Recent Advances in Power Electronics and the Differences Between SiC and IGBTs in Electric Vehicles
In 2022, the use of silicon carbide in China is of great importance, mainly due to the many changes brought about by the current 800V system. According to the materials I have analyzed, I would like to discuss with you the specific differences in various aspects.
First of all, let’s talk about IGBT. In the field of electric vehicles, we should be grateful to Infineon for their contribution. Before European automakers entered the market, Nissan, Honda, and Toyota developed their own inverters based on their technologies, with the cooling and iteration technologies of IGBT as the core. Before importing SiC, Tesla also used a single IGBT tube to achieve high-power drive. After Infineon developed the standard package 6in1 IGBT, the difficulty of inverter development was greatly reduced.
In the design of high-power inverters, Tesla engineers used a discrete single-tube parallel, built-in single-tube heat dissipation and cooling technology, as well as power layering busbar technology to increase the power of the inverter, but the assembly process was quite complicated. So in the iterative process, Tesla was the first to directly iterate into SiC in its 400V products, as shown in the graph below:
Power density and efficiency:
Of course, the efficacy of the inverter itself is mainly benchmarked based on parameter specifications, as shown in the table below:
In other words, the efficiency brought by the 400V SiC has yet to be achieved by many subsequent vehicles. Similar vehicles like Lucid Air can also achieve relatively high Mile/kWh.
The graph below shows a comparison of inverter efficiency under two different working conditions, UDDS and HWFET, with dynamic characteristics. The difference in efficiency is between 4% and 7%.
Note: This data is provided by FEV and is based on abstracted data for comparison purposes.
In other words, there is indeed a significant difference in efficiency between simulation and actual testing.
Therefore, there is an 8% efficiency difference between the two systems, with 2% at the charging level and 6% at the operating level. For a battery of equal size, especially a fast-charging battery of 100-120 kWh, the net benefit could be weighted as 8-10 kWh, corresponding to approximately 6,400-8,000 RMB at 0.8 yuan/Wh.
In the long run, not only the cost benefit, but also high-capacity batteries need the support of SiC to achieve high range and efficiency.
In summary, although the efficiency difference of silicon carbide is not large, it has significant improvements in large-capacity batteries. Next, we will focus on the packaging of SiC modules when we have time.
This article is a translation by ChatGPT of a Chinese report from 42HOW. If you have any questions about it, please email bd@42how.com.