Power density has become increasingly important for applications where weight and space are limited. Power density is a unique challenge requiring the latest transistor technology to push switching frequency to shrink passive filter size. Furthermore, while high efficiency is an important thermal handling strategy, it must be weighed against increases in component size. Google's Little Box Challenge shone light on these challenges in pushing the power density of a 2kW inverter. The rise in electric vehicle infrastructure and demand represents a unique application for power electronics: pushing the power handling capability and functionality of bi-directional, on-board electric vehicle chargers for faster charging while simultaneously shrinking them in size. New wide-bandgap (WBG) devices, combined with soft-switching, now allow inverters to shrink in size by pushing to higher switching frequencies while maintaining efficiency. Classic H-Bridge topologies have limited switching frequency due to hard switching. Soft switching allows inverters to operate at higher frequency while minimizing switching loss. Concurrently, interleaving can reduce current handling stress and conduction loss better than simply paralleling two transistors. A novel interleaved auxiliary resonant snubber for high-frequency soft-switching is introduced. The design of an auxiliary resonant snubber is discussed; this allows the main GaN MOSFETs to achieve zero voltage switching (ZVS). The auxiliary switches and SiC diodes achieve zero current switching (ZCS). This soft-switching strategy can be applied to any modulation scheme. Here, it is applied to an asymmetrical unipolar H-bridge with two high frequency legs interleaved. While soft-switching minimizes switching loss, conduction loss is simultaneously reduced for high-power applications by interleaving two high frequency legs. This topology is chosen for its conduction loss reduction and bi-directional capability. / Master of Science / Electric vehicles have become a unique application for power electronics where battery chargers must both handle higher power and shrink in size and weight. The latest transistor technology allows the designer to push switching frequency, shrinking the size of components and increasing the power density. In 2014, Google’s Little Box Challenge shone light on the design trade-offs of high power density design with new transistor technology for a 2kW inverter. New semi-conductor materials now allow transistors to switch at higher frequency with less loss. To take advantage of these features, a new switching method is developed. The main power transistors are brought to zero voltage before turn-on with auxiliary switches and resonant current. Interleaving is added for better efficiency and power handling. With further control, this method could prove attractive for new, high-density power electronic designs. Applications for this include bi-directional chargers for electric vehicles in the 6kW range

Due to many advantages, swash plate pumps are wide spread in hydraulic systems. The main advantages are the through drive capability, the adjustability and most of all, the high power density. Their application range is limited, historically, to 450bar including medium and higher volume sizes. In higher pressure range, constant pumps such as wobbling disks or radial piston pumps are normally used. This is because the higher stressed parts can be dimensioned much bigger. Pumps with lower power such as constant displacement gear pumps are generally used in low price applications. In order to enlarge the application range of swash plate pumps, their advantages have to be further improved and strengthened. This paper shows by example how the pressure of the basic series A4VSO was increased up to a nominal pressure of 630bar and the historical pressure mark of 450bar could be exceeded. This increase in pressure level enables for example steel treatment manufacturers to reduce their component sizes without the need of a pressure transducer. Furthermore the power density of the redesigned HA4VSO was increased by 36%, compared to the standard A4VSO, by significantly increasing the self-priming speed. On the other side of the application range, in lower power mobile applications such as small tractors, forklift and skid steer loader, there is an increasing demand for less exhaust emissions and better fuel economy. The energy saving potential by changing from a hydraulic system with constant hydraulic pumps to variable hydraulic pumps is already proven on high power applications. By developing the variable axial piston pump A1VO to the requirements of lower horse power application, it is now also possible to realize such savings in lower horse power applications. Furthermore efficiency of the pump itself can be improved. An example of this is shown by way of the new A4 series 33.

