Silicon carbide (SiC) devices for the next-generation of electric vehicles
Sales of battery-electric vehicles (BEVs) are increasing as consumers and automakers alike benefit from European government subsidies for electric vehicles. Momentum is gathering pace as automakers including Ford, Jaguar Land Rover and Volvo have all announced plans to phase out internal combustion engines in their vehicles. Despite the small steps being taken so far by the technology, the move towards an electrified fleet in Europe is unstoppable and the days of petrol and diesel engines are already numbered. It is a question of when, not if, we will all be driving electric cars in the future. But before we reach this point, the technology behind BEVs needs to evolve to overcome a number of challenges, which include the size and efficiency of their drivetrains, the speed at which they can be charged and the range that they can cover. A crucial element in all this is the inverter. This component controls the input of electricity from the battery or batteries to the motor. Aside from converting incoming direct current to alternating current, the inverter controls the variability of power supplied to the motor when the driver demands it. As motors develop and migrate from 400-volt electrical systems to the far more versatile 800-volt units, the inverter is playing a crucial role. Increasingly, the industry is moving away from silicon to the use of silicon carbide inverters (SiCs), which have a number of significant advantages when twinned with high-voltage systems. Thomas Steffen, Senior Lecturer in Control Engineering at Loughborough University in the UK, explains: “A conventional inverter is about 97% to 98% efficient in moving energy from the battery to the motor, and a SiC-based inverter can push this to an amazing 99%. Although this is only a modest increase of 1% to 2%, the benefits for the whole vehicle can be more significant.” The two materials are very different in that they have varied physical parameters. Silicon carbide has the advantage that it is well suited to higher thermal conductivity, which is important in high-revving, high-voltage motors. “Compared with other silicon conductors, silicon carbide has a higher maximum operation temperature, which means you can squeeze more power out of it,” says Roland Bittner, a senior engineer at Semikron Elektronik, which is a partner of Drivemode, an EU research project. Its goal is to produce small adaptable electric modules consisting of power electronics including an SiC-inverter, a gearbox, and the motor itself. These modules are capable of being scaled up from one unit to four according to the power requirements of different vehicle segments. SiC inverters are ideal in such a modular approach because they allow a reduction in the size of all the crucial components. Bittner says: “If you go to higher battery voltage [such as 800V] and require less current, you also need smaller cables and smaller cables means less cost, less weight in the vehicle. It is also easier to assemble [the modules] in the vehicle.” Steffen adds: “Through reduced weight and increased regenerative braking, the range and the efficiency of the vehicle can increase by about 3%. For a typical vehicle, this translates into about 10 miles (16 km) more range.” Driver anxiety in relation to the distance a BEV can drive between charges is one of the biggest hurdles in their acceptance among consumers and key to next-generation models. A small 800-volt enabled module, as used by Drivemode, frees up additional space that not only benefits internal passenger and storage possibilities, but also enables the placement of additional batteries in order to extend range in BEVs. Read the full article on: http://drivemode-h2020.eu/silicon-carbide-sic-devices-for-the-next-generation-of-electric-vehicles/
Keywords
electric cars, Silicon carbide, battery electric vehicles, energy, advantages