Reliability Evaluation of Liquid and Polymer Aluminum Electrolytic Capacitors

Liquid aluminum electrolytic capacitors are known for their reliability problems. They are considered as the weakest link in the power electronics system. The liquid electrolyte of these capacitors is the single most important component which affects the reliability of these capacitors. The principal ingredients of the liquid electrolyte are solvent, water, solute and additives such as corrosion inhibitors and hydrogen absorbers. Usually, the primary solvent used in liquid electrolyte of aluminum electrolytic capacitors is ethylene glycol or γ-butyrolactone. The effect of liquid electrolyte solvent on the failure mechanisms observed in liquid aluminum electrolytic capacitors is missing. Effect of ripple current on the observed failure mechanisms is unknown. Polymer aluminum (PA) capacitors were introduced as the polymer electrolyte is conductive and solid therefore, it does not evaporate and the equivalent series resistance (ESR) of the PA capacitors is low. Manufacturers advise not to use PA capacitors in elevated temperature-humidity environments. But, the Failure modes and mechanisms of polymer aluminum electrolytic capacitors in elevated temperature-humidity are unknown. In this study, life testing of liquid aluminum electrolytic capacitors chosen based on primary solvent of the electrolyte was performed. For γ-butyrolactone solvent based capacitors, the failure mechanisms observed causing decrease in capacitance were evaporation of electrolyte and decrease in surface area of the aluminum oxide dielectric layer. The observed ESR increase was due to evaporation of electrolyte. For ethylene glycol solvent based capacitors, ESR increase was observed due to ester and amide formation, along with decrease in concentration of the carboxylic acid salts in the electrolyte and evaporation of electrolyte. The failure mechanisms observed in life tests with and without ripple current were the same. PA capacitors were tested at elevated temperature-humidity of 85ºC, 85%RH and Highly Accelerated Stress Test (HAST) condition of 110ºC, 85%RH. PA capacitors failed due to increase in ESR and increase in leakage current. Iron particles in dielectric layer from the manufacturing process of PA capacitors caused the high leakage current failure. This is a new failure mechanism which has not been reported in the literature. Failure modes observed in 85ºC, 85%RH and HAST tests were same therefore, HAST tests can be used as rapid assessment test for PA capacitors in elevated temperature-humidity environment

Particle Filter-Based Prognostics for an Electrolytic Capacitor Working in Variable Operating Conditions

International audiencePrognostic models should properly take into account the effects of operating conditions on the degradation process and on the signal measurements used for monitoring. In this work, we develop a Particle Filter-based (PF) prognostic model for the estimation of the Remaining Useful Life (RUL) of aluminum electrolytic capacitors used in electrical automotive drives, whose operation is characterized by continuously varying conditions. The capacitor degradation process, which remarkably depends from the temperature experienced by the component, is typically monitored by observing the capacitor Equivalent Series Resistance (ESR). However, the ESR measurement is influenced by the temperature at which the measurement is performed, which changes depending on the operating conditions. To address this problem, we introduce a novel degradation indicator independent from the measurement temperature. Such indicator can, then, be used for the prediction of the capacitor degradation and its RUL. For this, we develop a Particle Filter prognostic model, whose performance is verified on data collected in simulated and experimental degradation tests

