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Dissertations / Theses on the topic 'Electric currents'
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Haddad, Peter Alexander. "Biofilm Treatments with Electric Currents." Thesis, Université d'Ottawa / University of Ottawa, 2014. http://hdl.handle.net/10393/30947.
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The Problem: Biofilms are a community of bacteria that cause infections which are resistant to the immune system and antimicrobial treatments, posing a significant threat for patients with implantable and indwelling medical devices. Purpose: The purpose of this research is to effectively treat biofilms utilizing electric currents assisted by antibiotics. Method: Evaluated the impact of direct electric current with or without vancomycin against Staphylococcus epidermidis biofilms. Results: (1) Electric current reduced the S. epidermidis biofilm and (2) increased the effectiveness of vancomycin. (3) Older biofilms had an increased resistance to vancomycin treatments. (4) Higher electric current intensities and (5) longer duration treatments were more effective against biofilms. Conclusion: Electric current increased the effectiveness of vancomycin against S. epidermidis biofilms.
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Díaz, Santiago Sebastián Alejandro. "Controlling Spin Interactions With Electric Currents." Tesis, Universidad de Chile, 2010. http://www.repositorio.uchile.cl/handle/2250/102410.
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Cappelle, Sabine. "Possible ionospheric electric currents for PI2 Micropulsations." Thesis, University of British Columbia, 1986. http://hdl.handle.net/2429/26179.
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Two possible ionospheric electric currents for Pi2 micropulsations are investigated and tested against data collected from a meridian chain of stations in Saskatewan.
The electric coupling between the ionosphere and the magnetosphere under disturbed magnetospheric conditions is believed to be the cause of the Pi2 generation and propagation.
The LC circuit analogy is first used to model this interaction, the source of energy lying in the magnetospheric equatorial plane. Secondly, the possibility of an ionospheric electric impulse imparted to a field-aligned current under the conditions of brightening of aurora is considered.
It is found experimentally that the Pi2 originates possibly from these two source regions: the characteristics of a resonant LC oscillation expanding symmetrically to the west and to the east of the magnetospheric potential source are observed, as well a strong toroidal field existing and possibly originating in the ionosphere.
It is suggested that optical data in conjunction with auroral radar echo and satellite data be necessary to confirm a future mathematical development of these possible Pi2 generation and propagation models.Science, Faculty of
Earth, Ocean and Atmospheric Sciences, Department of
Graduate
4
Johansson, Tommy. "Investigations of auroral electric fields and currents." Doctoral thesis, Stockholm : Elektro- och systemteknik, Kungliga Tekniska högskolan, 2007. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-4512.
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Wilson, Thomas Lawler. "A multi-coil magnetostrictive actuator." Diss., Atlanta, Ga. : Georgia Institute of Technology, 2009. http://hdl.handle.net/1853/28243.
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Thesis (M. S.)--Mechanical Engineering, Georgia Institute of Technology, 2009.Committee Chair: Zinn, Ben T.; Committee Member: Book, Wayne; Committee Member: Glezer, Ari; Committee Member: Neumeier, Yedidia; Committee Member: Seitzman, Jerry.
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Patel, Ashaben Mehul. "Current measurement in power electronic and motor drive applications - a comprehensive study." Diss., Rolla, Mo. : University of Missouri-Rolla, 2007. http://scholarsmine.mst.edu/thesis/pdf/Patel_09007dcc8042b818.pdf.
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Thesis (M.S.)--University of Missouri--Rolla, 2007.Vita. The entire thesis text is included in file. Title from title screen of thesis/dissertation PDF file (viewed February 5, 2008) Includes bibliographical references (p. 96-109).
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Lu, Shu. "Power transformer magnetization under GIC/GMD." Diss., This resource online, 1994. http://scholar.lib.vt.edu/theses/available/etd-09232008-144706/.
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Hänninen, Seppo. "Single phase earth faults in high impedance grounded networks : characteristics, indication and location /." Espoo [Finland] : Technical Research Centre of Finland, 2001. http://www.vtt.fi/inf/pdf/publications/2001/P453.pdf.
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Swafford, Robert D. "Development of a new generation of electric current sensors through advances in manufacturing techniques and material design." Diss., Georgia Institute of Technology, 2013. http://hdl.handle.net/1853/50306.
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Electrical systems have become ubiquitous, and with them come the need to
accurately monitor electric current. The aerospace industry is no exception. Modern
aircraft may contain more than one hundred current sensors, each one critical to a
properly functioning vehicle. While these sensors function acceptably, several areas
have been identified for improvement: size, weight, and cost. Each sensor is bulky,
taking up valuable space. They are also costly to manufacture. The existing design
is based on the Hall effect, and has remained fundamentally unchanged for decades.
With the recent progress in manufacturing techniques and materials, it would be beneficial
to reexamine these sensors and determine if improvements can be made using
the accomplishments of recent years. Of particular interest are microelectromechanical
systems, also known as MEMS. Using a sensor based on MEMS technologies in
which design, function, and fabrication are closely intertwined would automatically
meet two of the three goals: reducing size and weight. MEMS additionally have the
potential to allow existing systems to be miniaturized. Also of interest are advanced
materials, some of which can behave as transducers, linking different physical phenomenon.
The goal of this dissertation is to use advances in manufacturing techniques
and materials, specifically those discussed above, to design a better current sensor.
As part of this goal, several potential solutions were studied and optimized. Finally,
proof-of-concept prototypes were fabricated and tested to validate the feasibility of
the designs and offer insight into continued sensor development.
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Kletsov, Aleksey. "Electron propagator and surface Green's function calculations in transport molecular junctions." Laramie, Wyo. : University of Wyoming, 2007. http://proquest.umi.com/pqdweb?did=1445047011&sid=12&Fmt=2&clientId=18949&RQT=309&VName=PQD.
