Short Circuit Robustness for Traction Inverters from an Application Point of View

Abstract:
SiC MOSFETs haven proven a large potential of energy savings, especially in the V(DS) = 1200 V volt-age class. In automotive drive applications, robustness for short-circuit events is mandatory, which is often primarily defined by a short-circuit withstand time t(scwt). During the last decade, t(scwt) was reduced in each IGBT generation down to ≈3 mus. Nowadays, t(scwt) for SiC MOSFETs is in the range from 1 to 5 mus, depending on test conditions which must be covered for all operating points. Step by step, we separate a short-circuit event into different phases from turn on until detection and finally turning off the current. While reducing the application-required t(scwt), the blanking time and turn-off time become dominant factors, and the gate driver delay time t(delay) becomes a minor factor. In an example we show, depending on the gate driver IC a reaction time t(react) of 890 ns to 930 ns under real application condi-tions and parameter variations can be achieved resulting in a required t(scwt) between 1.2 mus and 1.3 mus for the applied SiC MOSFETs.