ISSUE 012 Winter 2021 Sigma Powertrain EMAX transmission dossier l In conversation: David Hudson l 48 V systems focus l 2021 Battery Show North America and Cenex-LCV reports l Everrati Porsche 911 digest l Switching insight l Motor laminations focus

Focus | Motor laminations Acknowledgements The author would like to thank Patrick Walker, Jaydip Das and Mingda Liu at Carpenter Electri ication, Barry Lee at LH Carbide, Markus Roever at Schuler Group, Basjan Berkhout at Tata Steel Europe, and Roman Sonnleitner at Voestalpine Steel Division for their help with researching this article. stack manufacturer. Their chemical composition would be acceptable, but grain size and texture would differ from those of good standard material. Soft magnetic composites consisting of ferromagnetic powders, the particles of which are surrounded by an insulating film, can be built up into complex 3D shapes in AM machines, and they have found uses in electromagnetic systems. However, the permeability and strength of the cores in which they are used is relatively poor and have so far limited the applicability of these materials. While they have the potential to reduce losses and improve power density, the technology has some way to go before it is mature enough to demonstrate parts with the right mechanical and magnetic properties, along with the scalability for volume production. As an aside, the use of AM could lead to improvements in the design of the dies used to stamp out the laminations, because stamping is so much quicker and more efficient. Future directions The trend towards thinner laminations with lower losses and greater strength is expected to continue, says the electrical steel maker, adding that bonding technologies will evolve. If they prove low enough in cost and fast enough in manufacture, they could replace interlocking and perhaps even welding as a means of holding laminated stacks together. The use of backlack in particular is expected to grow. Lamination thicknesses down to 0.25 mm are expected to be routinely used in large commercial production runs, according to the stack manufacturer, while stress- relief annealing is likely to see more widespread use to remove the influence of the stamping process on magnetic properties. Motor designers are expected to continue introducing more complex features into lamination stacks in the effort to optimise cooling as well as magnetic performance and overall efficiency, the speciality alloys provider says, who also anticipates that further progress in automation and process optimisation will lead to consistent and tighter geometric tolerances. Further, with enhanced testing finding disparities between magnetic samples and the final stack, it provides an opportunity to target the specific problems revealed. Traction motors are expected to benefit from improvements in the way backlack is used, with a focus on greater automation to deal with the problems arising from the need to handle loose laminations, for example, better suiting it to mass production. The metal forming specialist has developed a fully automated system that collects freshly stamped steel layers from underneath the progressive die set and transfers them to free-standing bonding units. These units are designed to allow full control of process parameters such as pressure, temperature and time, and are offered as a turnkey end-to- end system encompassing all the processes, from de-coiling of the raw material to completing the stack. The company proposes a system combining a high-speed press and bonding stations capable of turning out more than 500,000 bonded rotor stack a year, with the flexibility to adapt to different part sizes, volumes and ramp-up rates, and with digital solutions for traceability, data archives and process improvements. This kind of approach is likely to be essential to generate the production volumes required to electrify global transport in the timescales currently envisaged. A production station for a cold-stamping process for lamination stacks, which combines prime electrical steel with a full-face bonding process (Courtesy of Voestalpine Automotive Components Nagold) 72 Winter 2021 | E-Mobility Engineering