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Javanshir, Marjan. "DC distribution system for data center." Thesis, Click to view the E-thesis via HKUTO, 2007. http://sunzi.lib.hku.hk/hkuto/record/B39344952.
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Brown, Robert Ernest. "Investigation of disintegration and arcing in electric fuses." Thesis, Sheffield Hallam University, 2000. http://shura.shu.ac.uk/7111/.
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This thesis essentially presents the experimental investigation of the fundamental phenomena of electric fuse element disintegration and its causation and influence on the subsequent fragmentation of the fuse elements when subjected to excessive fault currents. The basis of the study involved experimental observation of disintegration of fuse elements and the analysis of the dynamic responses of current-carrying conductors, which precipitate disintegration. The experimental techniques employed utilised commercially available video cameras to capture images of element disruptions during disintegration of fuse elements subjected to low short-circuit and high overload currents. Specialist experimental image capturing techniques and hardware implementations were developed to enable investigation of element disintegration caused by high short-circuit fault currents. Disintegration phenomena of fuse elements for all fault cases were compared within different time domains, which included specialist techniques to investigate disintegration of elements in sand and against glass substrates. Disintegration phenomena of elements in unconfined media such as air and water also constituted the studies. The studies diverged, finally, into experimental observations of the temporal development of arc initiation and extinction phenomena of fault current limiting of HBC fuses using spectroscopic analysis of the arc light radiation. The range of studies covered have led to new understandings of fundamental current limiting behaviour of HBC and open type fuses which contribute, in a small way, to the knowledge base of the subject and hopefully will be an aid to improved designs and development of new types of electric fuse.
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Manna, Tapan K. "Impulse impedance of grounding systems and its effect on tower crossarm voltage : a dissertation presented to the faculty of the Graduate School, Tennessee Technological University /." Click to access online version, 2006. http://proquest.umi.com/pqdweb?index=97&did=1208141981&SrchMode=1&sid=1&Fmt=6&VInst=PROD&VType=PQD&RQT=309&VName=PQD&TS=1256323226&clientId=28564.
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Papalexopoulos, Alexis D. "Modeling techniques for power system grounding systems." Diss., Georgia Institute of Technology, 1985. http://hdl.handle.net/1853/13529.
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Chen, Chuen-Song. "On-chip current and power measurement techniques for integrated circuits with regulated power /." View online ; access limited to URI, 2008. http://0-digitalcommons.uri.edu.helin.uri.edu/dissertations/AAI3314451.
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Zhang, Yunhu. "Grain refinement in hypoeutectic Al-Si alloy driven by electric currents." Doctoral thesis, Technische Universitaet Bergakademie Freiberg Universitaetsbibliothek "Georgius Agricola", 2016. http://nbn-resolving.de/urn:nbn:de:bsz:105-qucosa-197915.
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The present thesis investigates the grain refinement in solidifying Al-7wt%Si hypoeutectic alloy driven by electric currents. The grain size reduction in alloys generated by electric currents during the solidification has been intensively investigated. However, since various effects of electric currents have the potential to generate the finer equiaxed grains, it is still argued which effect plays the key role in the grain refinement process. In addition, the knowledge about the grain refinement mechanism under the application of electric currents remains fragmentary and inconsistent. Hence, the research objectives of the present thesis focus on the role of electric current effects and the grain refinement mechanism under the application of electric currents.
Chapter 1 presents an introduction with respect to the subject of grain refinement in alloys driven by electric current during the solidification process in particular, including the research objectives; the research motivation; a brief review about the research history; a short introduction on the electric currents effects and a review relevant to the research status of grain refinement mechanism.
Chapter 2 gives a description of research methods. This chapter shows the employed experiment materials, experimental setup, experimental procedure, the analysis methods of solidified samples, and numerical method, respectively.
Chapter 3 focuses on the role of electric current effects in the grain refinement process. A series of solidification experiments are performed under various values of effective electric currents for both, electric current pulse and direct current. The corresponding temperature measurements and flow measurements are carried out with the increase of effective electric current intensity. Meanwhile, numerical simulations are conducted to present the details of the flow structure and the distribution of electric current density and electromagnetic force. Finally, the role of electric current effects is discussed to find the key effect in the grain refinement driven by electric currents.
Chapter 4 investigates the grain refinement mechanism driven by electric currents. This chapter mainly focuses on the origin of finer equiaxed grain for grain refinement under the application of electric current on account of the importance of the origin for understanding the grain refinement mechanism. A series of solidification experiments are carried out in Al-7wt%Si alloy and in high purity aluminum. The main origin of equiaxed grain for grain refinement is concluded based on the experiment results.
Chapter 5 presents three further investigations based on the achieved knowledge in chapter 3 and 4 about the role of electric current effects and the grain refinement mechanism. According to the insight into the key electric current effect for the grain refinement shown in chapter 3, this chapter presents a potential approach to promote the grain refinement. In addition, the solute distribution under the influence of electric current is examined based on the knowledge about the electric current effects. Moreover, the grain refinement mechanism under application of travelling magnetic field is investigated by performing a series of solidification experiments to compare with the experiments about the grain refinement mechanism driven by electric currents shown in chapter 4.
Chapter 6 summarizes the main conclusions from the presented work.
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Heger, Walter. "Using the finite difference and the finite element method to solve an electric current diffusion problem." Thesis, McGill University, 1987. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=66150.
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Somhlahlo, Nomabali Nelisiwe. "A Hall-effect study of as-grown and hydrogenerated n-type ZnO layers grown by MOCVD." Thesis, Nelson Mandela Metropolitan University, 2006. http://hdl.handle.net/10948/444.
