Copper-aluminum composite busbar, design method thereof, motor control system and vehicle

Abstract

The application discloses a copper-aluminum composite busbar, a design method thereof, a motor control system and a vehicle. The copper-aluminum composite busbar is composed of a first copper plate in an upper layer, an aluminum plate in a middle layer and a second copper plate in a lower layer. The thickness of the first copper plate and the thickness of the second copper plate in the bolt lap joint area of the copper-aluminum composite busbar are greater than the thickness of the first copper plate and the thickness of the second copper plate in the non-lap joint area of the copper-aluminum composite busbar. The thickness of the aluminum plate corresponding to the bolt lap joint area of the copper-aluminum composite busbar is less than the thickness of the aluminum plate in the non-lap joint area of the copper-aluminum composite busbar. The differentiated matching design of thickening the copper plate and thinning the aluminum plate in the bolt lap joint area can reduce the generation of joule heat in the bolt lap joint area, optimize the temperature rise distribution of the copper-aluminum composite busbar and improve the performance of the copper-aluminum composite busbar.

Description

Technical Field

[0001] This invention belongs to the field of components of motor control systems, specifically relating to a copper-aluminum composite busbar and its design method, a motor control system, and a vehicle. Background Technology

[0002] With the continuous increase in power density of new energy vehicles and industrial drive systems, higher requirements are being placed on the three-phase AC busbars (hereinafter referred to as busbars) that carry and distribute electrical energy. Three-phase AC busbars are mostly made of pure copper and connected to power module (such as IGBT / SiC) terminals and motor terminals via bolts. Although pure copper busbars have excellent conductivity, the high cost and weight of copper limit further cost and weight reduction. To balance cost and performance, a copper-aluminum composite busbar solution is currently adopted. The copper-aluminum composite busbar consists of a first copper plate on top, an aluminum plate in the middle, and a second copper plate at the bottom. The first and second copper plates have the same structure, i.e., the upper and lower surfaces are made of copper while the middle is made of aluminum, thereby reducing component cost and weight. The thicknesses of the first, aluminum, and second copper plates in the copper-aluminum composite busbar are determined according to a standard proportional relationship.

[0003] However, in practical applications, especially under three-phase AC conditions, existing copper-aluminum composite busbars have two prominent problems:

[0004] First, contact resistance. Due to the uneven roughness of the contact surfaces in the bolt lap area (also known as the bolt lap surface) between the first copper plate, the second copper plate and the external terminal, contact resistance will inevitably occur. The contact resistance will cause the local temperature rise in this lap area to be significantly higher than that in other parts of the busbar, thus forming hot spots and affecting the overall current carrying capacity and system reliability of the copper-aluminum composite busbar.

[0005] Second, the skin effect. High-frequency alternating current causes current to concentrate on the conductor surface. For copper-aluminum composite busbars, the current tends to concentrate on the copper plate surface. However, the existing copper-aluminum composite busbar structure and copper plate thickness basically do not take into account the influence of the skin effect.

[0006] Therefore, existing copper-aluminum composite busbars fail to fully consider the non-uniform temperature rise caused by contact resistance and skin effect, resulting in the inability to fully utilize the performance of copper-aluminum composite busbars, which becomes a bottleneck restricting the maximization of current output capability of copper-aluminum composite busbars. Summary of the Invention

[0007] In view of the shortcomings of the prior art, the purpose of this application is to provide a copper-aluminum composite busbar and its design method, motor control system, and vehicle, so as to optimize the temperature rise distribution and improve the performance of the copper-aluminum composite busbar.

[0008] In one aspect, this application provides a copper-aluminum composite busbar, comprising a first copper plate in the upper layer, an aluminum plate in the middle layer, and a second copper plate in the lower layer. The thicknesses of the first and second copper plates in the bolt lap area of ​​the copper-aluminum composite busbar are greater than those in the non-lap area, and the thickness of the aluminum plate corresponding to the bolt lap area is less than that in the non-lap area. By employing a differentiated design with thicker copper plates and thinner aluminum plates in the bolt lap area, the low resistivity, high temperature resistance, and high contact stability of the copper plate are utilized to compensate for contact resistance loss in the bolt lap area, reducing Joule heat generation in the bolt lap area, optimizing the temperature rise distribution of the copper-aluminum composite busbar, and improving its performance, thereby significantly improving the reliability and efficiency of the system.

[0009] Optionally, the thickness of the first copper plate and the thickness of the second copper plate in the non-lap area of ​​the copper-aluminum composite busbar are equal to the skin depth of the first copper plate and the second copper plate at f. Where f represents the inverter switching frequency of the copper-aluminum composite busbar under actual application conditions. The skin depth at f is directly used as the thickness of the first and second copper plates in the non-lap area of ​​the copper-aluminum composite busbar. This ensures that the thicknesses of the first and second copper plates accurately match the current skin effect distribution under high-frequency operating conditions, fully utilizing the high conductivity of copper plates. Under the premise of meeting high-frequency current carrying requirements, the amount of copper material used is minimized, achieving the optimal match between material cost and conductivity efficiency.

[0010] Optionally, the thickness of the aluminum plate in the non-overlapping area of ​​the copper-aluminum composite busbar is less than or equal to a preset aluminum plate cost constraint thickness, and satisfies: at an ambient temperature of T max The operating current is I max Under normal operating conditions, the maximum temperature of the copper-aluminum composite busbar is lower than or equal to the maximum allowable operating temperature of the copper-aluminum composite busbar for the electric drive; where T max Indicates the maximum operating ambient temperature of the copper-aluminum composite busbar, I max This indicates the rated current of the input motor. By controlling the thickness of the aluminum plate in the non-overlapping area within a cost-constrained range, the amount of aluminum material used can be effectively reduced, thus lowering the overall material production cost of the copper-aluminum composite busbar. The maximum operating ambient temperature T is used as the reference. max Input motor rated current I max Conducting thermal performance verification under extreme conditions comprehensively verifies the heat accumulation and heat dissipation capabilities under high-current full-load operation. Strictly limiting the maximum operating temperature of the copper-aluminum composite busbar to below or equal to the allowable limit temperature of the electric drive under extreme conditions ensures that the copper-aluminum composite busbar will not experience overheating or over-temperature phenomena in high-temperature environments and under full-load operation, effectively avoiding safety hazards such as insulation aging, electrical performance degradation, and structural deformation caused by excessive temperature rise.

