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Electromagnetic Wave Theory for Calculation of Exact Magnetic Field in Case of BWO
摘要： Overall efficiency of high power microwave generating device depends upon input current in the form of electron beam and currents required for electromagnets. In order to increase the efficiency of device, if electromagnets are replaced by permanent magnets, overall efficiency of device shall increase. So, calculation of exact magnetic field is required. In this paper, the exact relation of magnetic field required in high power microwave generation using Backward Wave Oscillator (BWO) is found. BWO interacts with slow waves and is the most promising device to produce high power microwaves. The interaction involves the beams from high current density and the waveguide mode. An exact relation that specifically relates the various parameters of the waveguide like slow wave structures (SWS) dimensions, input beam voltage and operational frequency with axial magnetic field is derived. The derived equation gives calculation of exact values of magnetic field for focusing of beams. Theoretical and simulated work show good agreement with the previously available experimental data. So, with the derived electromagnetic wave relation exact value of magnetic field is calculated for desired frequency and power regime.
关键词： High current electron,High power microwave,Wiggler,Magnetic field,Oscillator
更新于2025-09-04 15:30:14
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Intelligent PV Power System with Unbalanced Current Compensation Using CFNN-AMF
摘要： A novel method is proposed to compensate the three-phase unbalanced currents of power grid under three-phase unbalanced load for a two-stage photovoltaic (PV) power system without the augmentation of active power filter (APF). The PV power system is composed of an interleaved DC/DC converter and a three-level neutral-point clamped (NPC) inverter. Moreover, the PV power system possesses the smart inverter function, in which the output active and reactive powers of the PV inverter are predetermined by a power factor according to grid codes of the utilities. In the proposed method, the dq0-axis compensation currents are obtained through low pass filters (LPFs) to compensate the three-phase unbalanced currents of power grid. Furthermore, in order to improve the control performance of the DC bus voltage of the PV power system under unbalanced load variation condition, an online trained compensatory neural fuzzy network with an asymmetric membership function (CFNN-AMF) is proposed to replace the traditional proportional-integral (PI) controller for the DC bus voltage control. In the proposed CFNN-AMF, the compensatory parameter to integrate pessimistic and optimistic operations of fuzzy systems is embedded in the CFNN. In addition, the dimensions of the Gaussian membership functions are directly extended to AMFs. Additionally, the proposed controllers of the PV power system are implemented by two control platforms using floating-point digital signal processor (DSP). Finally, excellent compensation performance for the three-phase currents of power grid under three-phase unbalanced load can be achieved from the experimental results.
关键词： asymmetric membership function,PV power system,compensatory neural fuzzy network,unbalanced current compensation,three-level neutral-point clamped inverter,interleaved DC/DC converter
更新于2025-09-04 15:30:14
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Solar powered oxygen systems in remote health centers in Papua New Guinea: a large scale implementation effectiveness trial
摘要： Background Pneumonia is the largest cause of child deaths in Papua New Guinea (PNG), and hypoxaemia is the major complication causing death in childhood pneumonia, and hypoxaemia is a major factor in deaths from many other common conditions, including bronchiolitis, asthma, sepsis, malaria, trauma, perinatal problems, and obstetric emergencies. A reliable source of oxygen therapy can reduce mortality from pneumonia by up to 35%. However, in low and middle income countries throughout the world, improved oxygen systems have not been implemented at large scale in remote, difficult to access health care settings, and oxygen is often unavailable at smaller rural hospitals or district health centers which serve as the first point of referral for childhood illnesses. These hospitals are hampered by lack of reliable power, staff training and other basic services. Methods We report the methodology of a large implementation effectiveness trial involving sustainable and renewable oxygen and power systems in 36 health facilities in remote rural areas of PNG. The methodology is a before–and after evaluation involving continuous quality improvement, and a health systems approach. We describe this model of implementation as the considerations and steps involved have wider implications in health systems in other countries. Results The implementation steps include: defining the criteria for where such an intervention is appropriate, assessment of power supplies and power requirements, the optimal design of a solar power system, specifications for oxygen concentrators and other oxygen equipment that will function in remote environments, installation logistics in remote settings, the role of oxygen analyzers in monitoring oxygen concentrator performance, the engineering capacity required to sustain a program at scale, clinical guidelines and training on oxygen equipment and the treatment of children with severe respiratory infection and other critical illnesses, program costs, and measurement of processes and outcomes to support continuous quality improvement. Conclusions This study will evaluate the feasibility and sustainability issues in improving oxygen systems and providing reliable power on a large scale in remote rural settings in PNG, and the impact of this on child mortality from pneumonia over 3 years post–intervention. Taking a continuous quality improvement approach can be transformational for remote health services.
关键词： Pneumonia,Papua New Guinea,oxygen therapy,hypoxaemia,solar power,remote health centers
更新于2025-09-04 15:30:14
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[IEEE 2018 IEEE 6th Workshop on Wide Bandgap Power Devices and Applications (WiPDA) - Atlanta, GA, USA (2018.10.31-2018.11.2)] 2018 IEEE 6th Workshop on Wide Bandgap Power Devices and Applications (WiPDA) - Evaluation of GaN Based Multilevel Converters
摘要： With the significant reduction in board space occupied by the smaller GaN transistors, topologies that require a greater number of active devices as a tradeoff for reduced passive size, the main barrier to higher density, have become attractive. Switched capacitor multilevel converters are good examples of topologies that can effectively reduce or eliminate passive components. Two GaN based proof-of-concept designs (three-level converters), one for a low voltage (LV) 48 V server application and the other for a higher voltage (HV) 400 V power factor correction (PFC) circuit are discussed in this paper. As a result of using lower figure-of-merit (FOM) devices, significant efficiency gains are observed for the LV and HV converters developed in this paper compared to a two-level topology. Smaller passive size (mainly inductors) also provides a significant increase in power density for the LV converter. A startup scheme is discussed which eliminates the need for extraneous control loops or high voltage rated devices for the top switch. Finally, an electrical performance comparison is also shown for a two-stage intermediate bus architecture (IBA) developed with the GaN based three-level converter for the front end and a high frequency GaN-based second buck stage for 48 V to 1 V point-of-load (PoL) conversion. Two choices of intermediate bus voltage are investigated: 12 V and 6 V. Each bus voltage demonstrates its advantage in a certain range of load current.