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A series of as-grown ZnO layers have been electrically characterised by the temperature dependent (20 – 300 K) Hall-effect technique. The ZnO layers were grown by metal organic chemical vapour deposition (MOCVD) on glass substrates under various growth conditions. The temperature dependent Hall-effect technique produced mobility and carrier concentration measurements. These measurements were found to be reproducible and reliable. The carrier concentration data for the layers was fitted by the charge balance equation to accurately determine the donor level and corresponding donor concentration as well as the acceptor concentration for each sample. The measured donor levels were found to vary from sample to sample and there is evidence from the results that the variations are related to the differing growth conditions of the layers. The mobility data was also fitted to establish the dominant electron scattering mechanisms in the layers. The dominant scattering mechanisms were found to vary from sample to sample. For most of the layers studied, the dominant scattering mechanism was found to be both the ionised impurity scattering at low temperatures (20 – 100 K) and grain boundary scattering at higher temperatures (100 – 300 K). The effects of exposing the ZnO layers to hydrogen plasma were also investigated by the temperature dependent Hall-effect technique. Findings indicate that hydrogen is readily incorporated in ZnO, leading always to an increased carrier concentration. It was further noted that incorporating hydrogen into ZnO in some layers increased the mobility while in other layers it caused a decrease in the mobility. The hydrogenated samples were subsequently annealed at 600 °C for 1 hour in argon ambient resulting in the carrier concentration reducing to its original value. This effect is attributed to hydrogen diffusing out of ZnO.
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Tsang, Tony Ka Leong. "Low power weak current processing for weak biomedical applications /." View abstract or full-text, 2008. http://library.ust.hk/cgi/db/thesis.pl?ECED%202008%20TSANG.
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Teschan, Paul Erhard. "Determination of lightning characteristics through the use of electromagnetic field data." Thesis, The University of Arizona, 1990. http://hdl.handle.net/10150/277252.
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In this thesis we determine the electromagnetic fields of a current distribution located, in free space, above a perfectly conducting plane earth. Then we consider the inverse problem of determining the source distribution from the fields. Formulae are obtained for the volume integral (dipole moment) of the current density of a small current source in terms of the fields and known functions. If field data are measured (from lightning over sea water for example) the dipole moment of the current density producing the fields may be found. The validity of the small source approximation used in this work is also established. Finally, a method is developed for determining the average current at points on a vertical line current source, a common model for a lightning return stroke. We treat the source as a string of dipoles and apply a method of constrained inversion.
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Tong, Sai-kit. "A computer-aided measurement system for monopolar high-voltage direct-current coronating lines /." [Hong Kong] : University of Hong Kong, 1986. http://sunzi.lib.hku.hk/hkuto/record.jsp?B12321771.
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Zhang, Lei, and 張磊. "First principle calculation: current density in AC electric field." Thesis, The University of Hong Kong (Pokfulam, Hong Kong), 2009. http://hub.hku.hk/bib/B43278437.
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Zhang, Lei. "First principle calculation : current density in AC electric field /." Click to view the E-thesis via HKUTO, 2009. http://sunzi.lib.hku.hk/hkuto/record/B43278437.
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Pei, Ruilin. "Measurement and analysis of critical current and AC loss of HTS tapes in a superconducting machine." Thesis, University of Cambridge, 2010. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.609019.
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Prabhakaran, Pradeep. "Development of electronic instrument for defect measurements with eddy currents /." St. Lucia, Qld, 2004. http://www.library.uq.edu.au/pdfserve.php?image=thesisabs/absthe17873.pdf.
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郭榮忠 and Wing-chung Kwok. "Current conserving AC quantum transport in two-dimensional mesoscopic systems." Thesis, The University of Hong Kong (Pokfulam, Hong Kong), 1999. http://hub.hku.hk/bib/B3122104X.
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Gupta, D. K. "Transportation of ferromagnetic powder using linear motor devices." Thesis, Loughborough University, 1994. https://dspace.lboro.ac.uk/2134/9219.
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The travelling magnetic wave of a linear induction motor induces eddy currents in a secondary circuit (usually a sheet consisting at least partly of a non-magnetic metal, often aluminium), which cause the unrestrained member to move linearly in the direction of the travelling wave. A linear motor can also transport ferromagnetic powder, although this travels in the opposite direction to the travelling magnetic field. The motion is therefore due to a mechanism other than the eddy currents flowing in the sheet secondary. Expressions for the forces acting on an iron particle due to a travelling magnetic field are derived in the thesis. Preliminary experiments support the assumptions made in the derivations of the force expressions and lead to the formation of an hypothesis. This is shown to be capable of predicting both linear and rotational particle speeds and, with greater accuracy, the distance travelled and the rotation experienced by the particles. Experiments conducted on tubular and transverse flux motors have enabled different linear motors to be identified as suitable for a number of powder transportation applications. The results obtained show also the importance of large flux density values, the tangential to normal flux density ratio and large pole-pitch winding arrangements, with the latter lending support to the original hypothesis. The results of a finite element investigation of the tubular motor did not closely agree with the results from the experimental motor although similar trends were evident. Flux density values within particles were found to be considerably greater than those outside, as assumed in the hypothesis.
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Abbas, Al-Byati N. "The eddy-current damping of synchronous machines with solid cylindrical rotors." Thesis, University of Southampton, 1989. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.330125.
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Kwok, Wing-chung. "Current conserving AC quantum transport in two-dimensional mesoscopic systems /." Hong Kong : University of Hong Kong, 1999. http://sunzi.lib.hku.hk/hkuto/record.jsp?B20668065.
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Khan, Atif Zaman. "Eigenvalue sensitivites and their applications to power system voltage stability." Diss., Georgia Institute of Technology, 1993. http://hdl.handle.net/1853/13911.
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Cheng, Carol Shaoyu. "A hybrid approach to power system voltage security assessment." Diss., Georgia Institute of Technology, 1991. http://hdl.handle.net/1853/15469.