원자력 납품 체계: 한국 원자력 발전소의 부정 부품

학위논문 (석사)-- 서울대학교 대학원 : 에너지시스템공학부, 2015. 2. 황일순.In May 2013, it turned out that a few items were supplied to NPPs with fraudulent certificate. The documents were the reports of verification - Quality Verification Document (QVD), Equipment qualification (EQ), and Commercial Grade Items Dedication (CGID) - which are required to submit when suppliers deliver the items to the operator. The fraudulent documents were the result of collusion between suppliers and certificate authorities. As the unqualified items were detected, operators had to halt the operation and delay the construction of NPPs for the replacement of fraudulent items and inspection on overall facilities. As the result, power reserve level dropped significantly and rolling blackouts were conducted, which led to economic loss of industry. In addition, the disclosure of fraudulent items acted as the catalyst for the public negativity which has been grown since Fukushima Daiichi nuclear accident. These unqualified items are dealt with the concept of Counterfeit, Fraudulent, and Sub-standard Items (CFSIs). CFSIs are detected in various components of NPPs, and these could be direct factors of accidents, such as reactor shutdown, unanticipated release of radioactive materials, and damage of fuel. CFSIs also have the potential to degrade the performance of safety functions and safety-related system. Since 1980s, regulations on CFSIs were first developed in USA, and currently adopted globally. However, in Korea, the CFSIs had not been considered as a significant issue, and meanwhile, CFSIs occurred. The purpose of research is to define the root cause of CFSIs and suggest policy recommendations as solutions. For the comprehensive research of nuclear procurement system, three different methodologies were appliedthe analysis on Korean laws and regulations, interviews on the subjects of nuclear procurement, and statistical analysis on contracts between suppliers and operators. According to Nuclear Safety Law, regulatory authority has a duty to inspect on operators, suppliers, and certificate authorities, regarding to quality assurance. The laws and regulations were well-organized to prevent the CFSIs. Therefore, interviews were conducted to figure out the inherent issues, and following problems were pointed outshortage of manpower for verification and independence of certificate authorities. In addition, statistical analysis on bidding and contract procedures were conducted to understand the issues. First of all, it was recognized that bidding processes were delayed up to 5 weeks, without extending the deadlines for supply, as the compensation of delay. Moreover, in a few bidding processes, procedures were ignored at all. Based on the analysis on the laws and regulations, interviews, and statistical analysis, nuclear procurement system was modeled. System dynamics was taken as the methodology to find out the interrelation between various factors. In the early of NPPs operation, the investment had been concentrated on safety issues, and as the result, the operating hours were increased consistently. However, when the operation of NPPs became stable with barely no safety issues, the operator has decreased planned maintenance period for stable power generation. The reduced period was a burden to suppliers, because the deadlines for supply are cut down. Accordingly, it caused the CFSIs in NPPs. Another aspect shown in the nuclear procurement system is the concern on quality control. If there are a number of safety issues, quality control is conducted intensively, which lead to reduction of CFSIs. However, because the safety-related issues barely occurred since 1990s, the control on CFSIs couldnt be conducted properly. The requirement of registration for suppliers is another factor of CFSIs. During the bidding, open tendering with the lowest price is performed for the profit of operators. Thus the fewer suppliers apply, the more income they get. To keep other competitors from applying, suppliers pushed operator to maintain the high requirement and the small number of suppliers was preserved. But it induced the delay on bidding process. It caused suppliers not to have enough time for verification and became the reason for the CFSIs. In addition, the confined pool of suppliers made operators to involve vendors and foreign countries into the supply chain. The extension of supply chain disturbed quality control, which led to CFSIs. Finally, the number of certificate authorities could be the reason of CFSIs. In the case of QVD, since the private authorities could be qualified to conduct verification, the number of authorities have increased up to 2500. The competition among them became fierce, so that suppliers could exert power over certificate authorities. It undermined the independence of certificate authorities and led to the corruption during the verification procedure. On the other hand, in the case of CGID, there is only one domestic certificate authority. It made the time for verification to be extended, which also induced the CFSIs. As the solutions to the four mentioned problems, policy recommendations were suggested in the aspect of operator, supplier, regulatory authority, and certificate authorities. First of all, operators need to adopt a storage inventory management. Foreign operators have developed various researches for inventory management. However, Korean operator doesnt have such program because of insufficient budget. If the inventory management could be conducted properly, operators could guarantee the deadlines for supply, and quality assurance also could be conducted in comprehensive way. Operator should alleviate the standard for suppliers, and allow more suppliers to register. It reduce the period of bidding procedure. In addition, government should support the control of CFSIs by supplementing manpower for certificate authorities, reinforcing specialty, and establishing institution for verification. Certificate authorities for QVD should secure their independence and perform verification procedure properly by reducing the number of authorities through the reinforcement of standard for themselves. In case of CGID, the establishment of domestic certificate authorities should be promoted. It will decrease the time for verification and CFSIs also will be reduced.Chapter 1 Introduction 1 1.1 Background 2 1.2 Objective 8 Chapter 2 Review of the State of the Art 10 2.1 Example of CFSIs 10 2.2 CFSIs impact on safety 26 2.3 Integrated management system requirements 28 2.4 Procurement scenarios 37 2.5 Establish quotations or bids 40 Chapter 3 Research Design 46 3.1 Research questions 46 3.2 Methodology 49 3.3 Case selection 57 Chapter 4 Analysis of Nuclear Procurement System in Republic of Korea 61 4.1 Laws and regulations on nuclear procurement 61 4.2 Interview on subjects of nuclear procurement 65 4.3 Statistical analysis on nuclear procurement system 67 Chapter 5 Nuclear Procurement Model 76 5.1 Safety improving feedback 76 5.2 Planned maintenance feedback 80 5.3 CFSIs manufacturing feedback 84 5.4 Quality control feedback 86 5.5 Lowest bidding feedback 88 5.6 Certificate authority feedback 90 Chapter 6 Policy Recommendation on Nuclear Procurement system in Republic of Korea 93 6.1 Operator 93 6.2 Supplier 98 6.3 Regulatory Authority 98 6.4 Certificate Authority 99 Chapter 7 Conclusion 102 7.1 Summary and findings 102 7.2 Future work of dissertation 105 Appendix 107 Bibliography 117 초 록 124Maste

