same time, in the fluid exchange simulation step, the heat loss obtained from the electromagnetic thermal simulation is used as the heat source input. Under the corresponding boundary conditions and other physical parameters of the model, the temperature field distribution of the entire motor is obtained. This coupled process is iterated alternately until the output reaches the set termination condition. After the iterative process terminates, the corresponding temperature field distribution is checked, which is the simulated temperature distribution of the motor during steady-state operation, and the corresponding heat loss data is the heat loss data of each component of the motor under steady-state operation. Optional iterative termination conditions are that the temperature values ​​of each motor component tend to be stable during a single iterative calculation, and the numerical fluctuation should be less than 0.1°C; or that after multiple rounds of iterative calculations, the difference in the numerical results of the temperature simulation calculations of the corresponding components of the motor at multiple positions is less than 1°C, or the above conditions are met at the same time.

[0022] The motor temperature prediction method is mainly divided into three parts: simulation pre-processing, simulation calculation and calculation result post-processing. The simulation process is as follows Figure 2 shown.

[0023] Specifically, for fluid heat transfer simulation, the first step is to prepare a simulation model. This model is obtained by simplifying the actual 3D motor model. This simplification involves removing fillets and small surface features from the digital model of the water-cooled motor structure that don't affect heat transfer analysis.

[0024] For water-cooled motors, the main structures are the water-cooling casing, the rotor assembly (including the rotating shaft, silicon steel sheets and permanent magnets), and the stator assembly (copper wire windings, silicon steel sheets). For the stator core part, the structural digital model characteristics are retained, the insulating paper between the winding and the core and the insulating layer on the surface of the copper wire are ignored, and the middle section of the copper wire winding is regarded as in direct contact with the stator core. The equivalent thermal resistance parameters between the two are established through benchmarking-experiments to equate the insulating paper and other structures, thereby reducing the difficulty of modeling. For the rotor assembly part, the rotor core is simplified, the slots around the core are ignored, and the minimum gap between the rotor core and the stator core is controlled to be above 1.2mm, thereby establishing an air rotation domain structure that wraps the rotor assembly, and the air domain within the holes of the rotor assembly core is retained. For the water jacket shell of the water-cooled motor, on the one hand, the small local features on the water jacket shell need to be simplified, and on the other hand, the cooling medium fluid domain inside the water jacket shell needs to be established. In the patent of this invention, a certain model of water-cooled motor in the project development process is taken as an example. The cooling fluid domain 1 in the axially stretched water jacket shell of this product is as follows: Figure 4 shown.

[0025] Copper wire windings are commonly categorized into round and flat wire types. For flat wire windings, ensuring no interference between the copper wires is sufficient. For round wire windings, based on empirical methods, they are divided into three sections: the outgoing end, the non-outgoing end, and the mid-winding. During simulation pre-processing, the copper wire windings are simplified, ignoring the effects of the copper wire insulation layer and the varnishing process. Slots around the core are ignored, and the minimum gap between the rotor and stator cores is controlled to at least 1.2 mm. This creates a rotating air domain that encloses the rotor assembly, while preserving the air domain within the rotor core cavities.

[0026] The final cross-sectional diagram of the motor simulation model is as follows: Figure 3 , which includes a motor housing 9 and a cooling fluid domain 1 formed inside the motor housing 9. A stator assembly is formed inside the motor housing 9, including a stator core 6 and a copper wire winding 5 wound on the stator core 6. In addition, there is a rotating rotor assembly coaxially arranged with the stator assembly, which includes a rotor shaft 4, a rotor core 7 and a rotor magnet 8. A thin layer of air rotating domain 3 is additionally provided on the periphery of the rotor assembly. The provision of the air rotating domain 3 ensures that the minimum gap between the rotor core and the stator core is controlled to be above 1.2 mm. The space inside the motor housing 9 except the air rotating domain 3 is an air static domain 2.

