Railway traction reliability

This paper discusses the commonly accepted method for life-time prediction for power converters in traction. The method is based on junction temperature estimation and thermal cycles on a given duty cycle. The predicted numbers of thermal cycles are compared to the curves giving the number of cycles to failure versus temperature cycles. These curves are extrapolated from power cycling tests. Power cycling tests and extrapolation method will be discussed, particularly under the aspect of failure mechanisms that are induced. There is a trend to increase the operational junction temperature of semiconductor device, this trend impose to find some new assembly technologies supporting higher thermal constraints. The impact for the design of power converter is also discussed.