E-Mobility Engineering 019 | In conversation: Stephen Lambert l WAE EVR l Battery case materials focus l Quality control insight l Clipper Automotive Clipper Cab digest l Optimising battery chemistries insight l Powertrain testing focus

May/June 2023 | E-Mobility Engineering 19 it recreated the speed and quality of controllability we’ve previously achieved in motorsport – and does so within automotive requirements – then it would be worth it.” Themechanical design of the inverter also had to be rethought to enable quick and straightforwardmanufacturing, as opposed to the intricate designs, low- volume numbers and long lead times of motorsport inverters. In its current form, the IPG5weighs 5.5 kg andmeasures 262.5 x 176 x 82mm. It has a peak gravimetric power density of just over 90 kVA/kg (or just over 130 kVA/litre if considering volumetric power density) and complies with ISO 26262, ASIL-D. It supplies power up to a peak of 900 V or current up to 540 Arms, assuming a liquid-coolant flow rate of 10 litres/minute, an 8 kHz switching frequency (although its peak variable switching frequency is 32 kHz) and an operating power efficiency of 97%, up to 99% at peak. Most of that efficiency comes from the use of SiC technology, which Lambert notes has been used by McLaren Applied for developing inverters for Formula One and Formula E since 2012. He and his team therefore spent further time looking into factors such as cost optimisation, transistor quality and supply chain reliability, eventually choosing STMicroelectronics as its SiC supplier. “When it comes to designing and optimising SiC topologies, some companies will just swap out their silicon MOSFETs for SiC MOSFETs and think it’ll be fine,” Lambert says. “That will work, and the inverter will be slightly more efficient, but the inverter is not making the best of the new transistors, whether that be in terms of motor speed, switching frequency or how the motor is optimised. “Some people forget that when you use SiC, you unlock higher speeds for your motor. And if you have a faster motor, you can make it smaller for the same amount of power. Also, if you want to produce higher volumes of vehicles, taking out motor mass could be a lifesaver because of the rawmaterials costs you’re saving, on top of the weight you’re taking out.” Beyond that, the controllability necessary for using SiC can as mentioned offer new software-defined capabilities, be it for greater efficiency, driveability and so on. “Matlab Simulink’s auto code generation has been key to the success of McLaren Applied’s systems in Formula One for years now,” Lambert says. “In many ways it’s our bread and butter, and we’ve now taken it into automotive with some control products that could be directly embedded with code from Simulink before production. “At the time, nobody elsewas doing that, and that capability is closely linked to our simulationwork. If you can simulate something and then copy &paste the Simulinkmodel into your code, itmassively reduces your development time.” Future plans Lambert and his colleagues view EVs as one part of a burgeoning low-carbon world. It will be filled with consumers actively interested in their own energy usage, and who expect greater connectivity with and access to data between their vehicles and their homes through software-defined portals. “As powertrains become more efficient, EVs will start to be seen as these big energy stores sitting next to houses,” he says. “And as well as that opening up V2X opportunities, everything – the EV, the chargers in your house, your heat pump and local renewable energy turbines – will need power electronics.” He comments that GaN will be useful for LV automotive applications such as DC-DC converters and OBCs, noting that GaN laptop chargers are finding commercial success given their small size and minimal cooling needs. That will push GaN towards widespread use in the low-carbon world, he says, although he anticipates SiC continuing to dominate higher-current systems working above the 650 V limit that GaN tends to be capped to. “EV powertrains won’t sit still either. Even as they become more software-defined, there will definitely be a big shift towards fully integrated drive units, with motors, inverters and transmissions all consolidated together,” he says. “High-performance EVs in particular will push the development of more torque-vectoring EDUs, with control of individual motors to individual wheels. That’ll be something especially exciting to look out for.” McLaren Applied’s first e-mobility product is the IPG5 inverter, which runs on SiC transistors and supplies power up to a peak efficiency of 99%