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C h a p t e r 6 | Po w e r S e m i c o n d u c t o r s a n d O f f b o a r d C h a r g i n g f o r C o m m e r c i a l Ve h i c l e s access to power tools and accessories like chargers, saws, compressors, etc. Semiconductors used for such power converters will likely be a mixture of Si-MOSFETs, insulated-gate bipolar transistors (IGBTs), and, in some cases, SiC MOSFETs. Finally, electric powertrains responsible for transferring energy into motors can easily experience voltages exceeding 800V at hundreds of amps. Thus, IGBTs or SiC MOSFETs are the most frequently used devices. While IGBTs have a proven track record in such applications and are therefore the device of choice in commercial vehicles, SiC MOSFETs are opening a path to achieve higher efficiencies. What role would power semiconductors play in EV energy storage for electrical grids? The introduction of EVs presents electric grids with a new possibility: decentralized energy storage. With the growing quantity of EVs, a huge number of batteries gets connected to the mains at any one time; this setup could be leveraged to both store excess energy and provide energy to the grid during peak demand. Take the fleet of 480,000 US school-buses as an example. Those are idle at mid-day and during summer vacation. Assume a single bus can contribute 100 kWh of storage capacity, this single fleet can add 48 GWh. Considering each bus supplies 50 kW, this highly decentralized, virtual power bank provides up to 24 GW. That is equivalent to the power of 10 nuclear plants and the storage capacity, far larger than most pumped-hydro power-plants offer. Second, power semiconductors play a key role in charging commercial vehicles at megawatts of power along highways. At these power levels, efficiency becomes even more important. In contrast to the modular approach seen for passenger cars, a monolithic system based on just 12 high- power thyristors, powered from a medium-voltage transformer offers a way to 99.7% efficiency, in a most compact and reliable setup. If using vehicles for grid energy storage, power semiconductors are the major key component in these systems. As energy goes through the semiconductor twice, into the battery and back to the grid, losses double, so efficiency is on top of the list." Martin Schulz Global Principal, Application Engineering, Littelfuse 30 7 Experts on Automotive Powertrains