Online Health Monitoring and Aging Prognostics for SiC Power Converters

The 650 V and 1200 V SiC MOSFETs have gained significant market acceptance in the recent years, mainly, due to the promise of higher power conversion efficiency and power density. However, the lack of field-proven long-term reliability data of SiC MOSFETs is still a major concern, particularly in applications where the devices are exposed to harsh thermal and electrical cycles. This paper discusses a methodology to monitor health status of SiC MOSFETs to enable aging prognostics and remaining useful life estimation. The methodology is based on measurements of ohmic resistance between source and drain terminals. In order to desensitize the method from the well-known temperature dependency of the Rdson; it is proposed to measure the resistance of the MOSFET’s body-diode. It will be shown that body-diode presents a much lower dependency to changes in temperature. The measurements can be obtained in real-time, without interrupting the converter normal operation, a highly appreciated feature in next generation of power electronics converters. By proper management of failure precursor data, it will be possible to forecast converter failures so that necessary actions can be taken before a catastrophic failure occurs. The methodology is applicable for SiC MOSFETs of any voltage class from 650 V to 15 kV.