关键词： efficiency,DC-DC converter,GaN,Startup,power density,IBC,Multilevel
更新于2025-09-04 15:30:14
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[IEEE 2018 IEEE 6th Workshop on Wide Bandgap Power Devices and Applications (WiPDA) - Atlanta, GA, USA (2018.10.31-2018.11.2)] 2018 IEEE 6th Workshop on Wide Bandgap Power Devices and Applications (WiPDA) - High Voltage GaN Switch Reliability FIT rates and PPM reliability based on standards from: Joint Electron Device Engineering Council (JEDEC), Automotive Electronics Council (AEC) and German Electrical and Electronic Manufacturers' Association (ZVEI)
摘要： Adoption of any semiconductor technology by the power conversion market requires the understanding of fundamental failure modes, acceleration factors and reliability statistics. This study shows how GaN products from Transphorm can meet this challenge, especially in the critical High Voltage Off State (HVOS) reliability stress test. The anticipated failure rate during a product’s first 10 to 20 years of use is of particular interest as it has direct impact on warranty costs. This market requirement can be addressed by testing to failure statistically significant samples of devices, and analyzing the data with appropriate models. The methods developed for measuring GaN reliability on large samples will be discussed, which are wholly based on existing industrial and automotive standards. The resulting data can be used to supplement qualification testing results when the failure modes and acceleration factors are well understood.
关键词： GaN,FIT,PPM,HEMT,acceleration factor,power electronics,reliability
更新于2025-09-04 15:30:14
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[IEEE 2018 IEEE 6th Workshop on Wide Bandgap Power Devices and Applications (WiPDA) - Atlanta, GA, USA (2018.10.31-2018.11.2)] 2018 IEEE 6th Workshop on Wide Bandgap Power Devices and Applications (WiPDA) - Thermal and Thermomechanical Modeling to Design a Gallium Oxide Power Electronics Package
摘要： There is significant interest in the power electronics industry in transitioning from silicon to wide-bandgap devices. Gallium oxide devices have the potential to offer comparable or even superior performance than other wide-bandgap devices, but at a much lower cost. Recent breakthroughs include demonstration of a laboratory-scale gallium oxide transistors and diodes; however, a functional power electronics package for these devices is yet to be developed. In this paper, the research methodology in designing an electronics package for gallium oxide devices is outlined. Finite element-based thermal and thermomechanical modeling simulations were conducted to realize a package design that meets the combined target of minimal thermal resistance and improved reliability. Different package designs that include various material combinations and cooling configurations were explored, and their thermal and thermomechanical performance are reported. Furthermore, the short-circuit withstanding capabilities of gallium oxide devices were studied and compared with silicon carbide.
关键词： gallium oxide,thermal modeling,thermomechanical modeling,finite-element,high-temperature packaging,power electronics,wide-bandgap devices
更新于2025-09-04 15:30:14
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[IEEE 2018 IEEE International Workshop on Electromagnetics: Applications and Student Innovation Competition (iWEM) - Nagoya, Japan (2018.8.29-2018.8.31)] 2018 IEEE International Workshop on Electromagnetics:Applications and Student Innovation Competition (iWEM) - A Hybrid MoM/FDTD Method for Exposure Assessment of Wireless Power Transfer Systems
摘要： A hybrid method combining method of moments (MoM) and finite-difference time-domain (FDTD) method is proposed to evaluate exposure in a human body close to wireless power transfer (WPT) systems. Validation of the proposed method has been demonstrated by analysis of a WPT system close to a dielectric cube. Finally, the proposed method was used to determine specific absorption rate inside a human body in the vicinity of a spiral-type WPT system.
关键词： hybrid method,method of moments,exposure assessment,FDTD,wireless power transfer
更新于2025-09-04 15:30:14
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Normalized power propagation on 1x6 fiber coupler
摘要： The simulation of normalized power propagation on interaction region of 1x6 monolithic fiber coupler is reported. Power distribution on fiber couplers is much affected by arrangement of fibers. The theoretical model has been used to calculate power coupling propagation on linear and pentagonal arrangement of 1x6 fiber coupler. The calculation is based on a matrix transfer which is the solution of coupled-mode theory. The six parallel fiber is in linear array and pentagonal placement. By launching input power to single input of 1x6 monolithic fiber couplers for both configurations, power distribution shows how the initial power is distributed to the others. It is found that linear configuration cannot initiate its power to the initial fiber, and maximum peak is not periodically such as power propagation on 1x2 and 1x3 fiber coupler. By changing the arrangement to be a pentagonal and one fiber as in the center where input power is launched, the input power will be distributed identically from the center to five surrounding fibers. At certain coupling length, about 4.7 mm and 6.3 mm, six fibers with pentagonal configuration will have identical output power for wavelength input 1550 and 1310 nm respectively. Based on this distribution, 1x6 monolithic fiber couplers are applicable as a power divider.
关键词： linear and pentagonal configurations,1x6 monolithic fiber couplers,power propagation
更新于2025-09-04 15:30:14