System-level reliability testing a frequency converter with simultaneous stresses

Because the time available for product design is usually much shorter than the projected operating life of the product, accelerated stress testing is commonly used to study the reliability of components, devices or larger systems. Under normal use conditions, products can be subjected to multiple simultaneous stressors. Consequently, it is also useful to use concurrent stresses during reliability testing. However, the combinatory effects of multiple stressors can be quite complex, which complicates failure analysis after testing. The usage of concurrent environmental stresses as a system-level reliability testing method is studied with the help of a frequency converter. The effects of different stresses on the failure modes and on the overall testing time were examined separately and simultaneously. The results show that with concurrent stresses the same kind of failure modes may be observed during testing as in normal service conditions and, more importantly, a significant reduction in testing time could be achieved when compared to that of single stress tests.