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

Acknowledgements The author would like to thank Amir Ranjbar at Dana, Ben Karrer at Eaton, Martina Giu rida at STMicroelectronics, Dr Jurgen Braunstein at CSM, and Alexander Nebel and Maawad Makdessi at Yageo for their help with researching this article. switching PWM topologies. They also represent a single point of failure for many critical powertrain systems. Using a decentralised power delivery with modular power components enables smaller, less powerful 48-12 V converters to be distributed throughout the vehicle close to the 12 V loads for higher efficiency and lower losses. For a given power level, the current is four times lower at 48 V than in a 12 V system and has 16 times lower losses. At a quarter of the current, the cables and connectors can be smaller, lighter and cheaper. The decentralised power architecture also has significant thermal management and power system redundancy benefits. The 48 V output from the battery is distributed to the various high-power loads in the vehicle, maximising the benefits of lower current and lower losses, and resulting in a physically smaller and lighter power network. Depending on a load power analysis of the various distributed loads, one module can be designed and qualified for the right power granularity and scale to be used in parallel arrays. By using distributed modules instead of a large centralised DC-DC converter, N+1 redundancy is also possible at a much lower cost. This approach also has advantages if the load power changes during the vehicle’s development phase. Instead of implementing changes to a full ground- up custom power supply, engineers can either add or eliminate modules. Another design advantage is reduced development time, as the module is already approved and qualified. A 48 V power distribution network still has significant benefits, but now the power system designer has the additional challenge of a high-power 800-48 V or 400-48 V conversion, which requires isolation but not regulation. Better voltage regulation is one benefit of decentralising the placement of 48-12 V converters. By using regulated PoL converters, the high-power upstream converter can use a fixed-ratio topology. This is extremely beneficial owing to the wide input-to-output voltage range of 16:1 or 8:1 for 800-48 V and 400-48 V respectively, but using a regulated converter over this range is very inefficient and presents a large thermal management problem. It would be difficult and costly to decentralise this high-voltage isolated converter owing to safety requirements in distributing the 400 or 800 V. However, a high-power centralised fixed-ratio converter can be designed using power modules instead of a large DC-DC converter. Power modules of a suitable power level can be developed and then easily paralleled for a range of vehicles with differing powertrain and chassis electrification requirements, with efficiencies of 98% and power densities of 2.6 kW/cu in, significantly reducing the size of the centralised high-voltage converter. Conclusion Naturally there is an immediate focus on 48 V power distribution for mild hybrids, even though the P0 topology has a limited design life as hybrids are being phased out from 2030 in many markets. The benefits of improvements in higher currents in 48 V subsystems, from compressors to pumps and heaters, is supporting higher power and efficiency across vehicle designs. This is also leading to the development of passive 48 V components, from capacitors to choke filters, that are optimised for higher power applications. However, the emergence of 48 V mild-hybrid systems is also leading to the development of 48 V power distribution networks in battery- electric vehicles with much thinner and lighter wiring harnesses to cut vehicle weight. This is driving the development of unregulated 400/800- 48 V DC-DC converters to power 48 V peripherals directly. It is also leading to local regulated PoL 48 V DC-DC converters to power electronics with a more efficient power distribution. Focus | 48 V systems A distributed 48 V power distribution network (Courtesy of Vicor) 40 Winter 2021 | E-Mobility Engineering