Analysis of a three-coil contactless power transfer system for high-power applications

Recently, contactless power transfer (CPT) has become very popular in various fields of applications such as electronic appliances, medical implant devices, electrical vehicles, etc. When air gap distance between the transmitting and receiving coils of a CPT system increases, coupling coefficient between the coils decreases. In a large-air-gap CPT system, by incorporating an additional coil between the transmitting and receiving coils, coupling coefficient can be enhanced. Consequently, efficiency of a large-air-gap CPT system is improved. In this study, a three-coil system has been compared with a two-coil system using basic circuit models. Thereafter, the basic circuit models of two-coil and three-coil systems have been studied to confirm energy efficiency differences between the two systems for high-power applications. Using simplified circuit models, conditions for higher energy efficiency of a three-coil system than a two-coil system have been derived and it has been established that power transfer efficiency of a three-coil system has improved significantly in comparison with a traditional two-coil system. To confirm the theory, a two-coil and a three-coil systems with an air gap distance of 18 cm and a lateral misalignment of 3.5 cm have been verified using Ansys simulation tool for an output power of 2 kW.     

Fuel cell power conditioning for electric power applications: a summary

Fuel cells are considered to be one of the most promising sources of distributed energy because of their high efficiency, low environmental impact and scalability. Unfortunately, multiple complications exist in fuel cell operation. Fuel cells cannot accept current in the reverse direction, do not perform well with ripple current, have a low output voltage that varies with age and current, respond sluggishly to step changes in load and are limited in overload capabilities. For these reasons, power converters are often necessary to boost and regulate the voltage as a means to provide a stiff applicable DC power source. Furthermore, the addition of an inverter allows for the conversion of DC power to AC for an utility interface or for the application of an AC motor. To help motivate the use of power conditioning for the fuel cell, a brief introduction of the different types, applications and typical electrical characteristics of fuel cells is presented. This is followed by an examination of the various topologies of DC-DC boost converters and inverters used for power conditioning of fuel cells. Several architectures to aggregate multiple fuel cells for high-voltage/high-power applications are also reviewed.     

Coil geometry models for power loss analysis and hybrid inductive link for wireless power transfer applications

This paper presents a hybrid inductive link for Wireless Power Transfer (WPT) applications. Achieving better power transfer efficiency over a relatively wider distance across coils is the prime objective in most of the WPT systems, but often suffers from power loss in the near field area of inductively coupled coils. One of the reasons for this power loss is the pattern of the magnetic field produced by the source coil used in the WPT system. Mostly the nature of magnetic field produced by the source coil is distributed radially over the coil, in which the produced magnetic field is not fully utilized. Achieving better efficiency and load current by reducing power loss is the main driving force of this work. One of the viable methods to reduce the power loss is by increasing the field intensity thereby redirecting the flux lines flow to be directional. With this aim, three coils such as solenoid, spiral and conical are designed and simulated to determine the magnetic field strength using Finite Element Method. The conical coil produces the highest self-inductance of 8.63 µH and a field strength of 1.542 Wb with the coil thickness of 3.20 mm. Then, WPT system is demonstrated with the inclusion of Maximum Power Point Tracking algorithm for improving efficiency. The schematic of flux generation of both in the transmitter and receiver sections are demonstrated and analyzed graphically. The efficiency of both simulation and experimental measurements are matched well with similar progression. The effect of parameters (angle, distance, and load resistance) on the efficiency is explored. The outcomes conclude that the inductive coupling has achieved 73% (average case) power transfer wirelessly over a distance of 5 cm with an input voltage of 5 V and 5 MHz frequency.     

Dielectric mirrors for high power laser applications

Development of low loss dielectric high reflecting mirrors for high power laser applications presents some problems in selecting suitable thin film materials and in understanding their optical constants. Some of these problems have been solved by a systematic study of the dependence of optical constants on different evaporation parameters for a number of thin film materials. Using the data thus obtained high reflecting dielectric mirrors for different laser applications in theuv, visible and near-infrared regions were successfully developed indigenously by the method of vacuum evaporation.     