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Gammon, Tammy Lea. "Improved arcing-fault current models for low-voltage power systems (<1kV)." Diss., Georgia Institute of Technology, 1999. http://hdl.handle.net/1853/15675.
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Ryan, D. T. "Critical currents of commercial superconductors in the picovolt per metre electric field regime." Thesis, University of Oxford, 1997. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.242036.
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湯世傑 and Sai-kit Tong. "A computer-aided measurement system for monopolar high-voltage direct-current coronating lines." Thesis, The University of Hong Kong (Pokfulam, Hong Kong), 1986. http://hub.hku.hk/bib/B31207467.
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Maffitt, Kenneth F. "Alternating currents in Mexican labor : electrical manufacturing workers in Mexico City, 1968-1986 /." Diss., Connect to a 24 p. preview or request complete full text in PDF format. Access restricted to UC campuses, 2000. http://wwwlib.umi.com/cr/ucsd/fullcit?p9975040.
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Manore, Jean L. "Cross-currents: The development of the hydro-electric system in northeastern Ontario, 1911-1966." Thesis, University of Ottawa (Canada), 1995. http://hdl.handle.net/10393/10000.
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Examining hydro-electric development, as it occurred in northeastern Ontario, sheds a new and different light on the history of technology and development in Canada. The northeastern Ontario hydro-electric system (Mattagami and Abitibi watersheds) developed over a period of fifty years. It developed through a process of interaction between technology and the environment, native and non-native relations, metropolitan business and political interests and northern natural resources. Once Aboriginal rights and environmental obstacles had been removed through treaty negotiations and technical innovations, early hydro-electric development took place under private auspices by individual entrepreneurs such as Frank Cochrane or big concerns such as Nesbitt Thomson, operating out of Montreal. Their activities, for the most part, established a series of independent generating stations serving specific customers in northeastern Ontario, with some interconnection with Quebec. After 1944, with the entry of Ontario Hydro into northeastern Ontario and the elimination of Nesbitt Thomson and other private developers, the amalgamation of the northeastern Ontario system into the southern Ontario system began in earnest. Amalgamation resulted from the interweaving of various factors not the least of which was continued drought in the northeast rendering the system incapable of supplying the region's power needs. Studying the influence of rivers on the development of technical systems proves that nature does interact with technology and therefore should not be ignored. In the example provided by this dissertation, the river influences the shape of the hydro-electric system significantly. Studying the interaction between hydro-electric developers, the environment and First Nations illustrates that, even though they are harmed by development, the latter two actors are not helpless. To portray them as victims denigrates their ability to shape development and adapt to adverse conditions. Also, studying the interaction between the metropole and the northeastern region demonstrates that the hinterland is more than a backdrop to metropolitan development. It too influences the decisions of the metropolitan systems builders. Because the hinterland, the environment and the First Nations retain their own identity and shape the system's development, the metaphor used to describe systems development should acknowledge turmoil or conflict but additionally convey an image of adaptation and continuity; hence the metaphor of cross-currents. Turmoil occurs when cross-currents intersect in a river's course but this act of intermingling also includes adaptation thus allowing for continuity. Including the rivers themselves in the study of hydro-electric development also illuminates a feature of development that has rarely been discussed: co-operation. In the northeast, co-operation in certain areas proved necessary to allow and further the hydro-electric system's growth. This element of co-operation is a timely characteristic to note. In today's environment of limited energy resources, increasing criticism of the ideology of "Progress" and increasing respect for First Nations' rights and the environment, co-operation is a more acceptable approach to development than conquest and domination. (Abstract shortened by UMI.)
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Wills, Dominic. "Methods to quantify and reduce rotor losses in a solid rotor yoke permanent magnet machine." Thesis, Stellenbosch : University of Stellenbosch, 2010. http://hdl.handle.net/10019.1/4014.
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Thesis (PhD (Electrical and Electronic Engineering))--University of Stellenbosch, 2010.ENGLISH ABSTRACT: Certain types of electric machines are particularly susceptible to the proliferation of eddy currents flowing within the solid conducting regions in the rotor. Single-layer, non-overlapping windings within uneven open slots are some stator properties that can produce damaging, asynchronous magnetic field harmonics which manifest in the rotor as eddy currents. The ohmic losses caused by these eddy currents are a source of inefficiency and can cause a marked increase in the temperature of the rotor. This temperature rise can be dangerous for the magnets, which have to be kept within temperature limits to avoid partial or full demagnetization. The research work presented here is concerned with reducing the effect of eddy currents in the rotor magnets and solid rotor yoke of an electric machine. The work presents analytical methods to calculate the magnetic fields, eddy currents and solid loss in an electric machine due to current in the winding and due to the interaction of the permeance variation in the stator with the magnets in the rotor. A method is also suggested where the analytical theory can be used with a magnetostatic finite element solution to produce a transient solid loss result. The research work also investigates a method for optimal segmentation in both level and penetration, and provides some design suggestions. The work presents the method of partial magnet segmentation, which is a technique whereby thin incisions are made into the magnet material from one or both sides. Another method of partial rotor segmentation is also presented where the incisions are made into a portion of the magnet-facing solid yoke. These methods attempt to interrupt the flow of eddy currents and increase the resistance ‘seen’ by the eddy currents, while also keeping construction difficulty and cost to a minimum. The methods are verified using finite element calculations which are compared to measured results. The result is that partial magnet segmentation is a very useful, effective and practical method of segmenting magnets. The loss reduction profile can be similar to that of traditional full segmentation. The method of partial rotor segmentation also shows a large reduction in rotor power loss. With implementation of these methods on a test machine, one can expect an efficiency increase of more than 4 %