[0011] Optionally, the thickness of the first copper plate and the thickness of the second copper plate in the bolt lap area of ​​the copper-aluminum composite busbar are less than or equal to a preset copper plate cost constraint thickness, and satisfy the following condition: at an ambient temperature of T... max The operating current is I max Under certain operating conditions, the temperature difference between the bolt lap area and the non-lap area of ​​the copper-aluminum composite busbar is less than a preset temperature difference threshold. Setting an upper limit constraint on the thickness of the first and second copper plates in the bolt lap area of ​​the copper-aluminum composite busbar, ensuring they do not exceed a preset copper plate cost constraint thickness, effectively controls the use of precious copper materials, reduces raw material input, and lowers the overall manufacturing cost of the busbar. (Based on the highest operating ambient temperature T...) max Input motor rated current I max As a verification condition, the temperature difference between the overlapping area and the non-overlapping area is limited to less than the preset temperature difference threshold. This can effectively balance the heat distribution in different areas of the busbar and avoid local abnormal heat accumulation at the bolt overlap due to high contact resistance and concentrated current.

[0012] Optionally, the thickness of the aluminum plate corresponding to the bolt lap area of ​​the copper-aluminum composite busbar is less than or equal to a preset aluminum plate cost constraint thickness, and satisfies: at an ambient temperature of T max The operating current is I max Under certain operating conditions, the temperature difference between the bolt lap area and the non-lap area of ​​the copper-aluminum composite busbar is less than a preset temperature difference threshold. Limiting the aluminum plate thickness corresponding to the bolt lap area of ​​the copper-aluminum composite busbar to a preset aluminum plate cost constraint thickness can effectively reduce the amount of aluminum material used and lower the overall material production cost of the copper-aluminum composite busbar. (Based on the highest operating ambient temperature T...) max Input motor rated current I max As a verification condition, the temperature difference between the overlapping area and the non-overlapping area is limited to less than the preset temperature difference threshold. This can effectively balance the heat distribution in different areas of the busbar and avoid local abnormal heat accumulation at the bolt overlap due to high contact resistance and concentrated current.

[0013] Secondly, this application provides a design method for the aforementioned copper-aluminum composite busbar, comprising:

[0014] Obtain the inverter switching frequency f and the maximum operating ambient temperature T of the copper-aluminum composite busbar under actual application conditions. max Input motor rated current I max .

[0015] Calculate the skin depth of the first and second copper plates at the inverter switching frequency f. .

[0016] The skin depth As the base thickness of the first copper plate and the base thickness of the second copper plate.

[0017] Set the ambient temperature to T. max Continuous loading current I max The thickness of the aluminum plate foundation was determined by finite element iterative simulation of the copper-aluminum composite busbar.

[0018] The thickness of the first copper plate base, the thickness of the aluminum plate base, and the thickness of the second copper plate base are respectively used as the thickness of the first copper plate, the thickness of the aluminum plate, and the thickness of the second copper plate in the non-overlapping area of ​​the final copper-aluminum composite busbar.

[0019] Calculate the contact resistance of the bolt lap joint area .

[0020] Import the contact resistance Set the ambient temperature to T max Continuous loading current I max By using finite element iterative simulation of copper-aluminum composite busbars with thickened copper plates and thinned aluminum plates in the bolt lap area, the thicknesses of the first and second copper plates and the corresponding aluminum plates in the bolt lap area of ​​the final copper-aluminum composite busbar were determined.

[0021] The skin depth is calculated based on the actual switching frequency f of the inverter, and directly used as the base thickness of the first and second copper plates. This ensures that the thicknesses of the first and second copper plates accurately match the current skin effect distribution under high-frequency operating conditions, fully utilizing the high conductivity of copper plates. While meeting high-frequency current carrying requirements, the amount of copper material used is minimized, achieving an optimal balance between material cost and conductivity efficiency. This is based on the highest operating ambient temperature T. max Input motor rated current I max Using finite element iterative simulation as boundary conditions, the thickness of the aluminum plate foundation is determined. This allows for the quantitative simulation of the busbar temperature rise, heat distribution, and current-carrying characteristics under actual extreme working conditions. It precisely matches the conductivity, heat dissipation, and structural load-bearing requirements of the aluminum plate, ensuring that the non-lapped area maintains compliant temperature rise, stable current carrying capacity, and no risk of overheating failure under extreme conditions. This enables the scientific and quantitative design of the structural parameters of the non-lapped area. The contact resistance of the bolt lapped area is pre-calculated and imported into the simulation model, accurately reproducing the actual electrical contact characteristics of the bolt lapped area, improving the accuracy and engineering applicability of the bolt lapped area structural design. A differentiated design with thicker copper plates and thinner aluminum plates is adopted for the bolt lapped area. The low resistivity, high temperature resistance, and high contact stability of the copper plate compensate for the contact resistance loss in the bolt lapped area, reducing Joule heat generation and optimizing the temperature rise distribution of the copper-aluminum composite busbar. This improves the performance of the copper-aluminum composite busbar, thereby significantly enhancing the system's reliability and efficiency.

[0022] Optionally, the aluminum plate foundation thickness is determined as follows: based on the first copper plate foundation thickness, the second copper plate foundation thickness, and the preset initial aluminum plate thickness, a first simulation model is built; wherein, the first simulation model is a copper-aluminum composite busbar finite element simulation model. The ambient temperature is set to T.max Continuous loading current I max Starting from a preset initial aluminum plate thickness (i.e., using the preset initial aluminum plate thickness as the initial adjustment value), the aluminum plate thickness is gradually increased, and iterative simulations are performed until the highest temperature of the copper-aluminum composite busbar in the first simulation model is lower than or equal to the highest operating temperature of the copper-aluminum composite busbar allowed by the electric drive. The aluminum plate thickness in the first simulation model at this point (i.e., when the highest temperature of the copper-aluminum composite busbar in the first simulation model is lower than or equal to the highest operating temperature of the copper-aluminum composite busbar allowed by the electric drive) is taken as the base aluminum plate thickness. The base aluminum plate thickness is the minimum aluminum plate thickness that satisfies the requirement that the highest temperature of the copper-aluminum composite busbar in the first simulation model be lower than or equal to the highest operating temperature of the copper-aluminum composite busbar allowed by the electric drive. A finite element simulation model of the copper-aluminum composite busbar is built by combining the first and second base copper plate thicknesses and the initial aluminum plate thickness, with T... max and I max To simulate boundary conditions, accurately reproduce extreme working conditions, ensure that the aluminum plate thickness meets the extreme usage requirements, avoid overheating failure and material waste, an iterative simulation method of gradually increasing aluminum plate thickness is adopted to accurately determine the minimum aluminum plate thickness that meets the temperature requirements, thereby reducing manufacturing costs.

