Reliability Analysis of a High-Efficiency SiC Three-Phase Inverter

Silicon carbide as an emerging technology offers potential benefits compared with the currently used silicon. One of these advantages is higher efficiency. If this is targeted, reducing the on-state losses is a possibility to achieve it. Parallel-connecting devices decrease the on-state resistance and therefore reduce the losses. Furthermore, increasing the amount of components such as parallel connection of devices introduces an undesired tradeoff between efficiency and reliability, since an increased component count increases the probability of failure. A reliability analysis has been performed on a three-phase inverter rated at 312 kVA, using parallel-connected power modules. This analysis shows that the gate voltage stress has a high impact on the reliability of the complete system. Decreasing the positive gate-source voltage could, therefore, increase the reliability of the system approximately three times without affecting the efficiency significantly. Moreover, adding redundancy in the system could also increase the mean time to failure by approximately five times.