AFRIKAANSE OPSOMMING: Sekere tipes van elektriese masjiene is veral sensitief vir die vloei van werwelstrome in solied geleidende gebiede in die rotor. Enkellaag, nie-oorvleuelende wikkelings in oneweredige oop gleuwe is enkele stator eienskappe wat skadelike, asinchrone magneetveld harmonieke tot gevolg kan hê, wat as werwelstrome in die rotor manifesteer. Die ohmiese verliese wat deur hierdie werwelstrome teweeg gebring word is 'n bron van ondoeltreffendheid en kan lei tot 'n merkbare toename in die temperatuur van die rotor. Hierdie temperatuur styging hou gevaar in vir die magnete en moet binne temperatuur limiete gehou word om gedeeltlike of self volle demagnetisering te vermy. Die navorsing vervat in hierdie document is gemoeid met die vermindering van die effek van werwelstrome in die rotor magnete en in die soliede rotor juk van 'n elektriese masjien. Die werk bied analitiese metodes aan vir die berekening van die magneetvelde, werwelstrome en soliede verliese in ’n elektriese masjien as gevolg van strome in die wikkelings en die interaksie van die permeansie variasie van die stator met die magnete in die rotor. ’n Metode word ook voorgestel waar die analitiese teorie saam met ’n magnetostatiese eindige element oplossing gebruik word om ’n resultaat vir die oorgang soliede verliese te verkry. Die navorsingswerk ondersoek ook ’n metode vir die optimale segmentering in beide vlak sowel as penetrasie, en verskaf sekere ontwerp voorstelle. Die werk bied die metode aan van gedeeltelike magneet segmentering, wat 'n tegniek is waarvolgens dun insnydings gemaak word aan een of beide kante van die magneet materiaal. Nog ’n metode van gedeeltelike rotor segmentering word beskou waar die insnydings in in ’n gedeelte aan die magneetkant van die soliede rotor juk gemaak word. Hierdie metodes poog om die vloei van werwelstrome te onderbreek en die weerstand soos "gesien" deur die werwelstrome te verhoog, terwyl konstruksie kompleksiteit en koste tot ’n minimum beperk word. Die metodes word bevestig deur eindige element berekeninge wat met gemete resultate vergelyk word. Die gevolg is dat gedeeltelike magneet segmentering 'n baie nuttige, doeltreffende en praktiese metode van die segmentering van magnete is. Die verliesverminderingsprofiel van gedeeltelike segmentering kan soortgelyk wees aan dit van tradisionele volle segmentering. Die metode van gedeeltelike rotor segmentering toon ook 'n groot afname in rotor drywingsverlies. Met die implementering van hierdie metodes op ’n toetsmasjien, kan ’n mens ’n verhoging in benuttingsgraad verwag van meer as 4 %
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Matandirotya, Electdom. "Measurement and modelling of geomagnetically induced currents (GIC) in power lines." Thesis, Cape Peninsula University of Technology, 2016. http://hdl.handle.net/20.500.11838/2459.
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Thesis (DTech (Electrical Engineering))--Cape Peninsula University of Technology, 2016.Geomagnetically induced currents (GIC) are currents induced in ground-based conductor networks in the Earth's surface. The GIC are driven by an electric eld induced by geomagnetic variations which are a result of time-varying magnetospheric-ionospheric currents during adverse space weather events. Several studies have shown that there is a likelihood of technological damage (the power grid) in the mid- and low-latitude regions that could be linked to GIC during some geomagnetic storms over the past solar cycles. The effects of GIC in the power system can range from temporary damage (e.g. protective relay tripping) to permanent damage (thermal transformer damage). Measurements of GIC in most substations are done on the neutral-to-ground connections of transformers using Hall-effect transducers. However, there is a need to understand the characteristics of GIC in the power lines connected to these transformers. Direct measurements of GIC in the power lines are not feasible due to the low frequencies of these currents which make current measurements using current transformers (CT) impractical. This thesis discusses two techniques that can be employed to enhance understanding GIC characteristics in mid-latitude regions. The techniques involve the measurement of GIC in a power line using differential magnetometer measurements and modelling GIC using the finite element method. Low frequency magnetometers are used to measure magnetic felds in the vicinity of the power lines and the GIC is inferred using the Biot-Savart law. A finite element model, using COMSOL-Multiphysics, is used to calculate GIC with the measured magnetic field and a realistic Earth conductivity profile as inputs. The finite element model is used for the computation of electric field associated with GIC modelling.
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Babinet, Cyril. "Next generation of current sensors for aeronautics preliminary designs /." Thesis, Atlanta, Ga. : Georgia Institute of Technology, 2008. http://hdl.handle.net/1853/29709.
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Thesis (M. S.)--Mechanical Engineering, Georgia Institute of Technology, 2008.Committee Co-Chair: Dr. Jianmin Qu; Committee Co-Chair: Dr. Mohammed Cherkaoui; Committee Member: Dr. Christophe Giraud-Audine; Committee Member: Dr. Nico Declercq. Part of the SMARTech Electronic Thesis and Dissertation Collection.
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Butler, David Buchanan. "Spatial scales of geomagnetically induced currents in B.C. Hydro's power transmission system." Thesis, University of British Columbia, 1990. http://hdl.handle.net/2429/28926.
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Geomagnetically Induced Currents (GIC's) in B. C. Hydro's 500 kV transmission
system have in the past been responsible for the generation of harmonics of 60 Hz, system voltage drops, and misoperation of relay units. Characterization of the associated magnetic storms' spatial scales would further the understanding of GIC generation in the area, and allow advanced warning of potential problems in future power transmission projects.
Data collected in 1984 at four substations were analysed to determine lateral variations in geomagnetically induced earth surface electric fields. Inversion techniques were employed to find a variety of solutions that would reproduce the data.