[0023] Optionally, the skin depth of the first copper plate and the second copper plate at the inverter switching frequency f can be calculated as follows:

[0024] Using the formula: The skin depths of the first and second copper plates at the inverter switching frequency f were calculated. ;in, Indicates the magnetic permeability of copper, This indicates the electrical conductivity of copper. , Represents the permeability of free space. This represents the relative permeability of copper. The electrical conductivity of copper This is due to the inherent properties of copper; therefore, , The quantity is known.

[0025] By using the formula: And with the magnetic permeability of copper The electrical conductivity of copper The inverter switching frequency f is used as a calculation parameter to accurately determine the skin depth. This achieves a theoretically precise match between copper plate thickness and high-frequency skin effect, ensuring quantitative controllability of thickness design, effectively saving copper material usage and reducing costs. At the same time, it ensures that the copper-aluminum composite busbar has high current efficiency, uniform heating, and stable and reliable operation at the target switching frequency.

[0026] Optionally, the contact resistance of the bolt lap joint area can be calculated as follows:

[0027] Using the formula: The contact resistance of the bolt lap joint area was calculated. Where F represents the preset contact pressure of the bolt lap joint area, K represents the material and surface coefficient, and m represents the contact form index of the bolt lap joint area. K is obtained from a table based on the contact material, and m is obtained based on the contact point type of the bolt lap joint area.

[0028] By using the formula: The contact resistance of the bolt lap joint area is accurately determined using preset parameters such as the contact pressure F, material and surface coefficient K, and contact form index m of the bolt lap joint area. This enables the theoretical and precise calculation of contact resistance, improving the accuracy and reliability of the calculation results and providing a precise data foundation for subsequent simulation optimization of the bolt lap joint area.

[0029] Optionally, the method for determining the thickness of the first copper plate, the thickness of the second copper plate, and the corresponding thickness of the aluminum plate in the bolt lap area of ​​the final copper-aluminum composite busbar is as follows:

[0030] Select the bolt lap joint area, and build a second simulation model based on the thickness of the first copper plate base, the thickness of the second copper plate base, and the thickness of the aluminum plate base; wherein, the second simulation model is a finite element simulation model of a copper-aluminum composite busbar with thickened copper plate and thinned aluminum plate in the bolt lap joint area.

[0031] The contact resistance Import the second simulation model and set the ambient temperature to T. max Continuous loading current I max While keeping the total thickness of the copper-aluminum composite busbar constant, starting from the thickness of the first copper plate base, the thickness of the second copper plate base, and the thickness of the aluminum plate base (i.e., using the thickness of the first copper plate base, the thickness of the second copper plate base, and the thickness of the aluminum plate base as the initial values ​​for adjustment), the thickness of the first copper plate and the thickness of the second copper plate in the bolt lap area are gradually increased, and the thickness of the aluminum plate corresponding to the bolt lap area is gradually decreased accordingly. Iterative simulation is performed until the temperature difference between the bolt lap area and the non-lap area in the second simulation model is less than the preset temperature difference threshold.

[0032] The thicknesses of the first copper plate, the second copper plate, and the corresponding aluminum plate in the bolt lap area of ​​the second simulation model at this point (i.e., when the temperature difference between the bolt lap area and the non-lap area is less than a preset temperature difference threshold) are taken as the thicknesses of the first copper plate, the second copper plate, and the corresponding aluminum plate in the bolt lap area of ​​the final copper-aluminum composite busbar. The thicknesses of the first copper plate, the second copper plate, and the corresponding aluminum plate in the bolt lap area of ​​the final copper-aluminum composite busbar are the minimum first copper plate thickness, the minimum second copper plate thickness, and the maximum aluminum plate thickness required to satisfy the condition that the temperature difference between the bolt lap area and the non-lap area is less than a preset temperature difference threshold.

[0033] A finite element simulation model of a copper-aluminum composite busbar with thickened copper plates and thinned aluminum plates in the bolt lap area was constructed based on the thicknesses of the first copper plate foundation, the second copper plate foundation, and the aluminum plate foundation. This model achieves coordinated design between the bolt lap area thickness and the non-lap area foundation thickness. The previously calculated contact resistance was imported into the finite element simulation model of the copper-aluminum composite busbar with thickened copper plates and thinned aluminum plates in the bolt lap area, combined with T... max I max By setting precise boundary conditions, the electrical contact characteristics and extreme working scenarios of the bolt lap joint area in actual operation are accurately reproduced. This effectively avoids simulation distortion caused by neglecting contact resistance or deviations in operating condition settings, ensuring that the simulation results can truly reflect the temperature rise and current carrying characteristics of the bolt lap joint area, providing reliable data for thickness optimization. Using the thickness of each foundation as the initial value, while maintaining the total thickness of the copper-aluminum composite busbar unchanged, an iterative adjustment method is adopted to simultaneously thicken two layers of copper plates and correspondingly thin the aluminum plates. This avoids the impact of changes in the total thickness of the copper-aluminum composite busbar on the overall installation adaptability and structural stability. Furthermore, by thickening the first and second copper plates, the advantages of copper's low resistivity and high heat dissipation are fully utilized to compensate for the losses caused by the contact resistance in the bolt lap joint area. Using a temperature difference between the bolt lap area and the non-lap area that is less than a preset temperature difference threshold as the iteration termination condition, the temperature rise in the bolt lap area and the non-lap area can be made to be consistent, thus achieving a balanced temperature distribution of the copper-aluminum composite busbar. This effectively solves the problems of excessive heat generation and excessive temperature difference in the bolt lap area caused by contact resistance, avoids overheating failure in the bolt lap area, and ensures that the performance of the non-lap area is not affected. This ensures stable current carrying capacity and controllable heat generation throughout the copper-aluminum composite busbar, and improves the overall electrical reliability and service life of the copper-aluminum composite busbar.

