18 rapid r&d and innovating crucial new forms of pole combinations, resonance workarounds, and cooling to reach the customer’s torque, power and packaging constraints. For instance, when getting heat out of the stator proved impossible for the three-layer winding that YASA had initially opted for (specifically due to how hard Jaguar pushed them in testing), Woolmer and his team switched to an edge winding in which cooling fluid runs in contact with a single winding layer. A subsequent series of tip tests (consisting of about 10 rapid, 0-60 mph acceleration and braking cycles) by Jaguar found the new cooling design could withstand around 17 cycles without derating. This has led to a cooling approach unique to YASA’s modern motors in which cooling oil flows directly past the copper, bypassing the many layers of epoxy, slot linings and jackets typically seen in radial machines, and taking advantage of the thinner componentry of the axial-flux topology. “Jaguar were happy, henceforth putting our motors into five or six C-X75s to take to the press, with those cars performing fantastically, and then the project got cancelled,” Woolmer says. “It was meant to go into a limited, 250-unit production run and, for us, 500 motors would have been a big deal, but we’d still learned how to massively step up our capabilities and that of our technology, and it led a year or two later to our Koenigsegg project.” By that time, Woolmer and his team had distilled these new capabilities into the higher-speed YASA 400, and Koenigsegg sought to install two YASA 750s on the rear axle of its Regera PHEV touring sportscar, with a YASA 400 on its engine. As both motors were now largely COTS products, this collaboration saw only minor modifications and custom work compared with the Jaguar and other projects. With around 200 Regeras meriting 600 YASA motors, this provided a vital runway for YASA to go on to work on numerous series-hybrid powertrains with McLaren, Ferrari, Lamborghini, and more. “That took a new generation of technology and re-engineering, going from lab-built parts to something that could go down a production line – from bonding techniques to laser-welding, from machined glass fibres to moulded polymers, and so forth,” Woolmer says. Machines making machines This new generation is enshrined in YASA’s facility at the Oxford Pioneer Park in Yarnton, Oxfordshire, which is the first model factory for producing its e-motors at scale. “To get to where we are with this facility, it has taken a lot of inventing machines that could make our machines. People take for granted that there’s a pre-existing supply chain for everything we want to do, and there just wasn’t,” Woolmer says. “Probably 70% of the machines in the factory have been designed by YASA’s automation team; the other 30% includes some COTS machines they’ve modified too. For example, we can use a balancing machine to balance the rotors – that’s a COTS machine and process – but the single-layer, edge-winding process for our stator coils was developed in-house, as was the way we impregnate them. We absolutely could not have afforded to go to a big automation consulting company to get a process developed for us, so making one in-house was the way to go.” Further examples exist. For instance, approaches for laser-welding polymer components are widespread in automotive, but extremely rare in electric motor manufacturing, so YASA’s technique was also developed in-house. July/August 2024 | E-Mobility Engineering In conversation | Tim Woolmer Early collaborations for YASA included designing and providing e-motors for Jaguar’s hybrid C-X75 concept car... (Image courtesy of Jaguar) ..and for the Koenigsegg Regera (Image courtesy of Koenigsegg)
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