All-optical 100-Gbit/s word packet time-division-multiplexed access node in a looped-back configuration: enabling technologies for sequential add-drop functionality

We experimentally demonstrate the adding, dropping, and passing through of 100-Gbit/s word packets in a looped-back all-optical time-division-multiplexed (TDM) access node. Packets are routed with a 17-dB contrast ratio and demultiplexed with a 20-dB contrast ratio. This node uses short 100-Gbit/s words to demonstrate its potential to process data packets from multiple sources and to perform packet switching in a multinode ring network configuration. The ability to tolerate timing jitter as well as varying input signal characteristics is essential to an all-optical access node in a multinode network. For 2-ps input pulses, the header processor has a timing window of ~5 ps, and the demultiplexer has a timing window of ~5.5 ps. This allows for tolerance to bit-to-bit timing jitters or to an increase in the pulse width of as much as 3 ps. Packet-to-packet timing jitter is detected and compensated by the technique used to synchronize the local source to each packet. The key enabling technologies of an all-optical TDM packet add-drop multiplexer are discussed, including an erbium-doped fiber laser, a nonlinear optical loop mirror logic gate, self-synchronization to incoming packets with a fast-saturation/slow-recovery gain element followed by an intensity discriminator, a two-wavelength nonlinear optical loop mirror demultiplexer, and synchronization of new packets to the network packet rate with a phase-locked loop. The local source is automatically synchronized to the incoming packet, because it uses an extracted pulse from the packet, which has a contrast ratio of >20 dB to the rest of the packet. Finally, new packets are added by use of a local laser and a synchronization method, which gives a timing jitter of ~1 ps. Using a statistical method of measuring Q value with picosecond resolution, we show that a header processor with two cascaded logic gates has a Q value of 7.1 with a 95% confidence level.     

The rotating bed reactor as a power source for EM gun applications

Electromagnetic gun applications of the Rotating Bed Reactor (RBR) are examined. The RBR is a compact (∼ 1 m³), (up to several thousand MW(th)), high-power reactor concept, capable of producing a high-temperature (up tosim 3000degK) gas stream with a MHD generator coupled to it, the RBR can generate electric power (up to ∼ 1000 MW(e)) in the pulsed or cw modes. Three EM gun applications are investigated: a rail gun thruster for orbit transfer, a rapid-fire EM gun for point defense, and a direct ground-to-space launch. The RBR appears suitable for all applications.     

An overview of protective action decision-making for a nuclear power plant emergency

Protection of the public in a nuclear power plant emergency requires decision-makers to balance the time requirements from two chains of events: the events associated with a radiological release and the events involved with the response to that release. The management of these events is distributed among personnel at the nuclear plant, in the local community, and in state and federal agencies. All of these parties must coordinate their response to the emergency to assure that timely and effective protective response can be made by the risk area population. This article describes the process by which protective action recommendations (PARs) are developed in nuclear power plant emergency exercises and provides recommendations from research on emergency response in other types of natural and technological hazards.     

Triboelectricity-assisted transfer of graphene for flexible optoelectronic applications

In this work, we developed a novel triboelectricity-assisted polymer-free method for the transfer of large-area chemical vapor deposited graphene films. With the assistance of electrostatic forces from friction-generated charges, graphene sheets were successfully transferred from copper foils to flexible polymer substrates. Characterization results confirmed the presence of high quality graphene with less defects and contaminations, compared to graphene transferred by conventional poly(methyl methacrylate)-mediated processes. In addition, the graphene samples possessed outstanding electrical transport capabilities and mechanical stability, when studied as electron transfer matrixes in graphene/ZnO hybrid flexible photodetectors. Our results showed a broad application potential for this transfer method in future flexible electronics and optoelectronics.

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Compact piezoelectric stacked actuators for high power applications

Small, hollow, multilayer actuators with a diameter of 3 mm were fabricated by the stacking method from piezoelectric hard lead zirconate titanate (PZT) ceramics. Langevin vibrators were also constructed with the hollow multilayer actuators. The performance capabilities of the actuator and Langevin vibrator samples were examined under high-power conditions. The high-power vibration level at a given sinusoidal drive voltage was significantly enhanced by using a multilayer structure under either a nonresonance or resonance condition. A maximum vibration velocity of 0.17 m/sec was obtained for the 9-layer actuator sample under nonresonance conditions. The vibration velocity was further improved with the Langevin vibrator driven at the resonance frequency. The temperature rise due to heat generation under high-power conditions was the immediate limitation on the maximum accessible vibration velocity for the stacked actuators.     