[0027] The pre-processed water-cooled motor simulation model is imported into simulation software such as STAR CCM+ as an X_T or STP file. The software then meshes the solid and fluid regions separately. Rotating meshes are set for the stator core 6, rotor core 7, rotor magnets 8, and the air rotating domain 3 surrounding the rotor assembly. The rotational motion is set to align with actual operating conditions, i.e., rotation around the central axis while maintaining a speed consistent with actual operating conditions.

[0028] Next, the physical properties of each computational domain must be determined. In this application's simulation model, the copper wire winding 5 is simplified, ignoring the effects of the copper wire insulation layer and the varnishing process. This actually affects the heat transfer characteristics of this area, necessitating compensation for the heat transfer characteristics of the copper wire winding 5. Therefore, to correct for the material specific heat capacity of the copper wire winding 5 in this patent, an empirical formula is proposed, as shown below.

[0029]

[0030] In the formula, is the actual copper volume used in the motor design, is the volume of the copper wire winding in the simulation model, is the specific heat capacity of pure copper material, is the empirical coefficient. That is the corrected material specific heat capacity of the copper wire winding 5 used for simulation calculation.

[0031] For the boundary conditions, for the cooling fluid domain 1, the water channel inlet can use either a velocity inlet or a mass flow inlet, and the water channel outlet is set as a pressure outlet. For the air rotation domain 3, the rotation domain speed is set by establishing a local reference coordinate system (the speed is consistent with the actual working conditions); the equivalent contact thermal resistance of the contact surface between the mid-section winding and the stator core is set based on empirical data.

[0032] Next is the simulation calculation parameter setting, which mainly includes physical model selection, calculation domain material property parameter setting and water-cooled motor heat loss parameter setting. Figure 5 As shown, in the present invention, the coolant flow in the cooling fluid domain 1 is regarded as a single-phase turbulent flow, and the standard KE model is selected as the turbulence simulation model. The turbulence model and energy are calculated simultaneously. The stator and rotor cores are regarded as anisotropic thermal conductive materials due to the processing technology. The radial and axial thermal conductivity coefficients are set separately, and the middle section winding is also anisotropic material. The specific material parameter settings are as follows Figure 6 .

[0033] During the simulation of the above model, the heat source settings are provided by the electromagnetic heat simulation step. Specifically, the electromagnetic heat simulation step obtains the motor's copper losses (heat loss of the copper winding 5), iron losses (heat loss of the stator core 6 and rotor core 7), and magnetic steel losses (heat loss of the rotor magnetic steel 8). Mechanical losses are optionally included. The loss data obtained in the electromagnetic heat simulation step is assigned to the corresponding computational domain via a volumetric heat source.

[0034] The present invention couples thermal simulation software with electromagnetic design software to form a magnetothermal coupling simulation. The motor temperature field results are fed back to the electromagnetic design software to correct the electromagnetic calculation loss. This cycle continues until the temperature field calculation results of the water-cooled motor stabilize. During the electromagnetic thermal simulation process, the temperature field in each conductor domain is averaged by the components and used in the electromagnetic simulation to obtain the heat loss of each component in the electromagnetic simulation model at that temperature. Optionally, the electromagnetic thermal simulation can be based on a 3D model simulation or a 2D model simulation.

[0035] The main structures of a water-cooled motor are the water-cooling jacket, the rotor assembly (including the rotating shaft, silicon steel sheets, and permanent magnets), and the stator assembly (copper wire windings, silicon steel sheets). The losses generated by a water-cooled motor during operation are mainly divided into: heat loss of the copper wire windings, heat loss of the stator and rotor cores, heat loss of the magnetic steel, as well as mechanical loss and wind friction loss. Based on the law of conservation of energy, these losses will eventually manifest as heat causing the various components of the water-cooled motor to heat up. The technical solution of this application uses ALTAIRFLUX software to simulate and calculate the loss values ​​of the water-cooled motor under different operating conditions.

[0036] The STAR CCM+ software's built-in post-processing capabilities enable the determination of the temperature distribution of the motor's stator and rotor assembly, the pressure distribution in the water jacket fluid domain, and the velocity vector streamlines. These post-processing results can be used to determine whether the motor is at risk of overheating under the specified operating conditions and whether the water channel pressure drop meets the requirements of the vehicle's thermal management system. This patent uses a water-cooled motor operating continuously at 8650 rpm as an example. Bench testing verified that the simulated maximum stator temperature deviated from the experimental result by 5.3%.