Results suggested that the magnetic storms were larger than the area monitored,
and that resultant electric fields seen by a large portion of the transmission grid were uniform. Departures from this uniformity in other portions of the electric
field models were felt either to be due to earth induction effects, or in some cases, to be artifacts of the data analysis techniques.
An experiment designed to determine the controlling factors behind GIC's is outlined. Considerable effort would be required to explicitly determine all electric fields affecting the transmission systemScience, Faculty of
Earth, Ocean and Atmospheric Sciences, Department of
Graduate
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Markovic, Dejan. "Induced currents in gas pipelines due to nearby power lines." Access electronically, 2005. http://www.library.uow.edu.au/adt-NWU/public/adt-NWU20060807.155002/index.html.
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Deierling, Phillip Eugene. "Electrical and thermal behavior of Im7/977-3 Carbon fiber polymer matrix composites subjected to time-varying and steady electric currents." Thesis, University of Iowa, 2010. https://ir.uiowa.edu/etd/791.
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Electrical and thermal behavior of the carbon fiber polymer matrix composites subjected to time-varying and steady electric currents is studied. A fully automated experimental setup for real time measurements of the electric current, resistance, voltage, and temperature in carbon fiber polymer matrix composites has been developed. A series of electrical characterization tests on IM7/977-3 unidirectional and symmetric cross-ply composite laminates have been performed and the effects of electric current magnitude and duration, electrical resistance, and associated thermal effects have been investigated. It is determined that voltage-current relationship stays ohmic for up to 50 A steady currents, electrical resistance exhibits time-dependent behavior. It is also found that application of an electric current leads to a significant temperature rise in the composites that is a result of the intense Joule heat produced in the electrically conductive carbon fibers as well as in the composite-electrode contact.
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El, Husseini Bassam. "Streaming potential measurements in sulfide rich tailings." Thesis, McGill University, 2008. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=115872.
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In general, tailings dams are expected to seep. Anomalous seepage, especially when induced by internal erosion, is a major concern for owners and operators. The long established techniques for monitoring water seepage provide sparse information which may not be sufficient to detect and map the seepage path. Hence, there exists a great need for non-invasive techniques that would be sensitive to changing seepage conditions. The non-invasive nature of the techniques is particularly important because drilling and other penetrating (invasive) investigation methods are normally avoided.Non-invasive techniques such as self-potential and high-resolution resistivity have been significantly improved in the past decade and have been successfully used for water retention dam investigation and monitoring. The main difficulty in the use of these techniques in monitoring sulfide rich tailings dams is the presence of electrochemical potentials that renders the interpretation of the acquired self-potential data difficult.
Numerical modelling is one of the latest methods in interpreting self-potential anomalies induced by liquid flow. But, in order to model streaming potentials several parameters need to be measured or estimated; (1) the hydraulic driving force and the hydraulic conductivity are required to solve for the hydraulic pressure distribution; (2) the cross-coupling conductivity distribution is needed to calculate the conduction current source parameter; and (3) the resistivity distribution is needed to determine the resulting potential distribution.
The zeta-potential and the resistivity of three pyrite rich tailings from the Abitibi region in Quebec were measured over the pH range 2 to 5 in different KCl aqueous solutions for the purpose of estimating the magnitude of electrokinetic effect induced by mine water seepage and the electrical resistivity variation induced by particle migration. The experimental and theoretical results obtained in the present study are pertinent to the interpretation of self-potential data. The zeta-potential was found to vary from -27 to -2 mV and the resistivity of the tailings was found to increase when fine particles are eroded.
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Ajitkumar, Rohit. "An analysis of DC distribution systems." Thesis, Georgia Institute of Technology, 2011. http://hdl.handle.net/1853/39590.
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The Master's Thesis research focuses on analyzing the possibilities of using Direct Current distribution systems to distribute power to end users. Considering the shift in load types in the past few decades and also a growing demand of distributed generation, DC distribution can potentially offer higher efficiencies and cost savings to utilities. The incorporation of DC distribution offers the opportunity to eliminate multiple conversion stages for devices which are powered using DC electricity. The integration of power sources such as photovoltaics and fuel cells, which produce DC power, offer further incentives to consider the use of DC systems. Using DC systems can help eliminate the conversion losses associated with rectifiers and inverters which would be part of the infrastructure if AC distribution was used. In the literature, the study of DC distribution has been limited to customized systems. The objective of this research is to analyze DC distribution when applied to systems based on standard IEEE test feeder systems. The IEEE 13 node test feeder and the IEEE 37 node test feeder will be used as the basis for the analysis. Issues such as associated costs, protection and integration of appliances will also be addressed.
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Halls, Daniel Charles. "Remote Electron Beam Induced Current (REBIC) and cathodoluminescence studies of some zinc oxide and varistor ceramics." Thesis, Imperial College London, 1998. http://hdl.handle.net/10044/1/8008.
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Jooste, Kritzman Phillip. "A load management system for fixed appliances in a safe DC RDP house." Thesis, Cape Peninsula University of Technology, 2017. http://hdl.handle.net/20.500.11838/2634.
