Papers by Keyword: Reliability

Abstract: Recently, silicon carbide (SiC) power modules of the 3.3 kV voltage class became available and are a promising candidate to replace silicon power modules in traction applications. However, the more than three times higher Young’s Modulus compared to silicon leads to a reduced lifetime under thermo-mechanical stress. This could pose a significant obstacle in their implementation, since traction applications are particularly demanding in their mission profiles with respect to load cycling, but also to environmental conditions. Thus, the thermo-mechanical stress is not just limiting the lifetime itself, but might also promote the humidity induced degradation due to delamination or micro-cracks. In this work, multiple power cycling tests at different temperature swings on 3.3 kV SiC MOSFET chips in a power module were performed, to assess their ruggedness under thermo-mechanical stress. Before or afterwards, these modules were tested under standard HV-H3TRB conditions to verify the interaction between thermo-mechanical and humidity stress on the robustness of the modules.

Abstract: This paper provides an experimental investigation through infrared thermography of the steady-state temperature imbalance arising in parallel SiC MOSFETs. A switched-mode boost power converter based on two arrays of 4 parallel 1.2 kV MOSFETs is selected as a case-study. The analysis aims at proving that a proper device arrangement can minimize the thermal imbalance in the absence of circuit layout optimization.

Abstract: Silicon carbide (SiC) metal-oxide-semiconductor field-effect transistors (MOSFETs) are successfully replacing traditional silicon insulated gate bipolar transistors (Si IGBTs) in power applications. Nonetheless, two crucial challenges persist: gate-oxide reliability and a reduced short circuit (SC) withstand time. This paper explores a novel MOSFET structure, which is designed to address these concerns and compares it with existing designs through extensive 3D TCAD simulations. The proposed MOSFET structure features a p-region under the gate, providing a unique configuration for improved performance during SC events. This novel structure is then compared to two commercially realized MOSFET structures. Our structure has a superior on-state performance with a specific resistance of 1.48 mΩ /cm², showing an improvement by 25 % and 15 %, respectively. It also increases the blocking capability by 100 V and SC withstand time in comparison to the double-trench MOSFET.

Abstract: The main objects of the EES, the service life of which exceeded the standard value, are increasingly beginning to determine the efficiency of work every year. This manifested in an increase in the number of automatic emergency shutdowns, the number and complexity of emergency-hazardous defects. Organization of operation, maintenance and repair of these facilities recommended carried out according to their technical condition. And since the technical condition determines the reliability and safety of the object, it is therefore recommended to take these properties into account more fully. These recommendations in the EES carried out at a high quality level, intuitively, according to operating experience.In this article, as distributed objects of continuous operation, overhead power transmission lines (OPTL) with a voltage of 110 kV and higher, the service life of which exceeds the standard value, are considered. The issues of quantifying the degree of significance of the aging problem for a set OPTL, their classification and methodology for assessing the difference in the degree of aging when classifying them according to given types of characteristics are considered. The methodology and algorithm of methodological support for the management of the EES and network enterprises during the organization of operation, maintenance and repair, been developed.

Abstract: Resistance spot welding (RSW) is a commonly used process in a variety of fields such as automotive, aerospace, household, furniture, and railway for welding sheet metal parts. These industries further demand a welding machine that is portable and versatile in terms of where it can be utilized, such as, among others, remote locations, and is cost and energy-efficient, reliable, and highly efficient performance-wise. With this aim, the work develops a portable spot-welding machine with specific specifications, of an electrode of 0.394 inches in diameter and 10 inches in length, made of copper, and transformer specifications of 6 V-1500 A with 7 variable current settings. This machine is designed to provide accurate, consistent, and reliable welding readings. Additionally, the machine works on an AC supply of 220 volts, making it easily usable. The machine is found to be cost-effective, with a development cost of only 6100 rupees. It has also been found to be reliable and effective in welding up to two 3 mm mild steel plates under different currents, resistivity, and voltage settings. The machine is simple to operate and user-friendly and with a compact and lightweight design, it is highly versatile and easy to operate for a wide range of welding applications.

Abstract: This study focuses on the design and construction of an improved crushing machine with a capacity of 0.15 (150 kg/hr) tons per hour, 15 Hp, and 2910 rpm speed. The design follows criterion design guidelines to ensure the improved service life of the component. When the values produced from the current design approach were contrasted with the values and outcomes received from the analysis using the Ansys package, the design should be reliable. The hammers produced are subjected to carburisation process using bio-wastes such as coconut shells, saw dust, and palm kernel shells to enhance the reliability of the machine. The bending of the shaft is controlled during the rotation at rated speed rpm when a load is applied to the shaft. The critical speed of the shaft is experienced with deflection when the shaft rotates freely. The natural frequency and speed were put under check in order to avoid failure. The von Mises stress was employed as a yielding criterion for the shaft. It states that if the components of stress operating on a body are more than the criterion, the body will yield.