Nanofluids for power engineering: Emergency cooling of overheated heat transfer surfaces

The possibility of emergency cooling of an overheated heat transfer surface using nanofluids in the case of a boiling crisis is explored by means of synchronous recording of changes of main heat transfer parameters of boiling water over time. Two nanofluids are tested, which are derived from a mixture of natural aluminosilicates (AlSi-7) and titanium dioxide (NF-8). It is found that the introduction of a small portions of nanofluid into a boiling coolant (distilled water) in a state of film boiling (t _heater > 500°C) can dramatically decrease the heat transfer surface temperature to 130–150°C, which corresponds to a transition to a safe nucleate boiling regime without affecting the specific heat flux. The fact that this regime is kept for a long time at a specific heat load exceeding the critical heat flux for water and t _heater = 125–130°C is particularly important. This makes it possible to prevent a potential accident emergency (heater burnout and failure of the heat exchanger) and to ensure the smooth operation of the equipment.     

Investigation of natural convection heat transfer performance of the QFN-PCB electronic module by using nanofluid for power electronics cooling applications

Natural convection heat transfer of Cu-water nanofluid in a 3?×?3 array of a typical isothermal quad flat non-lead (QFN) embedded printed circuit board (PCB) module which can be bounded with respect to the sealed non-Darcy porous enclosure is numerically investigated. The Darcy-Brinkman-Forchheimer model is adopted to model the fluid flow in the porous medium under the presence of an external magnetic field. The transport governing equations are solved by the finite volume method based on the SIMPLE algorithm and the power law scheme. Main efforts focus on the effects of the parameters such as a nanoparticle volume fraction, Hartmann number, Darcy number and the enclosure side aspect ratio on the fluid flow and heat transfer characteristics inside the enclosure. The obtained results indicate that the influence of nanofluid of the overall Nusselt number increases with increasing the Darcy number, but decreases with increasing the Hartmann number. The overall Nusselt number attains its maximum value in the range of enclosure side aspect ratio from 1.5 to 3 with respect to the Darcy number. Moreover, the proposed correlations improve the efficiency, reliability and stability of the electronic device encountered in various applications in electronic industries.     

Radiative transfer code SHARM for atmospheric and terrestrial applications

An overview of the publicly available radiative transfer Spherical Harmonics code (SHARM) is presented. SHARM is a rigorous code, as accurate as the Discrete Ordinate Radiative Transfer (DISORT) code, yet faster. It performs simultaneous calculations for different solar zenith angles, view zenith angles, and view azimuths and allows the user to make multiwavelength calculations in one run. The Delta-M method is implemented for calculations with highly anisotropic phase functions. Rayleigh scattering is automatically included as a function of wavelength, surface elevation, and the selected vertical profile of one of the standard atmospheric models. The current version of the SHARM code does not explicitly include atmospheric gaseous absorption, which should be provided by the user. The SHARM code has several built-in models of the bidirectional reflectance of land and wind-ruffled water surfaces that are most widely used in research and satellite data processing. A modification of the SHARM code with the built-in Mie algorithm designed for calculations with spherical aerosols is also described.     

Open-cell porous metals for thermal management applications: fluid flow and heat transfer

Porous metals are produced by a wide range of industrially applied techniques, and the resulting porous structure is a characteristic of the manufacturing method chosen. This review firstly provides an overview of the different techniques to manufacture open-cell porous metals, highlighting the distinction between the resulting porous structures. The effects of the structural parameters on the fluid flow properties and heat transfer in porous metals are also discussed. It was evident from literature that there exist optimum structural parameters which offered maximum thermal exchange performance. Therefore, the last part of this review outlines the current research on porous metals for thermal management applications, which focuses on optimising the design of the porous metal structure to improve the heat transfer performance.