[0034] Optionally, the thickness of the first copper plate and the second copper plate in the bolt lap joint area can be gradually increased by following a preset first gradient. The thickness of the first and second copper plates in the bolt lap area is gradually increased. The thickness of the aluminum plate corresponding to the bolt lap area is gradually decreased according to a preset second gradient. Gradually reduce the thickness of the aluminum plate corresponding to the bolt lap joint area; among which, Through the preset first gradient Gradually increase the thickness of the first and second copper plates in the bolt lap area, through a preset second gradient. Gradually reduce the corresponding aluminum plate thickness, and limit... While maintaining a constant total thickness of the copper-aluminum composite busbar, it not only achieves quantitative control and precise adaptation of the bolt lap joint thickness adjustment, avoiding damage to structural adaptability, but also improves the efficiency of iterative simulation by precisely controlling the thickness optimization rhythm through gradient adjustment.

[0035] Thirdly, this application provides a motor control system, which includes the aforementioned copper-aluminum composite busbar.

[0036] Fourthly, this application provides a vehicle that includes the aforementioned motor control system. Attached Figure Description

[0037] To more clearly illustrate the technical solutions in the embodiments of this application, the accompanying drawings used in the embodiments of this application will be described below.

[0038] Figure 1 This is a schematic diagram of the vehicle in an embodiment of this application;

[0039] Figure 2 This is a partial structural schematic diagram of the copper-aluminum composite busbar in an embodiment of this application;

[0040] Figure 3 This is a flowchart of the copper-aluminum composite busbar design method in the embodiments of this application;

[0041] Figure 4 This is a flowchart illustrating the method for determining the thickness of the aluminum plate base in this application embodiment;

[0042] Figure 5 This is a flowchart illustrating the method for determining the thickness of the first copper plate, the thickness of the second copper plate, and the corresponding thickness of the aluminum plate in the bolt lap area of ​​the final copper-aluminum composite busbar in this embodiment of the application.

[0043] In the diagram, 1 is the first copper plate, 2 is the aluminum plate, and 3 is the second copper plate. Detailed Implementation

[0044] The embodiments of this application will be described in further detail below with reference to the accompanying drawings and examples. The detailed description of the following embodiments and the accompanying drawings are used to illustrate the principles of this application by way of example, but should not be used to limit the scope of this application, that is, this application is not limited to the described embodiments.

[0045] like Figure 1 As shown, Figure 1This is a schematic diagram of a vehicle in an embodiment of this application. The vehicle may be, but is not limited to, a pure electric vehicle (PEV / BEV), a hybrid electric vehicle (HEV), a range-extended electric vehicle (REEV), a plug-in hybrid electric vehicle (PHEV), or a new energy vehicle.

[0046] In this embodiment, the vehicle includes a motor control system. The motor control system includes the copper-aluminum composite busbar as described in this embodiment.

[0047] This section provides a complete and detailed implementation description of the copper-aluminum composite busbar and its design method, based on the actual operating conditions of the 600V platform motor control system for new energy vehicles. As an example, the main drive motor controller of the new energy vehicle has a rated power of 250kW and a DC bus voltage of 600V.

[0048] like Figure 2 As shown in the embodiment of this application, the copper-aluminum composite busbar adopts a flat integrated structure, consisting of a first copper plate 1 on the upper layer, an aluminum plate 2 in the middle layer, and a second copper plate 3 on the lower layer. The first copper plate 1 and the second copper plate 3 have the same structure and dimensions. The bolt lap area of ​​the copper-aluminum composite busbar (see...) Figure 2 The thickness of the first copper plate and the thickness of the second copper plate in the right-hand area are greater than the thickness of the non-lapped area of ​​the copper-aluminum composite busbar (see [reference]). Figure 2The thickness of the first copper plate and the thickness of the second copper plate in other areas of the copper-aluminum composite busbar are specified. The thickness of the aluminum plate corresponding to the bolt lap area is less than the thickness of the aluminum plate in the non-lap area of ​​the copper-aluminum composite busbar. As a critical node for current transmission, the bolt lap area has significant contact resistance, generating additional Joule heat and forming localized hot spots, threatening the reliability of the copper-aluminum composite busbar and the system. Therefore, targeted structural optimization of the bolt lap area is required: extending 10mm outward from the center of the M8 bolt hole as the effective lap area, and performing structural adjustments to thicken the copper plate and thin the aluminum plate within this effective lap area to reduce the maximum temperature of the bolt lap area. The bolt lap area structure can be rectangular, triangular, trapezoidal, or other shapes that allow for localized thickening. In this embodiment, a rectangular localized thickening is selected. As an example, the thickened structure in the overlap area can be formed using a semi-molten rolling composite process. The copper-aluminum bonding surface is roughened by sandblasting (Ra=2.0μm) to effectively remove the oxide layer and impurities, improve the bonding interface strength, and achieve a bonding strength ≥160MPa. Process verification shows no risk of delamination or cracking, ensuring the structural stability for long-term operation.

[0049] In one possible embodiment, the thickness of the first copper plate and the thickness of the second copper plate in the non-lapped area of ​​the copper-aluminum composite busbar are equal to the skin depth of the first copper plate 1 and the second copper plate 3 under f. Where f represents the inverter switching frequency of the copper-aluminum composite busbar under actual application conditions. The skin depth at f is directly used as the thickness of the first and second copper plates in the non-lap area of ​​the copper-aluminum composite busbar. This ensures that the thicknesses of the first and second copper plates accurately match the current skin effect distribution under high-frequency operating conditions, fully utilizing the high conductivity of copper plates. Under the premise of meeting high-frequency current carrying requirements, the amount of copper material used is minimized, achieving the optimal match between material cost and conductivity efficiency.

[0050] In one possible embodiment, the thickness of the aluminum plate in the non-lap area of ​​the copper-aluminum composite busbar is less than or equal to a preset aluminum plate cost constraint thickness, and satisfies: at an ambient temperature of T max The operating current is I max Under normal operating conditions, the maximum temperature of the copper-aluminum composite busbar is lower than or equal to the maximum allowable operating temperature of the copper-aluminum composite busbar for the electric drive; where T max Indicates the maximum operating ambient temperature of the copper-aluminum composite busbar, I max This indicates the rated current of the input motor. The preset aluminum plate cost constraint thickness refers to the maximum aluminum plate thickness allowed by the cost of aluminum plate materials. The aluminum plate thickness in the non-lap area of ​​the copper-aluminum composite busbar is limited to ensure that it does not exceed the preset aluminum plate cost constraint thickness. At the same time, temperature rise verification constraints are completed in conjunction with extreme working conditions, achieving a dual balance between structural material control and thermal safety performance under extreme working conditions.

