Current Overload Research Articles

RFID Assisted Intelligent Vehicle Communication Management System

RFID is an important technology in the Internet of things that has the characteristics of safe, affordable, efficient, which received widespread attention and research. This paper proposes a UHF RFID-based intelligent vehicle management system (the Internet). The system consists of RFID hardware system, CDMA system, the GIA system, data processing system, and can realize intelligent vehicle identification, location, tracking, velocity measurement, monitoring and management, to address the current severe road congestion, speeding, vehicle theft and vehicle overload management and other issues. Software and hardware design of intelligent vehicle management system based on RFID, focuses on systems, security design, selection of RFID cards and vehicle access control software features, the fleet management system is not only convenient, but also intelligent identification of vehicles and vehicle theft, in the community, school, car park and vehicle management occasions has a good application.

Study of Heat Localization in HTS Wires at Overload Conditions

A common problem of superconducting devices is to survive during a fault with a current overload. At a fault, superconducting device will have strong overheating and burning out is possible. The problem becomes more serious in case if a high-temperature superconducting (HTS) wire has a weak point where the critical current is less than the average over a wire. Such a weak point could be the point of origination of strong overheating within a very localized area. This can lead to burning and destroying of an HTS device. To study this problem, we developed the experimental setup with the spatial resolution 2 mm and the time resolution 1 ms to observe a local temperature/voltage evolution in HTS tapes overloaded by currents. The preliminary experiments were performed to measure local heat/voltage development on 2G HTS tapes with an artificial weak point. Local heat/voltage evolutions have been measured and compared with calculations by our model developed earlier.

A Medium-Voltage Medium-Frequency Isolated DC–DC Converter Based on 15-kV SiC MOSFETs

In this paper, a novel isolated dc-dc converter topology for medium-voltage (MV) applications is proposed by combining the advantages of resonant converters and dual active bridge (DAB) converters. In normal load scenario, this converter operates in an open loop resonant mode with a fixed switching frequency equals to the resonant frequency of the series resonant tank. Thus, zero voltage turn on at primary side and zero current turn off at secondary side are secured from zero to full load. When overload happens, the resonant capacitors will be clamped to the output voltage by the additional paralleled diodes. The proposed converter automatically switches to resonant and DAB mixed operation mode; therefore, the resonant current is naturedly limited. With zero to full load range soft switching and fast overload protection, the proposed topology is especially suitable for MV medium frequency applications utilizing high-voltage SiC MOSFETs. The converter operation modes are analyzed using time-domain waveforms and graphical state trajectory to derive the quantitative relationship between duty cycle, output voltage, and the overload current. Based on these relationships, a predictive duty cycle control is proposed to further limit the overload current of the resonant tank by sensing the output voltage. Combing the proposed topology and the predictive control, cycle-by-cycle overload and short-circuit protections are achieved. To fully utilize the capability of the 15-kV SiC MOSFET, magnetizing inductance, dead time, MV transformer, and resonant components are optimized with the operating range of 6-12 kV and 20-100 kHz. An experimental prototype running at 6 kV and 40 kHz is successfully tested with peak efficiency exceeding 98%. Test waveforms at no load and 10-kW full load validate the zero to full load range soft switching capability. Short circuit protection test demonstrates a 25-us overload protection speed.

A Study on the Local Characteristics by Wind & Solar Power on Korea Electric Power System

The importance of renewable energy sources are emerging and the proportion of renewable energy sources such as wind power and solar power properties with an intermittent output is expected to reach 30% in 2040 from 5% in 2015. For this reason, in order to increasing of renewable energy, flexible capacity service market will be expended. Therefore it needs to be evaluated local characteristics using voltage fluctuation, fault current, and line overload for understanding problem in power system. And it needs to strengthen. In this paper, based on “A study on the wind&solar power acceptable capacity of Korea Electric Power System on Frequency stability”, We considered local characteristics considering wind power and solar power generation and proposed complementary measures about problem.

Analysis of the Thermal Load of Structural Elements High-Power DC Supply with the Transformer of Ripple Filter with Current Overload

Design of the high-power DC supply quite logically based on the required electrical parameters and expected or defined operating conditions. A prerequisite trouble-free operation is also the correct choice of construction materials. Both in terms of mechanical strength and stability, and in terms of thermal load. The article deals with thermal conditions in the high-power DC supply with the transformer of ripple filter for long-term current overload.