A Solder-Defined Computer Architecture for Backdoor and Malware Resistance

This research is about securing control of those devices we most depend on for integrity and confidentiality. An emerging concern is that complex integrated circuits may be subject to exploitable defects or backdoors, and measures for inspection and audit of these chips are neither supported nor scalable. One approach for providing a “supply chain firewall” may be to forgo such components, and instead to build central processing units (CPUs) and other complex logic from simple, generic parts. This work investigates the capability and speed ceiling when open-source hardware methodologies are fused with maker-scale assembly tools and visible-scale final inspection. The author has designed, and demonstrated in simulation, a 36-bit CPU and protected memory subsystem that use only synchronous static random access memory (SRAM) and trivial glue logic integrated circuits as components. The design presently lacks preemptive multitasking, ability to load firmware into the SRAMs used as logic elements, and input/output. Strategies are presented for adding these missing subsystems, again using only SRAM and trivial glue logic. A load-store architecture is employed with four clock cycles per instruction. Simulations indicate that a clock speed of at least 64 MHz is probable, corresponding to 16 million instructions per second (16 MIPS), despite the architecture containing no microprocessors, field programmable gate arrays, programmable logic devices, application specific integrated circuits, or other purchased complex logic. The lower speed, larger size, higher power consumption, and higher cost of an “SRAM minicomputer,” compared to traditional microcontrollers, may be offset by the fully open architecture—hardware and firmware—along with more rigorous user control, reliability, transparency, and auditability of the system. SRAM logic is also particularly well suited for building arithmetic logic units, and can implement complex operations such as population count, a hash function for associative arrays, or a pseudorandom number generator with good statistical properties in as few as eight clock cycles per 36-bit word processed. 36-bit unsigned multiplication can be implemented in software in 47 instructions or fewer (188 clock cycles). A general theory is developed for fast SRAM parallel multipliers should they be needed

Investigation of Volatile Organic Compounds (VOCs) released as a result of spoilage in whole broccoli, carrots, onions and potatoes with HS-SPME and GC-MS

Vegetable spoilage renders a product undesirable due to changes in sensory characteristics. The aim of this study was to investigate the change in the fingerprint of VOC composition that occur as a result of spoilage in broccoli, carrots, onions and potatoes. SPME and GC-MS techniques were used to identify and determine the relative abundance of VOC associated with both fresh and spoilt vegetables. Although a number of similar compounds were detected in varying quantities in the headspace of fresh and spoilt samples, certain compounds which were detected in the headspace of spoilt vegetables were however absent in fresh samples. Analysis of the headspace of fresh vegetables indicated the presence of a variety of alkanes, alkenes and terpenes. Among VOCs identified in the spoilt samples were dimethyl disulphide and dimethyl sulphide in broccoli; Ethyl propanoate and Butyl acetate in carrots; 1-Propanethioland 2-Hexyl-5-methyl-3(2H)-furanone in onions; and 2, 3-Butanediol in potatoes. The overall results of this study indicate the presence of VOCs that can serve as potential biomarkers for early detection of quality deterioration and in turn enhance operational and quality control decisions in the vegetable industry