1. Current carrying capacity of the busbar
When current flows through the busbar, a current density distribution is generated on the conductor. Figure 1 shows the current density values and vector distribution of a simulated busbar electrode.
As can be clearly seen from Figure 1, the current flows from the beginning to the end of the conductor, and the current density vector is distributed inside the conductor like water. When the current density vector encounters an "obstacle," it skillfully bypasses it and continues its journey.
2. Heat generation of the motherboard
Resistivity is a physical quantity used to represent the resistance characteristics of a material. It is a fundamental property of a conductor and is represented by the symbol ρ. When current flows through a laminated busbar conductor, it generates a certain amount of heat. The heat generated per unit volume of the conductor (i.e., the heat generation power density) can be calculated using equation (1):
As shown in equation (1), under the same current density distribution, the higher the resistivity of the conductor, the greater its heat generation. Therefore, in the design of multilayer busbars where temperature rise is a key limiting factor, conductor materials with low resistivity should be selected first. The heat generation power density and steady-state temperature rise of the busbar conductor can also be simulated and calculated using software. Figure 2 shows the simulated heat generation power density distribution of the above-mentioned busbar conductor, and Figure 3 shows the simulated steady-state temperature distribution of this busbar conductor under 30℃ environmental and natural convection conditions.
Furthermore, according to formula (1), it can also be concluded that, under the condition of constant resistivity, the greater the current density of the conductor, the greater the heat generation. The following will conduct a simulation study on the influence of the current density of the conductor on the steady-state temperature rise. Figure 4 shows the simulation model and boundary conditions of a copper conductor with a narrow channel in the middle.
Figure 5 shows the heat generation power density and steady-state temperature distribution of the copper conductor when the input current i is 100A. It can be seen that the heat generation power density and temperature are highest in the narrow section in the middle of the copper conductor. The congested channel leads to a high-density current distribution, much like traffic congestion. Therefore, reducing the temperature rise of the busbar conductor is equivalent to rationally designing the current density of the conductor.
Figure 6 shows the simulated maximum temperature of the copper conductor as a function of the input current i. The simulation verifies the conclusion that "when the resistivity remains constant, the greater the current density of the conductor, the greater the heat generation."
3. Optimization of the busbar
The laminated busbars produced by Shanghai Yingfeng Electronics consist of flat conductors coated with an insulating film of adhesive. To reduce the resistance of the circuit and enhance the thermal dissipation capability of the conductors, metals with high electrical conductivity and good thermal conductivity should be selected as conductor materials. The conductors of the laminated busbars are mainly copper, meaning that the conductors account for the highest material cost. Therefore, in the optimization design of the busbar, the minimum number of conductors should be used to meet the current-carrying capacity requirements of the busbar. Figure 7 proposes an optimization method for the laminated busbar electrode plate, and Figures 8, 9, and 10 show the simulated current density vector distribution, heat generation power density distribution, and steady-state temperature distribution of the busbar electrode plate before and after optimization, respectively.
The simulation data above shows that by optimizing the design of the laminated busbar plates—specifically, eliminating the large, unused "ghost town" in the upper left corner—the current-carrying capacity of the busbar was not significantly weakened while saving copper material. Therefore, this optimization design method provides valuable guidance for engineers in future laminated busbar design processes.
4. Conclusion
By performing electrothermal coupling simulation on the busbar, the flow of current (electrons) in the busbar conductors can be clearly observed, and even the heat generation power density and steady-state temperature distribution of the conductors can be obtained. Following the direction of electron flow, Shanghai Yingfeng Electronics proposed an optimized design method for the laminated busbar electrode plates. This method has been verified by simulation and is of great significance for guiding engineers in designing laminated busbars and achieving energy conservation and cost reduction for the company.