Self-modulated field electron emitter: Gated device of integrated Si tip-on-nano-channel

We report the featured gated field electron emission devices of Si nano-tips with individually integrated Si nano-channels and the interpretation of the related physics. A rational procedure was developed to fabricate the uniform integrated devices. The electrical and thermal conduction tests demonstrated that the Si nano-channel can limit both the current and heat flows. The integrated devices showed the specialties of self-enhancement and self-regulation. The heat resistance results in the heat accumulation at the tip-apex, inducing the thermally enhanced field electron emission. The self-regulated effect of the electrical resistance is benefit for impeding the current overloading and prevents the emitters from a catastrophic breakdown. The nano-channel-integrated Si nano-tip array exhibited emission current density up to 24.9 mA/cm2 at a gate voltage of 94 V, much higher than that of the Si nano-tip array without an integrated nano-channel.

K10026 기반 스마트 플러그 시스템 개발 및 성능 분석

This paper proposes an effective smart plug system capable of monitoring power, cutting off standby power and overload current. The key design concept is focused on measurement accuracy, self power consumption and controlling via smart phone application. The system is composed of several plugs and a hub, and adopts a star-topology-styled TDMA wireless protocol for communication between plug and hub. The test result shows that the implemented smart plug system meets K10026 regulation and is worth in electrical safety, energy saving, easy living.

Integrated ZnO Nano-Electron-Emitter with Self-Modulated Parasitic Tunneling Field Effect Transistor at the Surface of the p-Si/ZnO Junction.

The development of high performance nano-electron-emitter arrays with well reliability still proves challenging. Here, we report a featured integrated nano-electron-emitter. The vertically aligned nano-emitter consists of two segments. The top segment is an intrinsically lightly n-type doped ZnO nano-tip, while the bottom segment is a heavily p-type doped Si nano-pillar (denoted as p-Si/ZnO nano-emitter). The anode voltage not only extracted the electron emission from the emitter apex but also induced the inter-band electron tunneling at the surface of the p-Si/ZnO nano-junction. The designed p-Si/ZnO emitter is equivalent to a ZnO nano-tip individually ballasted by a p-Si/ZnO diode and a parasitic tunneling field effect transistor (TFET) at the surface of the p-Si/ZnO junction. The parasitic TFET provides a channel for the supply of emitting electron, while the p-Si/ZnO diode is benefit for impeding the current overloading and prevent the emitters from a catastrophic breakdown. Well repeatable and stable field emission current were obtained from the p-Si/ZnO nano-emitters. High performance nano-emitters was developed using diamond-like-carbon coated p-Si/ZnO tip array (500 × 500), i.e., 178 μA (4.48 mA/cm2) at 75.7 MV/m.

Molten thermoplastic dripping behavior induced by flame spread over wire insulation under overload currents

The dripping behavior of the molten thermoplastic insulation of copper wire, induced by flame spread under overload currents, was investigated for a better understanding of energized electrical wire fires. Three types of sample wire, with the same polyethylene insulation thickness and different core diameters, were used in this study. First, overload current effects on the transient one-dimensional wire temperature profile were predicted using simplified theoretical analysis; the heating process and equilibrium temperature were obtained. Second, experiments on the melting characteristics were conducted in a laboratory environment, including drop formation and frequency, falling speed, and combustion on the steel base. Third, a relationship between molten mass loss and volume variation was proposed to evaluate the dripping time and frequency. A strong current was a prerequisite for the wire dripping behavior and the averaged dripping frequency was found to be proportional to the square of the current based on the theoretical and experimental results. Finally, the influence of dripping behavior on the flame propagation along the energized electrical wire was discussed. The flame width, bright flame height and flame spreading velocity presented different behaviors.

Study on Metallographic Structure of Melted Breakpoint mark for Copper Wire Current Overloading

As a common electrical fault causing fire, current overload results in some trace evidences on the wire. However, most of relative evidences, such as insulating layer, metal core, are likely to be destroyed or disturbed by fire. The majority of wire evidences from fire are asked to test melted breakpoints marks of the wire. Thus, it is significant to clearly reveal the metallographic features of melted breakpoint mark for wire overloading for fire investigators. This paper selected two kinds, single-core and multi-cores, 1.5mm2 copper wires to make melted breakpoints with 100A current overload. Then, this paper did some research on the fire heat influence on the microstructure of melted breakpoints. Experimental results indicated that the metallographic structure of the melted breakpoint mark caused by current overload was significantly different from that of melted mark caused by fire and short circuited melted mark. As for melted breakpoint marks of copper wire overloading, the most distinctive feature of the metallographic structure was dendritic segregations existing.