The modification of anode materials is important to enhance the power generation of MFCs (microbial fuel cells). A novel and cost-effective modified anode that is fabricated by dispersing manganese dioxide (MnO2) and HNTs (Halloysite nanotubes) on carbon cloth to improve the MFCs' power production was reported. The results show that the MnO2/HNT anodes acquire more bacteria and provide greater kinetic activity and power density compared to the unmodified anode. Among all modified anodes, 75 wt% MnO2/HNT exhibits the highest electrochemical performance. The maximum power density is 767.3 mWm(-2), which 21.6 higher than the unmodified anode (631 mW/m(2)). Besides, CE (Coulombic efficiency) was improved 20.7, indicating that more chemical energy transformed to electricity. XRD (X-Ray powder diffraction) and FTIR (Fourier transform infrared spectroscopy) are used to characterize the structure and functional groups of the anode. CV (cyclic voltammetry) scans and SEM (scanning electron microscope) images demonstrate that the measured power density is associated with the attachment of bacteria, the microorganism morphology differed between the modified and the original anode. These findings demonstrate that MnO2/FINT nanocomposites can alter the characteristics of carbon cloth anodes to effectively modify the anode for practical MFC applications. (C) 2016 Elsevier Ltd. All rights reserved.

This dissertation proposes a novel control technique for power density maximization of the brushless DC (BLDC) generator which is a nonsinusoidal power supply system. In a generator of given rating, the weight and size of the system affect the fuel consumption directly, therefore power density is one of the most important issues in a stand-alone generator. Conventional rectification methods cannot achieve the maximum power possible because of a distorted or unsuitable current waveform. The optimal current waveform for maximizing power density and minimizing machine size and weight in a nonsinusoidal power supply system has been proposed theoretically and verified by simulation and experimental work. Also, various attributes of practical interest are analyzed and simulated to investigate the impact on real systems.

Active galactic nuclei (AGN) are known to vary in brightness in all regions of the electromagnetic spectrum and over a wide range of timescales. Many methods have been utilized to transform this observed variability into meaningful information about the central engines of AGN. One such technique, adapted from time series analysis of galactic x-ray binary systems, has been used to detect a characteristic break timescale in the power density spectra of x-ray variability in Seyfert galaxies. This timescale, thought to be related to instabilities in the accretion disk, appears to scale with black hole mass over many orders of magnitude. This dissertation performs similar time series analyses with the optical data of eight blazars. The majority of these objects also display a characteristic break timescale. In cases where a black hole estimate is known, the timescales are in good agreement with the relationship observed for galactic x-ray binary systems and Seyfert galaxies. For objects of unknown mass, this relationship can be used to provide a mass estimate of the supermassive black hole. Comparisons are made between the structure function and power density spectrum for each object, and the implications for the connection between the accretion disk and the relativistic jet in AGN are discussed.

This work presents design and fabrication technologies on vibration-induced electromagnetic micro-generators using LTCC (Low temperature co-fire ceramic) processes. LTCC fabrication with some special advantages has simplistically processes and multilayer stack procedure, resulting in a micro-inducer can consist of the multilayer silver (Ag) induction micro-coils and a helical ceramic micro-spring. Highly electrical conductible Ag and its multilayer micro-coil structures can enhance the power output of generators. This work is composed of three parts. The first part describes the design of two kinds of micro-generator; a magnetic core generator (MCG) and sided-magnet generator (SMG). According to their respective structures, an analytical mode is also developed to investigate its resonant frequency and the spring constant of the micro-spring, as well as the bending stress and fatigue life of the supporting beam. The voltage output, current output and power output on the helical induction micro-coils, as well as the relationship of vibration amplitude versus vibration frequency in the vibrating system are calculated. The second part introduces how to integrate the Ag multilayer induction micro-coils and the helical ceramic micro-spring using LTCC technique, and organize the design and fabrication of LTCC micro-inducers. From the fabrication procedures, it is known that a stacking error places a limit on the total numbers of micro-coils layer. The experimental results verify that the application of LTCC to the fabrication of micro-inducers is feasible, and that the phenomenon of plane warpage, volumetric shrinkage, layer delamination and surface crack of sintered ceramic structures has been fully controlled. In the third part, measurement setup, vibrating tests and experiments on generating electricity are completed. The performances with different-structure devices are evaluated. Voltage output, current output and power output, as well as changing trends of power density with respect to the layer number of induction micro-coils and magnets are discussed. Relationship of the electrical parasitical damping coefficient versus the vibration amplitude and vibration velocity, relationship between the induced inductor and the current output, the power output depending on the electrical load resistance and differences between fabrication lots are investigated. At last, comparisons between analytical and experimental power output are conduced. For MCG micro-generator, the analytical value is 0.88 mW, about 13.6% smaller than the experimental value of 1 mW. For SMG micro-generator, the analytical value is 1.73 mW, about 10.7% larger than the measured value of 1.56 mW. The analytical models are verified. In the MCG device, the experimental results show that a maximum voltage output of 25.19 mV, a current output of 82.9 mA and a power density of 2.36 mW/cm3 under 120 Hz frequency and 0.03-mm amplitude are obtained. In addition, when operated at 69 Hz vibration frequency and vibration amplitude of 0.03 mm, the experimental maximum voltage output, current output and power density of the SMG device are 44.5 mV, 83.1 mA and 2.17 mW/cm3, respectively. Except the power density, other electricity performances of SMG device are better than MCG. Apparently, the power density of MCG and SMG device presented by this study competes favorably with the results from other devices in the literature.