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Thesis (MTech (Electrical Engineering))--Cape Peninsula University of Technology, 2017.This dissertation represents the design and development of a load management system for fixed appliances in a safe direct current (DC) Reconstruction and Development Programme (RDP) house. A combination of valley filling, load shifting and peak clipping load management techniques were employed to assist in reducing the peaks observed in the RDP house load profile during peak hours. A DC RDP house laboratory model was developed. The study is based on the assumption that the normally 220 V alternative current (AC) grid is replaced by a 350 V DC grid. The assumption is thus that 350 V DC is available at the distribution box in the RDP house laboratory model. All theoretical work was based on a 350 V DC system, but due to the lack of a laboratory 350 V DC supply, all physical tests were conducted by making use of a 300 V DC supply which was available. Consequently all calculations were thus based on 300 V DC as well. The geyser was the main fixed appliance focused on since it contributes to a significant portion of the power used. An AC geyser was successfully modified in order to be used in the DC network. Safety of the system was considered in order to interrupt the power in case of overcurrent or to isolate the power. Electronic switches were also developed and implemented to ensure that the DC power could be safely switched on and off and that the low power DC was isolated from the high power DC. LabVIEW allowed all other appliances in the DC RDP house to be virtually represented so that a holistic view of the power use of the house could be represented. This also allowed the system to be successfully simulated before any physical work was conducted. The load management system was successfully implemented by making use of power line communication. This proved to be a cost effective means to apply the load management algorithm. The algorithm consisted mainly of power on / off instructions that were executed during peak and off-peak times. It follows the normal use of timers used in the AC system to help reduce demand. It was found that the load management system successfully reduced the demand during peak hours without compromising the basic needs of the user. The power line communication modem proved to be very reliable in implementing the load management algorithm.
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Smith, Johan. "High voltage direct current strategy solving power delivery shortages to localized area of national grid." Thesis, Cape Peninsula University of Technology, 2009. http://hdl.handle.net/20.500.11838/1102.
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Thesis (MTech (Electrical Engineering))--Cape Peninsula University of Technology, 2009The industrial and population growth of a nation can cause power delivery problems to localized areas of a national grid through their increased demand for electrical energy. One reason for these power shortages is the insufficient current carrying capacity of existing high voltage alternating current, (HVAC), transmission lines supplying the area. High voltage direct current (HVDC) transmission lines are a possible solution as they provide better power delivery than HVAC lines. New or upgraded HVAC lines, or HVDC lines or combinations of HVAC and HVDC lines are possible solutions to improve power delivery. This research investigates the various line possibilities using theory. and cutting edge frequency and time domain software tools. The challenge is how to approach this problem. What methodology or structure should be used? Thus one of the contributions of this work is the development of a strategy (flow chart), for solving power delivery problems to localized areas of a national grid through individual or combinations (e.g. parallel operation) of HVAC and/or HVDC transmission lines. The main contribution is the evaluation of a HVDC system as a solution to overcoming power delivery shortages to a localized area of a national grid. Three different software packages (two industrial and one academic) namely, PSCAD/EMTDC (time domain), DlgSILENT PowerFactory (frequency domain) and MathCAD software are evaluated for their capability to perform the simulation studies necessary to prove the possible solutions given in the developed flow chart. The PSCAD/EMTDC software package is evaluated for integrated HVAC/HVDC load flow analyses, DlgSILENT for individual and parallel combinations of HVAC lines and MathCAD to prove hand calculations to software results. Five case studies are conducted. The first case study demonstrates a healthy system with no delivery shortcomings, the second case study portrays the delivery shortcoming due to increased localized area demand, and the remaining three case studies explore possible solutions to solve the problem. The first possible solution is to construct an identical HVAC line in parallel to the existing line.
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Taylor, Robert A. "Comprehensive optimization for thermoelectric refrigeration devices." Diss., Columbia, Mo. : University of Missouri-Columbia, 2005. http://hdl.handle.net/10355/4247.
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Thesis (M.S.)--University of Missouri-Columbia, 2005.The entire dissertation/thesis text is included in the research.pdf file; the official abstract appears in the short.pdf file (which also appears in the research.pdf); a non-technical general description, or public abstract, appears in the public.pdf file. Title from title screen of research.pdf file viewed on (December 20, 2006) Includes bibliographical references.
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Verga, Lucas Garcia [UNESP]. "Estudo dos efeitos do tamanho e comensurabilidade nas correntes críticas em fitas supercondutoras do tipo II com redes periódicas de pinnings à temperatura finita." Universidade Estadual Paulista (UNESP), 2015. http://hdl.handle.net/11449/126540.
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000841815.pdf: 3196563 bytes, checksum: 3523caeab4aa40cfcd97c06fb40cf134 (MD5)No trabalho de pesquisa dapresentado nesta dissertação, simulamos o comportamento dinâmico de vórtices magnéticos em fitas supercondutoras do tipo II. Consideramos tais fitas bidimensionais, com comprimento infinito, centro de pinnings distribuídos de maneira aleatória e com simetrias e Kagomé e submetidas a um campo magnético perpendicular ao seu plano. Os cálculos foram realizados para diversas larguras de fita, buscando estudar os efeitos de tamanhos nas propriedades dinâmicas dos vórtices. Nosso sistema foi descrito por um conjunto de equações de Langevin que foram resolvidas numericamente. Utilizando técnicas de dinâmica molecular obtivemos a evolução temporal das posições dos vórtices, o que nos permitiu analisar a média temporal das velocidades e da resistência diferencial em função da força de transporte aplicada. Para implementar os cálculos de dinâmica molecular, usamos o método de Simulated Annealing para encontrar os valores de campo magnético e as posições mais estáveis para cada densidade de vórtices considerada na simulação. Constatamos que, assim como em filmes infinitos, a rede hexagonal de pinnings apresentou valores de forças críticas superiores ao da distribuição aleatória de pinnings. Entretanto, para fitas supercondutoras, a diferença entre as duas redes é muito menor do que para sistemas infinitos, devido à perda de comensurabilidade da rede hexagonal causada pelos efeitos de tamanho. Em contrapartida, pequenas deformações geométricas na rede hexagonal de pinnings permitiram um maior grau de comensurabilidade, e consequentemente, um aumento drástico nas correntes críticas. Observamos que além dos efeitos de tamanho, os efeitos de pinnings também alteram a densidade de vórtices presente na fita supercondutora, influenciando diretamente nos efeitos de comensurabilidade e nos valores de forças críticas