This review was submitted as part of the 2016 Materials Literature Review Prize of the Institute of Materials, Minerals and Mining run by the Editorial Board of MST. Sponsorship of the prize by TWI Ltd is gratefully acknowledged     

A new universal gate for low power SoC applications

This paper formulates a new design technique for an area and energy efficient Universal NAND gate. The proposed robust three transistors (3T) based NAND gate is just as effective for dynamic power control in CMOS VLSI circuits for System on Chip (SoC) applications. The 3T NAND gate is intuitively momentous and lead to better performance measures in terms of dynamic power, reduced area and high speed while maintaining comparable performance than the other available NAND gate logic structures. Simulation tests were performed by employing standard Berkeley Predictive Technology Model (BPTM) 22 nm, 45 nm and 90 nm process technologies. The experiment and simulation results show that, the proposed 3T NAND gate effectively outperforms the basic CMOS NAND gate with excellent driving capability and signal integrity with exact output logic levels.     

Recent advances in creep-resistant steels for power plant applications

The higher steam temperatures and pressures required to achieve increase in thermal efficiency of fossil fuel-fired power-generation plants necessitate the use of steels with improved creep rupture strength. The 9% chromium steels developed during the last three decades are of great interest in such applications. In this report, the development of steels P91, P92 and E911 is described. It is shown that the martensitic transformation in these three steels produces high dislocation density that confers significant transient hardening. However, the dislocation density decreases during exposure at service temperatures due to recovery effects and for long-term creep strength the sub-grain structure produced under different conditions is most important. The changes in the microstructure mean that great care is needed in the extrapolation of experimental data to obtain design values. Only data from tests with rupture times above 3,000 h provide reasonable extrapolated values. It is further shown that for the 9% chromium steels, oxidation resistance in steam is not sufficiently high for their use as thin-walled components at temperatures of 600°C and above. The potential for the development of steels of higher chromium contents (above 11%) to give an improvement in steam oxidation resistance whilst maintaining creep resistance to the 9% chromium steels is discussed.     

Analysis of perforated magnetic shields for electric power applications

The shielding performance of perforated magnetic shields for electric power applications is described. The shielding of an axisymmetric induction heating device is studied as a function of frequency, number of perforations and dimensions of the perforations. From the numerical point of view, the perforations cause the numerical model to be 3D. A numerical optimisation is carried out to find the optimal geometry with respect to the shielding factor and the volume of the shield. For the optimisation, two approaches are presented. The first approach is fast and easy-to-implement, but has limited accuracy. It uses a classical 2D axisymmetric model where the perforations are approximated by 'axisymmetric air gaps' resulting in a segmented shield. It is shown how to modify the 2D model to obtain results that are similar to the ones of a 3D model. The second approach is more accurate although quite fast, but more difficult to implement. It combines a 3D thinshell finite element model with the unmodified 2D model in a space mapping optimisation algorithm. The validation of both models is based on experimental work for an unperforated shield and for the optimised perforated shield.     

Reliability evaluation of the power supply of an electrical power net for safety-relevant applications

In this paper, we introduce a methodology for the dependability analysis of new automotive safety-relevant systems. With the introduction of safety-relevant electronic systems in cars, it is necessary to carry out a thorough dependability analysis of those systems to fully understand and quantify the failure mechanisms in order to improve the design. Several system level FMEAs are used to identify the different failure modes of the system and, a Markov model is constructed to quantify their probability of occurrence. A new power net architecture with application to new safety-relevant automotive systems, such as Steer-by-Wire or Brake-by-Wire, is used as a case study. For these safety-relevant loads, loss of electric power supply means loss of control of the vehicle. It is, therefore, necessary and critical to develop a highly dependable power net to ensure power to these loads under all circumstances.     

Thermal and neutron-physical features of the nuclear reactor for a power pulsation plant for space applications

We have explored the possibility of creating small-size reactors with a high power output with the provision of thermal stability and nuclear safety under standard operating conditions and in emergency situations. The neutron-physical features of such a reactor have been considered and variants of its designs preserving the main principles and approaches of nuclear rocket engine technology are presented.