Taiwan lack natural and energy resource, need to import 99.3% energy. Due to the traditional high-carbon energy also supply from abroad, its supply will be impacted by international demand and production, price fluctuations, and the international politics. In recent years the international oil price surged upward, business costs were constantly raise. In this study, some small and medium businesses are taken as objects in Kaohsiung, Taiwan. In this investigation, understand the application of energy resource in those businesses, different industries have their attention to other items and differences, it can be seen on those small and medium enterprises in the concept and practice by measuring and computing power consumption. Research Methods: First, to explore the international and domestic energy and policy and the related energy research literature, interview the small and medium enterprises and observe the way of energy usage, and provide the improving solution, questionnaires and field measurements made on those enterprises, to record the response, investment willingness and problem for energy improving, statistical analysis and get the conclusion. The results showed that the prevalence among the small businesses¡¦ waste of energy, there is many invalid lighting, it is the room to improve the installation of reflective shade to effect the lighting, even replace the lamps (T8) to lamps (T5) with reflective shade, then reduce the use of lamps and power, indirectly to reduce the power consumption of air condition. This research also found there is considerable room to improve the light in the refrigerated cabinet. The traditional fluorescent lamps(T8) be used in the refrigerated cabinet. The performance is low and produce high temperature, then the refrigerated cabinet shall expand more power to reach the set temperature, if change those lamps to LED lamps could immediately reduce the loss of electricity bills. Extension of this study, there is a great improvement in the domestic building and enterprises on lighting application, it could reduce a lot of power consumption by detailed observing, detected, and improving engineer to remove lighting waste, and thus achieve carbon reduction targets by 20% of the electricity.

This dissertation proposes a novel control technique for power density maximization of the brushless DC (BLDC) generator which is a nonsinusoidal power supply system. In a generator of given rating, the weight and size of the system affect the fuel consumption directly, therefore power density is one of the most important issues in a stand-alone generator. Conventional rectification methods cannot achieve the maximum power possible because of a distorted or unsuitable current waveform. The optimal current waveform for maximizing power density and minimizing machine size and weight in a nonsinusoidal power supply system has been proposed theoretically and verified by simulation and experimental work. Also, various attributes of practical interest are analyzed and simulated to investigate the impact on real systems.

The contents of this work investigate the capability of integrating the PT in applications by invoking the ratio of the throughput power to volume represented by the term: power density. The fundamentals of the PT are introduced in chapter two. In chapter three, the fundamental limitations of the PT's capability of transferring power to the load are studied. There are three major limitations: temperature rise due to losses during operation, electromechanical limits of material, and interactions with output rectifier. The analysis and estimation are then verified by experiments and calculations implemented on three different PT samples fabricated from three different manufacturers. The subject of chapter four is the behavior of the PT's power amplifier. This chapter concentrates on two main amplifier topologies, optimized based on the simplicity of structure and minimization of components (passive and active): class D and class E amplifiers. The operational characteristics of these amplifiers with the PT are then comparison. Methods to track the optimum frequency and discontinuous working mode of the PT are proposed as the approaches to improve the energy transfer of the PT. In chapter five, prototypes of four devices using a PT are developed and introduced as illustrations of the integration of PTs into practical applications: an igniter for high intensity discharge (HID) lamps, high DC voltage power supplies, and electronic ballasts for LEDs, and stand-alone ionizers for food sterilizers. Some concluding statements and ideas for future works are located in the last chapter - chapter six.

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