Ruggedness of 6.5 kV, 30 a SiC MOSFETs in extreme transient conditions

Abstract

6.5 kV silicon IGBTs are used in multi-megawatt medium voltage power converters for rail traction applications, AC drives and grid-connected power converters. The 6.5 kV, 30 A SiC MOSFETs, recently launched by Wolfspeed, have the potential to replace Si IGBTs. Static and dynamic characteristics of the 6.5 kV SiC MOSFETs have been reported earlier. During the extreme transient conditions, the SiC MOSFETs can be subjected to high voltage overshoot and high short circuit current. In this work, ruggedness of these MOSFETs is established by short-circuit tests and single shot avalanche tests at room temperature. The 6.5 kV SiC MOSFET is observed to withstand 7.75 J of short-circuit energy at 20 V gate voltage with a stress withstanding time of 6 μs. The single shot avalanche test result shows an avalanche energy of 5.0 J. The increase in junction temperature of the SiC MOSFET at the avalanche failure is estimated from the experimental results.