Browsing by Author "Ali, Syed Huzaif"
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Item Analysis of Vₜₕ Variations in IGBTs Under Thermal Stress for Improved Condition Monitoring in Automotive Power Conversion Systems(Institute of Electrical and Electronics Engineers Inc, 2018-11-12) Ali, Syed Huzaif; Ugur, Enes; Akin, Bilal; 0000-0001-6912-7219 (Akin, B); Ali, Syed Huzaif; Ugur, Enes; Akin, BilalToday, power conversion in automotive industry depends heavily on the reliable operation of insulated-gate bipolar transistors (IGBTs). Condition monitoring of IGBTs and reporting imminent faults to driver dashboard are critical for avoiding any fatal accidents. In this study, first, a comprehensive comparison is carried out between on-state collector-emitter drop (V_{ce,on}) with gate threshold voltage (Vₜₕ), as two reliable aging precursors. In order to enrich current understanding of IGBT aging prognosis, accelerated aging methods are applied under a wide variety of thermal stresses. Aging mechanisms and physical phenomena responsible for variation in both V_{ce,on} and Vₜₕ have been methodically investigated. These explanations are also supported by detailed failure analysis. Based on the extensive result sets for tested samples from different manufacturers with different structural types, it is found that V_{ce,on} show different trends at different stress levels, whereas under the same test conditions Vₜₕ provides more consistent and robust state-of-health information. Finally, an example experiment has been performed in which continuous V_{ce,on} measurements coupled with Vₜₕ information has been used to provide more insight about the device aging as well as faults in an automobile's sub-systems.Item Condition Monitoring for Discrete Packaged Insulated Gate Bipolar Transistors in Power Converters(2018-08) Ali, Syed Huzaif; 0000-0002-2425-1475 (Ali, SH); Akin, BilalExtensive utilization of insulated gate bipolar transistor (IGBTs) in the power converters has significantly increased concerns over its reliability. Failure of such critical component eventually cause unexpected shut downs and even lead to catastrophic faults resulting in huge economic loss. So, tools for incipient fault diagnosis and aging prognosis have to be utilized for reducing the risk of faults and accidents. Yet, established tools are not mature enough and there exist a major reliability gap exist in condition monitoring of IGBTs. In order to improve current prognostic and diagnostic tools, this dissertation investigates ongoing aging induced degradation and corresponding shifts in electrical parameters for IGBTs. Such useful electrical parameters are referred as aging precursors which are obtained after extensive thermal aging tests. Based on the aging test results, aging precursors are identified and an in-situ condition monitoring circuit has been proposed as well. Due to low component count, the proposed circuit is cost effective and can be easily integrated to conventional gate driver circuits. Based on the data measurements, further remaining useful lifetime estimation for IGBTs have been carried out as well. It is conceived that such tools lay foundations for smart-energy conversion systems which are self-capable in evaluating the degradation information using aging precursors to prevent imminent failures in the system. Briefly, this dissertation discusses: o identification and characterization of aging precursors, o development of innovate and easy-to-integrate condition monitoring circuit o development of remaining useful lifetime estimation tool based on the monitored data for advancing smart power conversion systems.