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

Peter Donaldson reports on how lamination technology has evolved in recent times to meet changing demands from the EV industry Layer by layer W hether or not governments eventually ban the manufacture of fossil fuel-powered vehicles, it is clear that the electrification of transport fleets is set to accelerate and that the EV industry will therefore need traction motors in massive numbers with consistent quality at low cost. This pressure affects every component of these electrical machines, not least the laminations that form the rotor and stator cores. Along with low-resistance copper windings and powerful permanent magnets, rotor and stator cores shape the performance and efficiency of rotating electrical machines, and they must be built from thin layers of highly conductive material, principally steel alloys. Such laminations are the means of minimising loss-generating, heat- emitting eddy currents generated in them by electromagnetic interaction with the currents passing through the windings. One electrical steel producer we consulted in connection with this article notes that the market for traction motors and consequently for motor laminations is one of the fastest growing parts of the automotive industry. They describe the sector as being very dynamic, with fast-changing requirements for motor characteristics driving continuous development of technologies and materials. Also, a lamination tooling specialist describes the growth in the sector as exponential. It adds that many corporations in the automotive industry that for decades have supplied parts for IC-engined vehicles have seen the writing on the wall and are trying to make inroads into the EV sector, many of them by developing their own drive units. With so many new players in the market, the specialist says, lamination designs have evolved significantly over the past decade. A new generation of motor designers have extended the envelope for lamination geometries, and many old rule-of-thumb constraints have been pushed to the limit. Minimising losses Eddy currents are closed loops of electric current induced in conductors by changes in magnetic fields, circulating in planes perpendicular to the magnetic fields. According to Lenz’s law, eddy currents create their own magnetic fields that oppose changes in the initial magnetic fields that created them. That reduces the efficiency of electrical machines. Not only is the machine effectively fighting itself, the currents also generate heat, which represents lost energy as it has to be removed to keep the motor at a safe operating temperature. Very thin laminations in the cores of electrical machines are essential to eɉciency as tOey liTit tOe siae anK strenNtO of inKuceK eKKy currents tOat sap po^er anK Nenerate ^aste Oeat (Courtesy of 7orscOe) 64 Winter 2021 | E-Mobility Engineering