I. INTRODUCTION
T HE reliability and failure study of individual components
used in power converters has been well conducted and can
be found in literature [1]–[4]. A bathtub curve of the failure
rate is the most accepted model for any electronic component
[5], [6], and this curve is shown in Fig. 1(a). The infant
failure of the components is generally linked to poor design,
poor installation, or misapplication, and a constant failure rate
defines the useful lifetime of the component. However, several
disagreements with the bathtub curve have been presented in