E-Mobility Engineering | September/October 2023 71 Busbars and interconnects | Focus and the surrounding components,” he says. “We have also developed the means to test and analyse thermal maps of different conductors in the lab, where we can help manufacturers accelerate understanding of different configurations for the thermal management of such conductors.” Dimensional stability is critical to ensuring that systems perform as designed, the electrical, industrial and power management company’s expert says, citing the use of graphene in busbars to enhance such stability. This variant of carbon, made up of single layers of carbon atoms joined in a network of hexagons, can be processed into busbars of extreme flatness, which helps transfer heat out of the system via passive cooling mechanisms, he explains. Many new applications need high currents because of demanding e-mobility drive profiles and fastcharging requirements. Reducing ohmic losses and managing their heat dissipation effect in confined areas are becoming increasingly important aspects of many designs. “Thermal simulation tools are increasingly used in the very early stages of a thermal management project to take into consideration the whole system architecture and optimise heat dissipation and conductor designs,” the power transfer, management and materials expert notes. While the cell form factor used in a battery does not affect busbar and interconnect designs in any fundamental way, battery architectures and cell connection systems have had to adapt to cylindrical, prismatic and pouch cells, and the placement of terminals is important, he points out. “Positive and negative terminals are usually at opposite ends of a cylindrical cell, but newer configurations that put both polarities on the same end are gaining popularity in the market,” he says. Each form factor has a particular connection solution that the industry has more or less converged on, the precision metal stamping and ultrasonic welding provider’s expert notes, although packs based on cylindrical cells still exhibit significant variation in current collector geometries and design. Design tools Design tools such as FEA, mould flow analysis, CAD, CAE and computer aided optimisation (CAO) are as important in the area of conductor design as in any other aspect of engineering an EV powertrain. A design will usually start with CAO completed with several simulation tools to adapt and optimise the component at the system level, the power transfer, management and materials expert points out. Supporting this will be the interpretation of results from thermal and vibration simulations, which helps to accelerate design cycles. The CNC bending specialist says its customers can design their busbars in any CAD program they like, so long as they use the design guidelines the company provides to ensure the bars can be successfully bent into the required shape. When the CAD file comes from the customer, it is imported into and analysed by the company’s inhouse programming system that checks for feasibility, looking at minimum lengths and bend radii, for example, as part of a full CAD/CAM integration. “We have an integrated simulation tool, so we can run a simulation of the part to check for collisions [with other areas of the part or the tooling] and run rates,” one of the company’s experts says. Knowing the run rates is important for calculating manufacturing times. “This is available on the bending machine as well as in an office setting, so that the customer’s engineers can check parts and run simulations,” he adds. “This all happens before bending. Then, after the first busbar is bent, it goes into a measuring cell that checks it in three dimensions so that inspection software can compare the results from the 3D measurement cell with the original 3D model that was fed into the machine. “The software then generates correction data for the second production run, so within two or three cycles you get a part that matches your 3D master. Then, data from whatever you have done on the bending machine and then measured can be exported and fed back into the customer’s CAD system.” Another of the company’s Stamping can produce a wide variety of shapes, and stamped parts can be bent after stamping if necessary, but changes to shapes require new tooling (Courtesy of Wiegel)
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