Offloading Cellular Traffic Through Opportunistic Communications: Analysis and Optimization

Offloading traffic through opportunistic communications has been recently proposed as a way to relieve the current overload of cellular networks. Opportunistic communication can occur when mobile device users are (temporarily) in each other's proximity, such that the devices can establish a local peer-to-peer connection (e.g., via WLAN or Bluetooth). Since opportunistic communication is based on the spontaneous mobility of the participants, it is inherently unreliable. This poses a serious challenge to the design of any cellular offloading solutions, that must meet the applications' requirements. In this paper, we address this challenge from an optimization analysis perspective, in contrast to the existing heuristic solutions. We first model the dissemination of content (injected through the cellular interface) in an opportunistic network with heterogeneous node mobility. Then, based on this model, we derive the optimal content injection strategy, which minimizes the load of the cellular network while meeting the applications' constraints. Finally, we propose an adaptive algorithm based on control theory that implements this optimal strategy without requiring any data on the mobility patterns or the mobile nodes' contact rates. The proposed approach is extensively evaluated with both a heterogeneous mobility model as well as real-world contact traces, showing that it substantially outperforms previous approaches proposed in the literature.

Self-Oscillating Fluxgate-Based Quasi-Digital Sensor for DC High-Current Measurement

A quasi-digital dc current sensor with rated current of ±600 A while overload current of about ±750 A is proposed in this paper. The new sensor is based on the open-loop self-oscillating fluxgate technology, but its originality is using a microcontroller unit to detect the duty cycle of the exciting voltage of the fluxgate. Compared with the published similar method, the whole signal chain of the new sensor is quasi-digital and without low-pass filter and analog-to-digital converter required when connected to digital systems. A precisely theoretical equation with respect to the linear dependence between the duty cycle and the current to be measured is established. Based on the equation, factors affecting the sensor sensitivity, accuracy, and resolution are determined, which constitutes the theoretical basis on the optimization design of the new sensor. The sensor linearity is improved using the least-squares polynomial fitting method. Some key specifications including the linearity, repeatability, and power supply effect of the sensor are characterized. The measurement results show that the linearity of the new sensor with the theoretical equation is better than 1.7% in the full scale of ±600 A, and can be improved to 0.3% when the fifth-order polynomial fitting method is used.

General linearized model use for High Power Reliability Assessment test results: Conditions, procedure and case study

In semiconductor manufacturing for automotive, AECQ_100 standard requires test of load drivers in continuous short circuit conditions: this test is called High Power Reliability Assessment (HPRA). It is about a robustness test in which a sample of parts is led to breakages on a cycled overload or short circuit current. The test is stopped when a sufficient number of parts to conduct a statistical analysis failed. The expected result from this statistical analysis is failure cycle modeling according to the test temperature. But this is a complex modeling that has to proceed in several steps, the final step being use of a general linearized model.This paper presents the main features of modeling, but it shows their implementation on a real HPRA test in Load Short Circuit (LSC) condition. Modeling allows result prediction at a temperature for which a test has not been performed, but it allows also a full explanation of the phenomena: for example, it enables to estimate activation energy of acceleration factor in the test, but also the failure mechanisms at the breakage origin. This paper highlights the necessary conditions for the tests so that interpretation may be complete and significant.

A research analytics framework‐supported recommendation approach for supervisor selection

AbstractIdentifying a suitable supervisor for a new research student is vitally important for his or her academic career. Current information overload and information disorientation have posed significant challenges for new students. Existing research for supervisor identification focuses on quality assessment of candidates, but ignores indirect relevance with candidate supervisors' previous students, social network connections and their thinking styles. This paper presents a comprehensive student‐centric approach based on research analytics framework for finding and recommending supervisors for new students. In particular, it integrates multiple measurements from three dimensions, ie, relevance, connectivity and quality. A prototype system was developed to support student–supervisor recommendations on a research social network platform (ie, www.ScholarMate.com). The results of user‐based evaluations demonstrate that our proposed approach generates more satisfactory recommendations as compared with that of all baseline methods.

Control System for the Mountainous Orchard Electric-Drive Monorail Transporter

In order to reduce operation risk and working intensity in mountainous orchard transportation and to realize optimized control for the mountainous orchard electric-drive monorail transportation system, a mountainous orchard electric-drive monorail transporter control system was designed and developed in this study. The system mainly consists of modules as: manual and remote control, positioning, obstacle avoidance, speed measurement, motor control, electric-magnetic break, and the position limit. The driving speed, current consumption, break control, and battery pack running ability experiments were conducted to test the control system. Results indicated that, the transporter’s driving speed is 0.60~0.58 m/s when it is running on the ground with the load weight from 0 to 100kg. This speed is little affected by the load weight. The transporter’s driving speed is 0.45~0.28 m/s when it is climbing a steep hill with an angle of 39°. That speed is critically affected by the load weight. In further improvements, a shift mechanism will be introduced so that adjustable gear ratio could be achieved thus solve the current overload problem in a full load situation.