[0051] In one possible embodiment, the thickness of the first copper plate and the thickness of the second copper plate in the bolt lap area of ​​the copper-aluminum composite busbar are less than or equal to a preset copper plate cost constraint thickness, and satisfy the following condition: at an ambient temperature of T... max The operating current is I max Under normal operating conditions, the temperature difference between the bolt lap area and the non-lap area of ​​the copper-aluminum composite busbar is less than a preset temperature difference threshold. The preset copper plate cost constraint thickness refers to the maximum copper plate thickness allowed by the cost of the copper plate material. By ensuring controllable material costs, the overall temperature rise of the copper-aluminum composite busbar is effectively balanced, reducing regional temperature gradient differences, improving overall thermal uniformity and thermal stability, and ensuring stable and reliable current transmission under full load and high-temperature harsh conditions.

[0052] In one possible embodiment, the thickness of the aluminum plate corresponding to the bolt lap area of ​​the copper-aluminum composite busbar is less than or equal to a preset aluminum plate cost constraint thickness, and satisfies: at an ambient temperature of T max The operating current is I max Under certain operating conditions, the temperature difference between the bolt lap joint area and the non-lap joint area of ​​the copper-aluminum composite busbar is less than the preset temperature difference threshold. While achieving economical material usage, this ensures uniform temperature rise across the entire range of the copper-aluminum composite busbar under extreme high temperatures and full-load current-carrying conditions. This effectively improves the fastening reliability, thermal stability, and long-term current-carrying stability of the lap joint structure, comprehensively enhancing the overall operational safety and service durability of the busbar in high-power transmission scenarios.

[0053] The copper-aluminum composite busbar is used to connect the AC output terminal of the SiC power module to the three-phase input terminal of the motor, adapting to a compact controller layout. As an example, the busbar is fixed with M8 bolts for end-face lap joints, with a bolt tightening torque of 8 N·m and a corresponding contact pressure F = 4500 N in the bolt lap joint area. After the copper-aluminum composite busbar is assembled, key operating parameters of this embodiment are obtained through inverter bench testing: the inverter switching frequency f is set to 15 kHz (i.e., f = 15 kHz) to match the power loss and electromagnetic interference balance requirements of mainstream automotive inverters, and the maximum operating ambient temperature T... max =85℃, and the maximum allowable operating temperature of the copper-aluminum composite busbar for the electric drive is set to 125℃, consistent with the maximum junction temperature of the device (i.e., the maximum allowable temperature rise of the copper-aluminum composite busbar for the electric drive is 40℃), and the rated current of the input motor (also the rated current under the most stringent operating conditions) I max =420A. At the same time, the bolt lap joint type (i.e. the contact point type of the bolt lap joint area) is determined to be copper-copper surface contact, clean surface, material and surface coefficient K=100, and contact form index m=1 for the bolt lap joint area.

[0054] like Figure 3 As shown in the embodiments of this application, the design method of the copper-aluminum composite busbar includes the following steps:

[0055] S1. Obtain the inverter switching frequency f and the maximum operating ambient temperature T of the copper-aluminum composite busbar under actual application conditions. max Input motor rated current I max .

[0056] S2. Calculate the skin depth of the first and second copper plates at the inverter switching frequency f. .

[0057] In one possible embodiment, the formula is used: The skin depths of the first copper plate 1 and the second copper plate 3 at the inverter switching frequency f were calculated. It achieves a theoretically precise match between copper plate thickness and the high-frequency skin effect, ensuring quantitative controllability of thickness design, effectively saving copper material usage and reducing costs. At the same time, it ensures that the copper-aluminum composite busbar has high current efficiency, uniform heating, and stable and reliable operation at the target switching frequency.

[0058] Among them, skin depth It represents the depth at which the field amplitude decays to 1 / e (approximately 37%) of the surface value, and is usually expressed in meters (m).

[0059] Inverter switching frequency f, unit: Hz; The magnetic permeability of copper is expressed in H / m. The electrical conductivity of copper is expressed in S / m (Siemens per meter).

[0060] As an example, , Represents the permeability of free space. H / m, This represents the relative permeability of copper. Copper is a non-magnetic material. ,therefore, H / m; Under operating conditions at 85℃, the conductivity of copper is γ = 5.4 × 10⁻⁶. 7 S / m. Therefore. Calculations show that δ ≈ 0.56 mm.

[0061] S3. Use the skin depth as the base thickness of the first copper plate and the base thickness of the second copper plate.

[0062] The skin depth is calculated based on the actual switching frequency f of the inverter, and the skin depth is directly used as the base thickness of the first and second copper plates. This allows the thickness of the first and second copper plates to accurately match the current skin effect distribution under high-frequency operating conditions, making full use of the high conductivity of copper plates. Under the premise of meeting the high-frequency current carrying requirements, the amount of copper material used is minimized, achieving the optimal match between material cost and conductivity efficiency.

[0063] As an example, the thickness of the first copper plate base is 0.56 mm, and the thickness of the second copper plate base is 0.56 mm.

[0064] S4. Set the ambient temperature to T. max Continuous loading current I max The thickness of the aluminum plate foundation was determined by finite element iterative simulation of the copper-aluminum composite busbar.

[0065] At the highest operating ambient temperature T max The rated current of the input motor (also the rated current under the most demanding operating conditions) I max Using finite element iterative simulation as boundary conditions, the thickness of the aluminum plate foundation is determined. This allows for the quantitative simulation of the busbar temperature rise, heat distribution, and current carrying characteristics under actual extreme working conditions. It accurately matches the conductivity, heat dissipation, and structural load-bearing requirements of the aluminum plate, ensuring that the temperature rise in the non-overlapping area is compliant, the current carrying capacity is stable, and there is no risk of overheating failure under extreme working conditions. This enables the scientific and quantitative design of the structural parameters of the non-overlapping area.

[0066] In one possible implementation, such as Figure 4 As shown, the method for determining the thickness of the aluminum plate base includes the following steps:

[0067] S41. Based on the initial thickness of the first copper plate, the initial thickness of the second copper plate, and the preset initial thickness of the aluminum plate, a first simulation model is constructed. The first simulation model is a finite element simulation model of a copper-aluminum composite busbar.

