A Corrected method for Calculation of Failure Rate Based on IEC-TR-62380

Abstract

In this paper an optimized way of failure rate and mean time between failure evaluation can be used in the multilevel inverters is proposed. Actually, There are two main references, MIL-HDBK and IEC handbook, used for failure rate calculation. Considering this, lots of literatures used to use MIL-HDBK for failure rate analysis. However, According to the comparison having been done in this paper, some effective parameters are not considered in the MIL-HDBK standard, and these parameters are included environmental conditions, package type and operation time. Therefore, the calculation results of the failure rate and MTBF based on MIL-HDBK are not accurate. In this paper, an improved method in which the most important parameters effective on the failure rate and MTBF are considered by considering the IEC handbook as the main standard for calculation. Because of this point that the IEC handbook standard considers environmental conditions, package type and operation time for each component, the calculation results based on the standard are more precise than MLL-HDBK one. Apart from that, for calculation of the either conduction loss or switching loss, a precise method is used because most of the published papers used a conventional method for power calculations, and that is why temperature and failure rate calculations in those papers are not accurate enough to be able to calculate junction temperature, failure rate, and MTBF correctly. Eventually, the presented method is evaluated by a five-level NPC simulation in the PLECS software. Finally, theoretical and simulation results of the conduction and switching losses are very close to each other.