619 research outputs found
Advanced Integrated Power and Attitude Control System (IPACS) study
Integrated Power and Attitude Control System (IPACS) studies performed over a decade ago established the feasibility of simultaneously satisfying the demands of energy storage and attitude control through the use of rotating flywheels. It was demonstrated that, for a wide spectrum of applications, such a system possessed many advantages over contemporary energy storage and attitude control approaches. More recent technology advances in composite material rotors, magnetic suspension systems, and power control electronics have triggered new optimism regarding the applicability and merits of this concept. This study is undertaken to define an advanced IPACS and to evaluate its merits for a space station application. System and component designs are developed to establish the performance of this concept and system trade studies conducted to examine the viability of this approach relative to conventional candidate systems. It is clearly demonstrated that an advanced IPACS concept is not only feasible, but also offers substantial savings in mass and life-cycle cost for the space station mission
Design of a permanent magnet axial flux high-speed generator
Electrical generating sets powered by gas turbines are required for many
applications, in particular for emergency situations due to their critical attributes; high
reliability, lightweight, small size, multi-fuel capabilities, low maintenance, low noise
and low gas emissions.
This research contends that a permanent magnet axial flux (PMAF) high-speed
generator with a small gas turbine engine offers advantages over the radial flux
permanent magnet generators. Higher power densities can be achieved with the axial
flux configuration when compared to their counter parts of the radial flux machines of
similar output power. The attributes of the PMAF machines were certainly appealing;
lightweight, small size, high efficiency and ease of construction.
In this research, a design approach for the PMAF high-speed generator which
accounts for the mechanical and electrical aspects was provided. The machine's key
components such as retainment ring was carefully designed and the materials utilised
in their structures were appropriately selected to insure high mechanical integrity, ease
of construction and low manufacturing cost. The generator's principle dimensions
were determined from a theoretical model which was derived from the machine's main
design parameters. This theoretical model was then correlated by some empirical
coefficients determined through the manipulation of the experimentally validated finite
element (FE) results. The analytical results have shown that with the appropriate
design considerations, PMAF high-speed generators can be designed with high power
densities in the range of 6-8 kW/kg and high efficiencies ideally in the range of 94 -
96 %. The mechanical integrity and the steady state electrical performance of the
machine were analysed using three-dimensional (3D) FE models. More in this
research, a parametric study was carried out on the most influential parameters of the
machine to improve its electrical performance through minimise rotor and stator eddy
current losses. In addition, the total harmonic distortion in the output waveform was
minimised through the appropriate and careful design of the magnet shape and
topology with the aid of 3D electromagnetic FE analysis. Furthermore, using FE it
was possible to design, optimise and analyse the rotor back-iron disc through the
selection of best material, shape and size for use in the PMAF high-speed generator. A
prototype of the PMAF high-speed generator was constructed and tested preliminary at
low speed for the purpose of the evaluation of the electrical performance of the
machine. Experimental results have shown that the machine was capable to meet the
design requirements. For the mechanical integrity of the machine, the rotors were
safely tested on a cold run test rig at the speed of 47,000 rpm. This thesis describes
also the trends and the technical details in the manufacturing, construction and
experimental setup for the PMAF high-speed generator
New Energy Harvesting Systems Based on New Materials
This study starts with the ZnO nanostructured materials used for improve the efficiency of polycrystalline solar cells operation under low solar radiation conditions. The ZnO nanowires were prepared using the hydrothermal method of deposition on the seed layer by a new and complex process, with controllable morphological and optical properties. The analysis of the XRD patterns, scanning electron microscopy images (SEM) of the ZnO nanowires and a lot of tests made Pasan Meyer Burger HighLight 3 solar simulator, confirm the advantages of using the ZnO nanowires in solar cells applications for antireflection coatings. Then, piezoelectric structures based on new modified PZT zirconate titanate designed for energy harvesting applications is presented. Based on their piezoelectric characteristics, modified PZT zirconate titanate ceramics made of Pb(Zr0.53Ti0.47)0.99Nb0.01O3 ceramic have efficient applications in energy harvesting devices. A piezoelectric transducer, consisting of a thin plate of this piezoceramic material, with dimensions (34 mm × 14 mm × 1 mm), is illustrated. A multiphysics numerical simulation further illustrates such piezoelectric transducer operation. Finally, the miniature planar transformer with circular spiral winding and hybrid core—ferrite and magnetic nanofluid, designed for new energy harvesting systems is presented. We purpose now that the magnetic nanofluid be used both as a coolant and as part of the hybrid magnetic core
A Review of Transverse Flux Machines Topologies and Design
High torque and power density are unique merits of transverse flux machines (TFMs). TFMs are particularly suitable for use in direct-drive systems, that is, those power systems with no gearbox between the electric machine and the prime mover or load. Variable speed wind turbines and in-wheel traction seem to be great-potential applications for TFMs. Nevertheless, the cogging torque, efficiency, power factor and manufacturing of TFMs should still be improved. In this paper, a comprehensive review of TFMs topologies and design is made, dealing with TFM applications, topologies, operation, design and modeling
A review on power electronics technologies for electric mobility
Concerns about greenhouse gas emissions are a key topic addressed by modern societies worldwide. As a contribution to mitigate such effects caused by the transportation sector, the full adoption of electric mobility is increasingly being seen as the main alternative to conventional internal combustion engine (ICE) vehicles, which is supported by positive industry indicators, despite some identified hurdles. For such objective, power electronics technologies play an essential role and can be contextualized in different purposes to support the full adoption of electric mobility, including on-board and off-board battery charging systems, inductive wireless charging systems, unified traction and charging systems, new topologies with innovative operation modes for supporting the electrical power grid, and innovative solutions for electrified railways. Embracing all of these aspects, this paper presents a review on power electronics technologies for electric mobility where some of the main technologies and power electronics topologies are presented and explained. In order to address a broad scope of technologies, this paper covers road vehicles, lightweight vehicles and railway vehicles, among other electric vehicles.This work has been supported by FCT – Fundação para a Ciência e Tecnologia with-in the Project Scope:
UID/CEC/00319/2020. This work has been supported by the FCT Project DAIPESEV PTDC/EEI-EEE/30382/2017, and by the FCT Project new ERA4GRIDs PTDC/EEI-EEE/30283/2017. Tiago Sousa is supported by the doctoral scholarship SFRH/BD/134353/2017 granted by FCT
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