Modeling of silicon carbide (SiC) power devices for electronic switching in low voltage applications

Owing to their robust behavior silicon carbide semiconductor power devices can be used advantageously to protect a circuit from high short circuit currents. Due to their superior properties they have the potential to be widely used in low voltage networks (up to 1000 V a.c.) as an electronic load feeder to electronically switch ohmic-inductive loads such as motors or electric heaters. Because of their specific on-resistance which is reduced in comparison to equivalent conventional power devices based on silicon the on-state losses are much closer to those of mechanical contacts. Thus, power dissipation of switchgear and switchboards is in the range of that of mechanical switches. In the field of electronic switching technology, we distinguish between AC51 and AC53 utilization category. Whereas AC51 characterizes ohmic loads, e. g. electric heaters, AC53 describes make and break operations with induction motors whose starting current amounts from 4 to 9 times the rated current. In the present paper a model is introduced to anticipate the performance as well as to describe the electrical and thermal behavior of SiC-power devices during short circuit operation and when conducting the rated current in both, AC51 and AC53, modes. The results obtained from this model agree very well with measurements performed on an ohmic-inductive circuit. The model can be used to develop a special tool for circuit simulation systems such as PSPICE.