6 The Grid Modular powertrain ZF has developed a modular drive system for EVs that boosts efficiency and reduces size, writes Nick Flaherty. The SELECT platform covers electric motors and transmission to the inverter and AI-enhanced control software. “If you just optimise one piece you miss out on the global optimisation and you have lower efficiency,” says Dr Otmar Scharrer, senior vice president r&d, electrified powertrain technology at ZF. “SELECT is the result of that optimisation. It’s a platform with four parts. The reducer is the transmission, which you definitely need in an EV as the motor runs faster than the wheels, and that needs a ratio of between 1:10 and 1:12. Then, we have the electric machine, the motor and the inverter and the software that is the brains of the system.” em:SELECT for electric motors, which covers both proven Permanently Excited Synchronous Machines and Asynchronous Machines through to new concept Separately Excited Synchronous Machines, does not need magnets that use rare earth elements (REEs). This avoids supply chain issues with REEs from China. This has 93% efficiency with peak power from 150 to 300 kW and torque from 3500 to 5500 Nm. The volume of 66 L is a reduction of 19%, while the weight of 89 kg is a 15% reduction compared with the latest systems. The 300 kW in:SELECT inverter supports both 800 and 400 V systems. “The idea of the in:SELECT was to develop a very scalable and modular platform, with variations that are suitable for the e-motor packaging, but that is just one variant,” says Matthias Zechmann product manager for the inverter platform. “The platform has both SiC and IGBT – where efficiency is not the highest requirement then it is IGBT – all in the same space in the DDP or DQP packages used by ST for Tesla, which allows us to have a flexible module. “The design of the liquid cooling system has been optimised with an AI method for the different variants; perhaps an aluminium cooler for 400 V IGBT, but on the other side with the thermal behaviour for an 800 V premium vehicle, we may need a copper cooler with a baseplate with an optimised fin structure, but all within the same module and baseplate configuration.” The standard two-level inverter is 4–5 cm thick with a DC link capacitor and an EMC filter. The control and gate driver board are produced on a sub-assembly production line. “We would separate out the control and driver board in the future but at the moment we do not see that as necessary,” says Zechmann. “All the variants are flexible for concepts for commercial vehicles as well as off-road and construction,” he says. The sw:SELECT software uses two cores: one with the application software and the second for drivers with dedicated customer interfaces. “We do not change the base core but change the parameters and use the predefined interface to communicate to the customer system,” he says. “There is a lot of AI in the software,” he says. “One of the key factors is the temperature as this derates the drivetrain. You need to identify the hottest spots in the drivetrain. So, we have an AI system that estimates the maximum temperature on the hottest spots. This allows us to go much closer to the limits of the drivetrain,” he adds. POWERTRAINS September/October 2025 | E-Mobility Engineering A modular integrated drive system (Image courtesy of ZF)
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