[0037] The advantage of the motor temperature prediction method of the present application is that, while considering the thermal coupling between multiple heat-generating components inside the motor, it can accurately predict the temperature distribution of the stator and rotor of the water-cooled motor under different working conditions and the pressure loss of different water jackets, thereby effectively optimizing the heat dissipation design of the water-cooled motor.

[0038] The above content only describes the preferred implementation mode of the present application and does not limit the scope of the present application. Without departing from the design spirit of the present application, various modifications and improvements made to the technical solution of the present application by ordinary technicians in this field should fall within the scope of protection determined by the claims of the present application.

Claims

1. A method for predicting motor temperature, characterized in that: It includes electromagnetic heat simulation steps and fluid heat exchange simulation steps; The electromagnetic heat simulation step uses the temperature field distribution obtained in the fluid heat exchange simulation step to calculate the heat loss of the motor; The fluid heat exchange simulation step uses the heat loss obtained in the electromagnetic heat simulation step as a heat source input to calculate the temperature field distribution of the entire motor; The electromagnetic heat simulation step and the fluid heat exchange simulation step are executed alternately and iteratively until a set termination condition is reached.

2. The motor temperature prediction method according to claim 1, characterized in that: The simulation model in the fluid heat exchange simulation step includes a motor housing (9) and a cooling fluid domain (1) formed inside the motor housing (9); A stator assembly is formed inside the motor housing (9), comprising a stator core (6) and a copper wire winding (5) wound on the stator core (6); In addition, there is a rotating rotor assembly coaxially arranged with the stator assembly, which comprises a rotor shaft (4), a rotor core (7) and a rotor magnet (8).

3. The motor temperature prediction method according to claim 2, characterized in that: In the fluid heat exchange simulation step, the copper wire winding (5) is a calculation domain of a single material, and the equivalent specific heat capacity of the copper wire winding (5) is for: in, is the actual copper volume used in the motor design, is the volume of the copper wire winding in the simulation model, is the specific heat capacity of pure copper material, is the empirical coefficient.

4. The motor temperature prediction method according to claim 2, characterized in that: The thermal conductivity coefficients of the stator iron core (6) and the rotor iron core (7) are respectively set in the radial direction and the axial direction.

5. The motor temperature prediction method according to claim 2, characterized in that: In the simulation model of the fluid heat exchange simulation step, the middle winding of the copper wire winding (5) is in direct contact with the stator core (6), and the equivalent thermal resistance between the middle winding of the copper wire winding (5) and the stator core (6) is set.

6. The motor temperature prediction method according to claim 2, characterized in that: The simulation model in the fluid heat exchange simulation step has an air rotation domain (3) surrounding the rotor assembly.

7. The motor temperature prediction method according to claim 6, characterized in that: In the simulation model in the fluid heat exchange simulation step, the air rotation domain (3) and the rotor assembly are both provided with a rotating grid around a central axis.

8. The motor temperature prediction method according to claim 2, characterized in that: The inlet of the cooling fluid domain (1) is a velocity inlet or a mass flow inlet, and the outlet of the cooling fluid domain (1) is a pressure outlet.

9. The motor temperature prediction method according to claim 2, characterized in that: The turbulence simulation model in the fluid heat exchange simulation step selects the standard KE model, and the turbulence model and energy are calculated simultaneously; Alternatively, when the fluid heat exchange simulation step applies the heat loss obtained in the electromagnetic heat simulation step, each loss data obtained in the electromagnetic heat simulation step is assigned to the corresponding calculation domain in the form of a volume heat source.

10. The motor temperature prediction method according to claim 1, characterized in that: The termination condition is that the motor temperature field fluctuation is less than 0.1°C during a single iterative calculation; or that the temperature field fluctuation is less than 1°C after several iterative calculations.

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