[0068] The thicknesses of the first and second copper plate foundations in the finite element simulation model of the copper-aluminum composite busbar were based on the skin depth. A joint simulation using ANSYS Icepak and Maxwell was employed to build the finite element simulation model, ensuring that the high-frequency current was entirely carried by the surface copper plate, preventing current penetration into the aluminum plate and thus avoiding increased high-frequency losses. As an example, the initial thickness of the aluminum plate was preset to 1.0 mm.

[0069] S42. Set the ambient temperature to T. max Continuous loading current I max Starting from the preset initial thickness of the aluminum plate, the thickness of the aluminum plate is gradually increased, and iterative simulation is performed until the highest temperature of the copper-aluminum composite busbar in the first simulation model is lower than or equal to the highest operating temperature of the copper-aluminum composite busbar allowed by the electric drive.

[0070] As an example, the ambient temperature was set to 85℃, and the rated current of the input motor, 420A, was continuously applied. The aluminum plate thickness started at 1.0mm and gradually increased in increments of 0.2mm. The highest temperature in the non-lap joint area of ​​the copper-aluminum composite busbar was monitored simultaneously to ensure that it did not exceed the maximum junction temperature limit of 125℃. The aluminum plate thickness was confirmed based on the simulation results.

[0071] S43. The aluminum plate thickness when the highest temperature of the copper-aluminum composite busbar in the first simulation model is lower than or equal to the highest operating temperature of the copper-aluminum composite busbar allowed by the electric drive is taken as the basic thickness of the aluminum plate.

[0072] As an example, let's assume the simulation results show that when the aluminum plate thickness is 1.8mm, the highest temperature of the copper-aluminum composite busbar is 123℃, which is below the limit of 125℃ and meets the temperature rise requirement; when the aluminum plate thickness is 1.6mm, the highest temperature of the copper-aluminum composite busbar reaches 126℃, exceeding the limit of 125℃, and cannot meet the requirements for long-term reliable operation. Therefore, the aluminum plate thickness is determined to be 1.8mm.

[0073] A finite element simulation model of the copper-aluminum composite busbar was built by combining the base thicknesses of the first and second copper plates with the initial thickness of the aluminum plate, using T... max and I max To simulate boundary conditions and accurately reproduce extreme working conditions, ensuring that the aluminum plate thickness meets the extreme usage requirements and avoiding overheating failure and material waste, an iterative simulation method of gradually increasing aluminum plate thickness was adopted to accurately determine the minimum aluminum plate thickness that meets the temperature requirements, thereby reducing manufacturing costs. The criterion of using the highest temperature of the copper-aluminum composite busbar meeting the electric drive allowable temperature was clarified, which is conducive to improving product quality consistency.

[0074] S5. The thickness of the first copper plate base, the thickness of the aluminum plate base, and the thickness of the second copper plate base are respectively used as the thickness of the first copper plate, the thickness of the aluminum plate, and the thickness of the second copper plate in the non-overlapping area of ​​the final copper-aluminum composite busbar.

[0075] As an example, the thickness of the first copper plate in the non-overlapping area of ​​the final copper-aluminum composite busbar is 0.56mm, the thickness of the aluminum plate is 1.8mm, and the thickness of the second copper plate is 0.56mm. That is, the cross-sectional parameters of the non-overlapping area of ​​the copper-aluminum composite busbar are locked as: 0.56mm for the first copper plate + 1.8mm for the aluminum plate + 0.56mm for the second copper plate. The total thickness of the copper-aluminum composite busbar is 2.92mm, which perfectly matches the installation space and takes into account both the goals of lightweighting and cost control.

[0076] S6. Calculate the contact resistance R in the bolt lap joint area. j .

[0077] As a critical node for current transmission, the bolt lap joint area exhibits significant contact resistance, generating additional Joule heat and forming localized hotspots that threaten the reliability of the copper-aluminum composite busbar and the system. Therefore, targeted structural optimization of the bolt lap joint area is necessary: ​​extending 10mm outwards from the center of the M8 bolt hole as the effective lap area, a structural adjustment is implemented within this area, thickening the copper plate and thinning the aluminum plate to reduce the maximum temperature of the bolt lap joint area. The bolt lap joint structure can be rectangular, triangular, trapezoidal, or other shapes that allow for localized thickening. In this embodiment, a rectangular localized thickening is selected. As an example, the thickened lap joint structure can be formed using a semi-molten rolling composite process. The copper-aluminum bonding surface undergoes sandblasting roughening treatment (Ra=2.0μm) to effectively remove the oxide layer and impurities, improving the bonding interface strength. The bonding strength is ≥160MPa, and process verification shows no risk of delamination or cracking, ensuring long-term structural stability.

[0078] In one possible embodiment, the formula is used: The contact resistance of the bolt lap joint area was calculated. The unit is usually μΩ (microohms); where F represents the preset contact pressure of the bolt lap joint area, in N; K represents the material and surface coefficient; and m represents the contact form index of the bolt lap joint area. K is obtained from a table based on the contact material, and m is obtained based on the contact point type of the bolt lap joint area. This method achieves the theoretical and precise calculation of contact resistance, improving the accuracy and reliability of the calculation results and providing a precise data foundation for subsequent simulation optimization of the bolt lap joint area.

[0079] In one possible embodiment, if the contact point type of the bolt lap joint is point contact (i.e., sphere to plane), then m = 0.5; if the contact point type of the bolt lap joint is line contact (i.e., cylinder to plane), then m = 0.7; and if the contact point type of the bolt lap joint is surface contact (such as copper busbar lap), then m = 1. By clearly defining the specific values ​​of m = 0.5, m = 0.7, and m = 1 corresponding to the three typical contact point types of bolt lap joints (point contact, line contact, and surface contact), the quantitative and standardized setting of the contact form index m is achieved, providing a reliable core parameter for the accurate calculation of contact resistance.

[0080] As an example, According to calculations, R j ≈ 0.218mΩ = 218μΩ.

[0081] S7. Import contact resistance and set the ambient temperature to T. max Continuous loading current I maxBy using finite element iterative simulation of copper-aluminum composite busbars with thickened copper plates and thinned aluminum plates in the bolt lap area, the thicknesses of the first copper plate, the second copper plate, and the corresponding aluminum plate in the bolt lap area of ​​the final copper-aluminum composite busbar were determined.