Abstract: This work addresses the challenges associated with the development of short neutral sections (SNS) for overhead lines of high-speed moving trains. A crucial function of a short neutral section is to provide electrical isolation between the different phases of AC traction. These sections are typically located in proximity to the traction substation and sectioning posts. The current SNS design presents several issues, including pantograph arcing, wear and tear of the overhead line system, and the need for manual rotation during periodic maintenance. To address these challenges TRIZ is used, a problem-solving methodology that leverages inventive principles to generate innovative solutions. The work outlines the use of several TRIZ tools and techniques, including the Interaction Matrix, Functional Analysis, Function-Body Diagram (FBD), Trimming, and the Contradiction Matrix [1]. With the application of these tools, the author presents several potential solutions for improving the SNS design to eliminate periodic maintenance and services. One proposed solution involves the use of a segmented overhead line system with an insulating cylinder-shaped discrete insulator to ensure smooth contact of the pantograph. Another solution involves the use of a twisted strip-based insulator to replace linear motion with rotating movement, eliminating the need for manual rotation. The work emphasizes the importance of considering various factors, such as design, material, wear rate, maintenance, and creepage distance, when evaluating the feasibility of these solutions. By leveraging TRIZ to generate innovative solutions, the author demonstrates the potential of this methodology to drive innovation and overcome complex challenges in the development of short neutral sections for high-speed rails.

Abstract: This study presents the results of visual and infrared (IR) inspection of photovoltaics (PV) technologies installed at the Qatar environment and energy research institute (QEERI) outdoor test facility (OTF) at Qatar Foundation (Doha, Qatar). Silicon based PV technologies which have been operational in the field since 2014, have been investigated for various failure modes. The visual inspections were carried out for all the PV modules from the backside however, the inspection from the front side was not possible for some modules due to heavy soiling. The visual defects which were identified during this study include, cracking of the back glass, yellowing of the encapsulant material, cracks formation in the back sheet, and pits formation in the back sheet. The visual inspection revealed that around 19 % of the total modules have back sheet cracking and discoloration, 8 % have yellowing of the encapsulant, and around 4 % were having pits in the back sheet. Moreover, one module was detected with back glass cracking. The IR inspection was also done both from front and backside for all the silicon PV modules to detect hot spots. The IR inspection has revealed that hot spots were generated at different locations of the PV modules. 39 % of the modules have hot spots at the location of junction boxes, around 6 % of the modules have hot spots in junction boxes and around 1 % have hot spots at the locations away from junction boxes. The visual and IR inspection has revealed that the dominant failure modes which have been observed for silicon-based technologies at OTF are the hot spots generation at junction boxes and the back sheet cracking, and its yellowing.

Abstract: The demand is rapidly increasing for SiC MOSFETs and diodes for power electronic conversion semiconductor (PECS) applications such as electrified vehicle charging and traction, energy storage systems and industrial power supplies. These applications employ a high quantity of large-area die per system while demanding high system-level reliability under aggressive electrical and environmental operating conditions. In addition, SiC devices exhibit some failure mechanisms that are less severe than, or non-existent, in Si devices. This situation demands thorough and novel device reliability characterization and quantification. It is also driving the development of industry consortia standards and guidelines at a much faster rate, and relatively earlier in the technology maturation phase, than occurred in the Si industry. In this paper, I will review some of the key published reliability performance data, stress procedure methodologies used, and implications for key applications. I will also compare and contrast the existing guideline and standard documents and suggest directions that are being explored for future documents. I will also discuss how future guidelines and standards are being developed to cover the SiC-specific failure mechanisms for representative mission profiles for some key applications, particularly electrified vehicles.

Abstract: Silicon carbide (SiC) MOSFETs are gaining more and more market share in typical silicon (Si) IGBT applications such as traction or renewable energies. Especially in reliability sensitive traction applications, medium voltage IGBT-modules (3.3 kV-6.5 kV) are widely used and introducing SiC-MOSFETs to such industries is the next self-evident step already on the way. While their superior electrical performance has been generally accepted already (e.g. [1]), SiC-modules have not yet established a track record of high reliability in this voltage class. For this study, 3.3kV SiC-MOSFET-switches were compared to standard Si-IGBTs regarding their humidity robustness under high voltage bias. Both chip types had been assembled in the same traction rated packages to exclude this influence. The Si-IGBTs resembled the well-known industry standard performance, while the SiC-MOSFETs show no degradation within the reported test time of 2000 h. Given the fact [2], that the latest Si-IGBT generation offers a much better humidity performance as well, the standardised HV-H³TRB is no longer sufficient to provoke failures within a reasonable testing time. On the one hand, this suggests that humidity driven failures will not be an issue under field conditions anymore. On the other hand, even harsher tests are required to investigate differences in humidity performance.