Busbars for e-mobility: State-of-the-Art Review and a New Joining by Forming Technology

Abstract

The changes in the automotive market and their effects on industry are nowadays hot topics in metal forming seminars and conferences around the world. The rise in the number of electric vehicles will inevitably lead to a decrease in the demand of components for combustion engines and power drive trains. Typical forming components such as pistons, connecting rods, valves, camshafts, crankshafts, multispeed gear boxes and others that exist in diesel or petrol vehicles, will no longer be required.However, the lightweight construction requirements for the body-in-white of electric vehicles, the production of components for asynchronous motors and the fabrication of battery components, namely busbars, are bringing new challenges and opportunities for the metal forming industry. This chapter is focused on busbars, which are metallic strips or sheets that are utilized to distribute electric power to multiple equipment such as the electric motor, the electric power steering unit, and the AC/DC converters. In particular, the chapter addresses the challenge of replacing copper busbars by hybrid busbars made from copper and aluminium, due to the expected savings in weight and cost.For this purpose, the authors discuss the challenge of connecting copper to aluminium in hybrid busbars by means of existing joining technologies and introduce a new joining by forming process aimed at connecting hybrid busbars at room temperature without giving rise to material protrusions above and below the sheet surfaces. The effectiveness of the new process is compared against fastening by measuring the electric resistivities in both types of hybrid busbar joints. Finite element analysis gives support to the presentation and proves to be suitable for the electrothermo-mechanical analysis of busbar connections.

Double-sided injection lap riveting

“…The goal is to give aluminum an importance similar to copper as a key material in energy transition and reduction of greenhouse gas emissions. Despite the lower electrical conductance of aluminum, requiring busbars to be 2.3 times thicker than those made from copper to ensure the same electric current capacity, the tendency is clearly favorable to aluminum busbars because they provide 32% mass reduction and approximately 80% cost savings for the same electrical conductance [15]. Under these circumstances, the investigation was performed in unit cells with 100 mm length and 50 mm width made from 2 and 5 mm thickness aluminum AA6082-T6 sheets that were designed to replicate the fabrication process and the thermo-electrical performance of the busbar joints in service.…”

Thermo-electrical performance of hybrid busbars: An experimental and numerical investigation

“…The thicknesses of the aluminum and copper strips were equal to 2 and 5 mm, respectively, for obtaining a cross-section area ratio A Al / A Cu = 2.5 close to the ideal value of 2.3 that ensures equal current flow in both conductors. 12…”

“…The thicknesses of the aluminum and copper strips were equal to 2 and 5 mm, respectively, for obtaining a cross-section area ratio A Al / A Cu = 2.5 close to the ideal value of 2.3 that ensures equal current flow in both conductors. 12 The mechanical characterization of the strip materials at ambient temperature was performed by means of tensile tests in an Instron 4507 universal testing machine. The specimens were extracted from the strips in accordance with the ASTM standards E8/E8 M 13 and the results of the tests are summarized in Table 1.…”

Injection Lap Riveting of Aluminum Busbars—A Thermo-Electro-Mechanical Investigation

“…In practical terms, this means that aluminum busbars require greater cross-sections than copper busbars to ensure the same electric current-carrying capacity. However, this is not a problem for automakers because, as was recently shown by Sampaio et al [2], aluminum busbars provide 32% mass reduction and 84% cost savings, when compared to copper busbars with similar electric conductance.…”