[0082] The contact resistance of the bolt lap joint area is pre-calculated and imported into the simulation model to accurately reproduce the actual electrical contact characteristics of the bolt lap joint area, improving the accuracy and engineering applicability of the bolt lap joint area structural design. A differentiated design with thicker copper plates and thinner aluminum plates is adopted for the bolt lap joint area. The low resistivity, high temperature resistance, and high contact stability of copper plates are used to compensate for the contact resistance loss in the bolt lap joint area, reducing Joule heat generation and optimizing the temperature rise distribution of the copper-aluminum composite busbar, thus improving the performance of the copper-aluminum composite busbar and significantly enhancing the system's reliability and efficiency.

[0083] In one possible implementation, such as Figure 5 As shown, the method for determining the thickness of the first copper plate, the thickness of the second copper plate, and the corresponding thickness of the aluminum plate in the bolt lap area of ​​the final copper-aluminum composite busbar includes the following steps:

[0084] S71. Select the bolt lap joint area and build a second simulation model based on the thickness of the first copper plate foundation, the thickness of the second copper plate foundation, and the thickness of the aluminum plate foundation. The second simulation model is a finite element simulation model of a copper-aluminum composite busbar with thickened copper plate and thinned aluminum plate in the bolt lap joint area.

[0085] As an example, the effective overlap area is defined by extending 10mm outward from the center of the M8 bolt hole.

[0086] S72, Contact resistance Import the second simulation model and set the ambient temperature to T. max Continuous loading current I max While keeping the total thickness of the copper-aluminum composite busbar constant, starting from the thickness of the first copper plate base, the thickness of the second copper plate base, and the thickness of the aluminum plate base, the thickness of the first copper plate and the thickness of the second copper plate in the bolt lap area are gradually increased, and the thickness of the aluminum plate corresponding to the bolt lap area is gradually decreased. Iterative simulation is performed until the temperature difference between the bolt lap area and the non-lap area in the second simulation model is less than the preset temperature difference threshold.

[0087] In one possible embodiment, the method of gradually increasing the thickness of the first copper plate and the second copper plate in the bolt lap area is as follows: according to a preset first gradient. The thickness of the first and second copper plates in the bolt lap area is gradually increased. The thickness of the aluminum plate corresponding to the bolt lap area is gradually decreased according to a preset second gradient. Gradually reduce the thickness of the aluminum plate corresponding to the bolt lap joint area. Among these, .

[0088] As an example, the ambient temperature was set to 85℃, and a continuous current of 420A was applied. While keeping the total thickness of the copper-aluminum composite busbar constant at 2.92mm, the thickness of the first copper plate and the second copper plate in the bolt lap area were gradually increased in increments of 0.1mm, starting from 0.56mm. Correspondingly, the thickness of the aluminum plate in the bolt lap area was gradually decreased in increments of -0.2mm. The temperature difference between the center of the bolt lap area and the non-lap area was monitored simultaneously. The preset temperature difference threshold was 3℃ to ensure that the temperature rise of the bolt lap area and the non-lap area tended to be consistent, thus eliminating local hot spots.

[0089] S73. When the temperature difference between the bolt lap area and the non-lap area is less than the preset temperature difference threshold, the thickness of the first copper plate, the thickness of the second copper plate, and the corresponding aluminum plate in the bolt lap area of ​​the second simulation model are used as the thickness of the first copper plate, the thickness of the second copper plate, and the corresponding aluminum plate in the bolt lap area of ​​the final copper-aluminum composite busbar.

[0090] As an example, suppose the simulation iteration results show that: when the thickness of the first copper plate and the second copper plate in the bolt lap area after local thickening are 0.86mm, the temperature difference is 4.8℃, which is higher than 3℃ and cannot meet the temperature rise uniformity requirement; when the thickness of the first copper plate and the second copper plate in the bolt lap area after local thickening are 0.96mm, the temperature difference is 3.2℃, which is close to but still higher than 3℃, and there is still a slight temperature rise difference; when the thickness of the first copper plate and the second copper plate in the bolt lap area after local thickening are 1.06mm, the temperature difference is 2.5℃, which meets the requirement of ≤3℃.

[0091] Therefore, the thickness of the first copper plate in the bolt lap area of ​​the final copper-aluminum composite busbar is 1.06 mm, the thickness of the second copper plate is 1.06 mm, and the thickness of the corresponding aluminum plate in the bolt lap area is 0.8 mm. Combined with the aforementioned thicknesses of the first copper plate (0.56 mm), the aluminum plate (1.8 mm), and the second copper plate (0.56 mm) in the non-lap area of ​​the final copper-aluminum composite busbar, the resulting structure is as follows: Figure 2 The copper-aluminum composite busbar structure shown.

[0092] Using a temperature difference between the bolt lap area and the non-lap area that is less than a preset temperature difference threshold as the iteration termination condition, the temperature rise in the bolt lap area and the temperature rise in the non-lap area tend to be consistent, realizing the overall temperature distribution of the copper-aluminum composite busbar. This effectively solves the problem of excessive heat generation and excessive temperature difference in the bolt lap area caused by contact resistance, while ensuring that the performance of the non-lap area is not affected. This ensures stable current carrying capacity and controllable heat generation throughout the copper-aluminum composite busbar, and improves the overall electrical reliability and service life of the copper-aluminum composite busbar.

[0093] After completing all the design and manufacturing of the copper-aluminum composite busbar, a temperature rise test was conducted on the copper-aluminum composite busbar: assuming it operates for 2 hours at a continuous current of 420A and an ambient temperature of 85℃, the temperature in the non-lapped area is 121℃, and the highest temperature in the bolt lapped area is 123.5℃, with a temperature difference of only 2.5℃. The temperature rise in the bolt lapped area is close to that in the non-lapped area.

Claims

1. A copper-aluminum composite busbar, comprising a first copper plate (1) in the upper layer, an aluminum plate (2) in the middle layer, and a second copper plate (3) in the lower layer, characterized in that: The thickness of the first copper plate and the thickness of the second copper plate in the bolt lap area of ​​the copper-aluminum composite busbar are greater than the thickness of the first copper plate and the thickness of the second copper plate in the non-lap area of ​​the copper-aluminum composite busbar, and the thickness of the aluminum plate corresponding to the bolt lap area of ​​the copper-aluminum composite busbar is less than the thickness of the aluminum plate in the non-lap area of ​​the copper-aluminum composite busbar.