No trabalho de pesquisa apresentado nesta disssertação, simulamos o comportamento dinâmico de vórtices magnéticos em fitas supercondutoras do tipo II. Consideramos tais fitas bidimensionais, com comprimento infinito, centros de pinnings distribuídos de maneira aleatória e com simetrais hexagonal e kagomé e submetidas a um campo magnético perpendicular ao seu plano. Os cálculos foram realizados para diversas larguras de fita, buscando estudar os efeitos de tamanhos nas propriedades dinâmicas dos vórtices. Nosso sistema foi descrito por um conjunto de equações de Langevin que foram resolvidas numericamente. Utilizando técnicas de dinâmica molecular obtivemos a evolução temporal das posições dos vórtices, o que nos permitiu analisar a média temporal das velocidades e da resistência diferencial em função da força de transporte aplicada. Para implementar os cálculos de dinâmica molecular, usamos o método de Simulated Annealing para encontrar os valores dos campos magnético e as posições mais estáveis para cada densidade de vórtices considerada na simulação. Constatamo que, assim como em filmes infinitos, a rede hexagonal de pinnings apresentou valores de forças críticas superiores ao da distribuição de pinnings. Entretanto, para fitas supercondutoras, a diferença entre as duas redes é muito menor do que para sistemas infinitos, devido à perda de comensurabilidade da rede hexagonal causada pelos efeitos de tamanho. Em contrapartida, pequenas deformações geométricas na rede hexagonal de pinnings permitiram um maior grau de comensurabilidade, e consequentemente, um aumento drástico nas correntes críticas. Observamos que além dos efeitos de tamanho, os efeitos de pinnings também alteram a densidade de vórtices presente na fita supercondutora, influenciando diretamente nos efeitos de comensurabilidade e nos valores de forças críticas
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Verga, Lucas Garcia. "Estudo dos efeitos do tamanho e comensurabilidade nas correntes críticas em fitas supercondutoras do tipo II com redes periódicas de pinnings à temperatura finita /." Bauru, 2015. http://hdl.handle.net/11449/126540.
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Orientador: Pablo Antonio Venegas UrendaBanca: André Luiz Malvezzi
Banca: Rafael Zadorosny
O Programa de Pós Graduação em Ciência e Tecnologia de Materiais, PosMat, tem caráter instituciona e integra as atividades de pesquisa em materiais de diversos campi
Resumo: No trabalho de pesquisa dapresentado nesta dissertação, simulamos o comportamento dinâmico de vórtices magnéticos em fitas supercondutoras do tipo II. Consideramos tais fitas bidimensionais, com comprimento infinito, centro de pinnings distribuídos de maneira aleatória e com simetrias e Kagomé e submetidas a um campo magnético perpendicular ao seu plano. Os cálculos foram realizados para diversas larguras de fita, buscando estudar os efeitos de tamanhos nas propriedades dinâmicas dos vórtices. Nosso sistema foi descrito por um conjunto de equações de Langevin que foram resolvidas numericamente. Utilizando técnicas de dinâmica molecular obtivemos a evolução temporal das posições dos vórtices, o que nos permitiu analisar a média temporal das velocidades e da resistência diferencial em função da força de transporte aplicada. Para implementar os cálculos de dinâmica molecular, usamos o método de Simulated Annealing para encontrar os valores de campo magnético e as posições mais estáveis para cada densidade de vórtices considerada na simulação. Constatamos que, assim como em filmes infinitos, a rede hexagonal de pinnings apresentou valores de forças críticas superiores ao da distribuição aleatória de pinnings. Entretanto, para fitas supercondutoras, a diferença entre as duas redes é muito menor do que para sistemas infinitos, devido à perda de comensurabilidade da rede hexagonal causada pelos efeitos de tamanho. Em contrapartida, pequenas deformações geométricas na rede hexagonal de pinnings permitiram um maior grau de comensurabilidade, e consequentemente, um aumento drástico nas correntes críticas. Observamos que além dos efeitos de tamanho, os efeitos de pinnings também alteram a densidade de vórtices presente na fita supercondutora, influenciando diretamente nos efeitos de comensurabilidade e nos valores de forças críticas
Abstract: No trabalho de pesquisa apresentado nesta disssertação, simulamos o comportamento dinâmico de vórtices magnéticos em fitas supercondutoras do tipo II. Consideramos tais fitas bidimensionais, com comprimento infinito, centros de pinnings distribuídos de maneira aleatória e com simetrais hexagonal e kagomé e submetidas a um campo magnético perpendicular ao seu plano. Os cálculos foram realizados para diversas larguras de fita, buscando estudar os efeitos de tamanhos nas propriedades dinâmicas dos vórtices. Nosso sistema foi descrito por um conjunto de equações de Langevin que foram resolvidas numericamente. Utilizando técnicas de dinâmica molecular obtivemos a evolução temporal das posições dos vórtices, o que nos permitiu analisar a média temporal das velocidades e da resistência diferencial em função da força de transporte aplicada. Para implementar os cálculos de dinâmica molecular, usamos o método de Simulated Annealing para encontrar os valores dos campos magnético e as posições mais estáveis para cada densidade de vórtices considerada na simulação. Constatamo que, assim como em filmes infinitos, a rede hexagonal de pinnings apresentou valores de forças críticas superiores ao da distribuição de pinnings. Entretanto, para fitas supercondutoras, a diferença entre as duas redes é muito menor do que para sistemas infinitos, devido à perda de comensurabilidade da rede hexagonal causada pelos efeitos de tamanho. Em contrapartida, pequenas deformações geométricas na rede hexagonal de pinnings permitiram um maior grau de comensurabilidade, e consequentemente, um aumento drástico nas correntes críticas. Observamos que além dos efeitos de tamanho, os efeitos de pinnings também alteram a densidade de vórtices presente na fita supercondutora, influenciando diretamente nos efeitos de comensurabilidade e nos valores de forças críticas
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