Heat Transfer Simulation to Liquid Nitrogen from HTS Tapes at the Overload Currents

Knowledge of HTS materials behavior at overload currents is important to design fault current limiters or fault protection systems of electro-technical devices. There are sharp voltage peaks and voltage oscillations during rectangular current pulses (DC current) on HTS tapes cooled by liquid nitrogen. It is common knowledge that a homogeneous liquid can withstand certain amount of overheating before switching to the boiling phase. In the liquid nitrogen during the increase of the heat flux there is superheating (temperature overshoot) and boiling hysteresis takes place. We explain voltage peaks and voltage oscillations by the hysteresis phenomenon in boiling nitrogen during the increase and decrease of the heat flux in the nitrogen which is a result of current redistribution in the HTS tapes. Based on the measurements of voltage and temperature of the HTS tapes during current overload and numerical analysis of the process we estimated the heat-transfer characteristics from the HTS tapes to liquid nitrogen. We also obtained the information about limiting superheating of the liquid nitrogen. The influence of covers of the HTS tapes on superheating of the nitrogen is also discussed.

On the probability of current and temperature overloading in power grids

The advent of renewable energy sources has huge implications for the design and control of power grids. On the engineering side, reliability is currently ensured by strict con- straints on current, voltage and temperature. However, with growing supply-side uncertainty induced by renewables, these will need to be replaced by probabilistic guarantees, allowing constraints on a given line to be violated with a low probability, e.g., several minutes per year. In the present note we illustrate, using large deviations techniques, how replacing (probabilistic) current constraints by temperature constraints can lead to capacity gains in power grids.

Structural analysis of SiC Schottky diodes failure mechanism under current overload

1.2 kV–10 A tungsten Schottky diodes (W-SBD) have been aged and tested at limit under current overload (surge current pulses) to determine their structural weakest spots. All devices showed no ageing at 40 A amplitudes and a surge current capability higher than 60 A. Infrared lock-in measurements have located the weakest spots on the surface of failed chips and allowed us to non-invasively infer their origin: Schottky barrier modification by metal contact change. After, a focused ion beam coupled with scanning electron microscope has been used to analyse the physical signature at these locations. These inspections have revealed that the destruction mechanism responsible for their failure was the electromigration and thermomigration of tungsten into aluminum, locally modifying the electrical behaviour of the Schottky barrier (loss of blocking capability).

Probe-based end-to-end overload control for networks of SIP servers

The Session Initiation Protocol (SIP) has been adopted by the IETF as the control protocol for creating, modifying and terminating multimedia sessions. Overload occurs in SIP networks when SIP servers have insufficient resources to handle received messages. Under overload, SIP networks may suffer from congestion collapse due to current ineffective SIP overload control mechanisms. This paper introduces a probe-based end-to-end overload control (PEOC) mechanism, which is deployed at the edge servers of SIP networks and is easy to implement. By probing the SIP network with SIP messages, PEOC estimates the network load and controls the traffic admitted to the network according to the estimated load. Theoretic analysis and extensive simulations verify that PEOC can keep high throughput for SIP networks even when the offered load exceeds the capacity of the network. Besides, it can respond quickly to the sudden variations of the offered load and achieve good fairness.

Development of a CSR model for practice: connecting five inherent areas of sustainable business

Abstract The current overload of sustainability standards as well as the oversimplification of traditional management systems are two factors which often prevent organizations from translating their sustainable aspirations into their core strategy. In this context and in view of a strategic and profound embedding of the CSR-concept, this study proposes a conceptual CSR framework, mainly on the basis of the recently published umbrella guideline ISO 26000. The proposed model for practice goes beyond the limitations of traditional PDCA cycles, through applying interconnected soft and hard factors as building blocks within a circular framework, thereby aiming to reduce the gap between the execution of loose sustainable initiatives and the application of a sustainability balanced scorecard. The framework has been named ‘Sus5’, as it connects five inherent features of sustainable business (management knowledge & commitment, stakeholder knowledge & commitment, strategic planning, knowledge & commitment on the work floor, and operational execution & monitoring). The added empirical study, which has been executed within the Flemish business landscape, reflects on the average Flemish as-is attention for each independent proposed building block, thereby aiming to retrieve in which extent the attention areas of the average company are aligned with the ones of Sus5 as the basis for drawing conclusions on the general feasibility level of applying Sus5. Through its intuitive and pragmatic character, Sus5 might in this context firstly serve as a practical tool for organizations to undertake a self-assessment and detect possible gaps in their CSR-policy, secondly to motivate them to shift the emphasis to a broader set of attention areas, based on the realization that a thorough CSR policy consists of a set of interdependent building blocks, being bonded by causal relations.