1,720,952 research outputs found
AC Loss Modeling of Superconducting Field Windings for a 10MW Wind Turbine Generator - an Analytical and Numerical Analysis
No full textThe total installed capacity of wind turbines is growing as society moves towards a more sustainable energy supply. With the integration of more wind turbines in the grid the price and reliability of future wind turbines are very important. One of the promising drive train topologies currently investigated is the direct drive superconducting wind turbine. This configuration allows for higher reliability, less top mass and nearly full independence of the volatile market of rare earth metals. However, the superconducting windings in such a generator operate only at cryogenic temperatures which is a challenge in the design of the machine. Since superconducting windings operate at a very low temperature it is important to estimate the heat generation in the windings. AC loss is the main cause of heat generation in a superconducting field winding. This thesis attempts to analyse the AC loss in two 10MW superconducting generator designs using analytical and numerical modeling. After introducing the problem description, the theory concerning AC loss in superconducting wires is treated. Then, the methods for both modeling techniques are established and partly validated. The results are then shown and discussed after which the conclusions are drawn. Both generators are designed for the same turbine and therefore have the same rotational speed and rated power which makes them comparable. The geometry however is different and as the results will show, these differences in design result in major differences in AC loss. Depending on machine geometry the analytically calculated AC loss is ranging from 22.2W to 283W in the Non Magnetic Teeth (NMT) design and 0.7kW to 2.9kW in the Iron Teeth (IT) design. The numerically calculated hysteresis loss is on average 154W in the NMT machine and 371W in the IT machine.Sustainable Energy TechnologyElectrical Power EngineeringElectrical Engineering, Mathematics and Computer Scienc
Saddle add-on metallization for RF-IC technology
No full textElectrical Engineering, Mathematics and Computer Scienc
Material-Inversion Solid-Phase Epitaxy of p+ Si forElevated Junctions
No full textMicroelectronicsElectrical Engineering, Mathematics and Computer Scienc
Enhancement of AlN Slender Piezoelectric Cantilevers Actuation by PECVD Silicon Nitride Coating
No full textActuation enhancement for AlN piezoelectric cantilevers is achieved by coating slender AlN beams with a thin PECVD silicon nitride (SiN) layer. Very good linearity and high deflection, up to 19 nm/V of actuation deflection for 200 ?m long cantilevers, at quasi-static mode, is obtained for a 500 nm SiN top layer. This value is three times larger than our previously reported value for cantilevers without the SiN layer. The achieved results make these cantilevers, fabricated in a CMOS compatible process, very promising micro/nano actuators.Delft Institute of Microsystems and NanoelectronicsElectrical Engineering, Mathematics and Computer Scienc
High-resistivity nanogranular Co–Al–O films for high-frequency applications
No full textThis work presents a series of high-resistivity nanogranular Co–Al–O films with maximum resistivity of ? 110?m??cm. The films were deposited using pulsed dc reactive sputtering of a Co72Al28 target in an oxygen/argon ambient. The samples were characterized by scanning electron microscopy (SEM), M-H loop measurements, and s-parameter measurements on microstrip transmission lines with Co–Al–O magnetic cores. The high-frequency magnetic permeability profile was extracted from the microstrip measurements. Reduction of deposition power resulted in resistivity enhancement, as well as reduction of coercivity and permeability. SEM images reveal an average grain size of ? 80?nm for films with the highest resistivity.DIMESElectrical Engineering, Mathematics and Computer Scienc
Going Beyond Counting First Authors in Author Co-citation Analysis
Get PDFThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Magnetic-Multilayered Interconnects Featuring Skin Effect Suppression
No full textA novel concept for a high-frequency, low-loss interconnect with significant skin effect suppression over a wide frequency band is presented. The concept is based on a multilayer comprising thin magnetic (Ni80Fe20) and metal (Cu) layers. The negative permeability of the magnetic layers leads to a nearcancellation of the overall permeability of the multilayer stack. This results in a significant increase of skin depth and thus, a more uniform distribution of the current density and a dramatic reduction of loss within a certain frequency range. Coplanar waveguides built using the multilayer technology show more than 50% loss reduction at 14 GHz compared to their thick Cu-based counterparts.Delft Institute of Microsystems and NanoelectronicsElectrical Engineering, Mathematics and Computer Scienc
Silicon micromachining of high aspect ratio, high-density through-wafer electrical interconnects for 3-D multichip packaging
No full textElectrical Engineering, Mathematics and Computer Scienc
Sub-500/spl deg/C solid-phase epitaxy of ultra-abrupt p/sup +/-silicon elevated contacts and diodes
No full textElectrical Engineering, Mathematics and Computer Scienc
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