AC Power Cycling Test Setup and Condition Monitoring Tools for SiC-Based Traction Inverters

Abstract

AC power cycling tests allow the most realistic reliability assessment by applying close to real stress to the device or module under test to meet functional safety standards, which is highly critical for traction applications. This paper presents a comprehensive guideline and shares critical know-how to develop a 120 KVA AC power cycling test setup for high-power Silicon Carbide (SiC) modules. As of today, traction applications can not generate an early warning signal for drivers to replace critical components on time. For this purpose, the suitable precursors for all dominant failure mechanisms are discussed, and the corresponding condition monitoring tools are proposed to monitor the device aging on power converters. These condition monitoring tools are integrated into the built-in desaturation protection circuit of the electric vehicle (EV) gate driver for low-cost, practical implementation. The on-resistance of all twelve switches is monitored online as a temperature-sensitive electrical parameter (TSEP) to measure the junction temperature of the devices. To avoid heavy processing load in the microcontroller, the out-of-order equivalent time sampling technique is developed for data sampling, which leads to a measurement error of less than 1.5%. In addition, the design considerations regarding common mode noise and aging effect on DESAT protection are investigated, and experimental findings are presented.