2. The copper-aluminum composite busbar according to claim 1, characterized in that: The thickness of the first copper plate and the thickness of the second copper plate in the non-lap area of ​​the copper-aluminum composite busbar are equal to the skin depth of the first copper plate (1) and the second copper plate (3) under f. Where f represents the inverter switching frequency of the copper-aluminum composite busbar under actual application conditions.

3. The copper-aluminum composite busbar according to claim 2, characterized in that: The thickness of the aluminum plate in the non-lapped area of ​​the copper-aluminum composite busbar is less than or equal to the preset aluminum plate cost constraint thickness, and satisfies: at an ambient temperature of T max The operating current is I max Under normal operating conditions, the maximum temperature of the copper-aluminum composite busbar is lower than or equal to the maximum allowable operating temperature of the copper-aluminum composite busbar for the electric drive; where T max Indicates the maximum operating ambient temperature of the copper-aluminum composite busbar, I max This indicates the rated current of the input motor.

4. The copper-aluminum composite busbar according to claim 3, characterized in that: The thickness of the first copper plate and the thickness of the second copper plate in the bolt lap area of ​​the copper-aluminum composite busbar are less than or equal to the preset copper plate cost constraint thickness, and satisfy the following: at an ambient temperature of T max The operating current is I max Under the operating conditions, the temperature difference between the bolt lap area and the non-lap area of ​​the copper-aluminum composite busbar is less than the preset temperature difference threshold. The thickness of the aluminum plate corresponding to the bolt lap area of ​​the copper-aluminum composite busbar is less than or equal to the preset aluminum plate cost constraint thickness, and satisfies the following: at an ambient temperature of T max The operating current is I max Under certain operating conditions, the temperature difference between the bolt lap area and the non-lap area of ​​the copper-aluminum composite busbar is less than the preset temperature difference threshold.

5. A design method for a copper-aluminum composite busbar as described in any one of claims 1 to 4, characterized in that, include: Obtain the inverter switching frequency f and the maximum operating ambient temperature T of the copper-aluminum composite busbar under actual application conditions. max Input motor rated current I max ; Calculate the skin depth of the first copper plate (1) and the second copper plate (3) at the inverter switching frequency f. ; The skin depth As the base thickness of the first copper plate and the base thickness of the second copper plate; Set the ambient temperature to T. max Continuous loading current I max The thickness of the aluminum plate foundation was determined by finite element iterative simulation of copper-aluminum composite busbar; The thickness of the first copper plate base, the thickness of the aluminum plate base, and the thickness of the second copper plate base are respectively used as the thickness of the first copper plate, the thickness of the aluminum plate, and the thickness of the second copper plate in the non-overlapping area of ​​the final copper-aluminum composite busbar. Calculate the contact resistance of the bolt lap joint area ; Import the contact resistance Set the ambient temperature to T max Continuous loading current I max By using finite element iterative simulation of copper-aluminum composite busbars with thickened copper plates and thinned aluminum plates in the bolt lap area, the thicknesses of the first and second copper plates and the corresponding aluminum plates in the bolt lap area of ​​the final copper-aluminum composite busbar were determined.

6. The design method of the copper-aluminum composite busbar according to claim 5, characterized in that, The method for determining the thickness of the aluminum plate base is as follows: Based on the initial thickness of the first copper plate, the initial thickness of the second copper plate, and the preset initial thickness of the aluminum plate, a first simulation model is built; wherein, the first simulation model is a copper-aluminum composite busbar finite element simulation model; Set the ambient temperature to T. max Continuous loading current I max Starting from the preset initial thickness of the aluminum plate, the thickness of the aluminum plate is gradually increased, and iterative simulation is performed until the highest temperature of the copper-aluminum composite busbar in the first simulation model is lower than or equal to the highest operating temperature of the copper-aluminum composite busbar allowed by the electric drive. The thickness of the aluminum plate in the first simulation model at this time is taken as the basic thickness of the aluminum plate.

7. The design method of the copper-aluminum composite busbar according to claim 5, characterized in that, Calculate the skin depth of the first copper plate (1) and the second copper plate (3) at the inverter switching frequency f. The method is as follows: Using the formula: The skin depths of the first copper plate (1) and the second copper plate (3) at the inverter switching frequency f were calculated. ;in, Indicates the magnetic permeability of copper, This indicates the electrical conductivity of copper. Calculate the contact resistance of the bolt lap joint area The method is as follows: Using the formula: The contact resistance of the bolt lap joint area was calculated. Where F represents the preset contact pressure of the bolt lap joint area, K represents the material and surface coefficient, and m represents the contact form index of the bolt lap joint area. K is obtained from a table based on the contact material, and m is obtained based on the contact point type of the bolt lap joint area.

8. The design method of the copper-aluminum composite busbar according to claim 5, characterized in that, The method for determining the thickness of the first copper plate, the thickness of the second copper plate, and the corresponding thickness of the aluminum plate in the bolt lap area of ​​the final copper-aluminum composite busbar is as follows: Select the bolt lap joint area, and build a second simulation model based on the thickness of the first copper plate base, the thickness of the second copper plate base, and the thickness of the aluminum plate base; wherein, the second simulation model is a finite element simulation model of a copper-aluminum composite busbar with thickened copper plate and thinned aluminum plate in the bolt lap joint area; The contact resistance Import the second simulation model and set the ambient temperature to T. max Continuous loading current I max While keeping the total thickness of the copper-aluminum composite busbar constant, starting from the thickness of the first copper plate base, the thickness of the second copper plate base, and the thickness of the aluminum plate base, the thickness of the first copper plate and the thickness of the second copper plate in the bolt lap area are gradually increased, and the thickness of the aluminum plate corresponding to the bolt lap area is gradually decreased. Iterative simulation is performed until the temperature difference between the bolt lap area and the non-lap area in the second simulation model is less than the preset temperature difference threshold. The thicknesses of the first copper plate, the second copper plate, and the corresponding aluminum plate in the bolt lap area of ​​the second simulation model at this time are taken as the thicknesses of the first copper plate, the second copper plate, and the corresponding aluminum plate in the bolt lap area of ​​the final copper-aluminum composite busbar.

9. A motor control system, characterized in that: Including the copper-aluminum composite busbar as described in any one of claims 1 to 4.

10. A vehicle, characterized in that: Includes the motor control system as described in claim 9.

Images