Dissertations / Theses: 'Electric current'

1

Lee, Hyunwoo. "Electric current fluctuations in mesoscopic systems." Thesis, Massachusetts Institute of Technology, 1996. http://hdl.handle.net/1721.1/38380.

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Saunders, Theo Graves. "Effect of electric current on ceramic processing." Thesis, Queen Mary, University of London, 2017. http://qmro.qmul.ac.uk/xmlui/handle/123456789/25943.

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This work was on the effect of electric current on the processing of ceramics. The focus was on electromigration/electrochemistry and plasma effects. While there is no solid evidence that there is plasma in Spark Plasma Sintering, (SPS), newer techniques e.g. flash, use different conditions so there is an interest in understanding the conditions under which a plasma forms. The minimum arcing voltage was found from literature to be from 10-15V for materials of interest. This is above that found in SPS (10V). However, due to the many contact points in a powder compact much higher voltages (50V) were required in practical experiments. Optical spectroscopy was used to verify the formation of a plasma, and emission peaks from the powder compact material were visible implying they were vaporised and formed the plasma. Electromigration was exploited to alter the oxidation of zirconium diboride, by passing current through the oxide layer (120μm zirconia base grown at 1200°C) oxygen could be pumped either away or toward the diboride bulk. Small cubes (3mm) of diboride had platinum foil electrodes applied on both sides and oxidation was performed at 1400°C for 5hr. Without a field the oxide grew to 360μm, by applying 10V and 100mA the oxide grew to 150μm under the +ve electrode but 1400μm under the -ve electrode. Electrochemical reduction was believed to have occurred due to the electrical properties of the material changing during oxidation and visible blackening of the oxide. Combining the techniques from both earlier works, a contactless flash sintering setup was developed. This used two plasma arcs as electrodes to heat and pass current through the sample. Various materials, currents and times were used, but the best result was with SiC:B4C which was sintered in 3s with 6A, the microstructure showed sharp grains, no segregation and limited grain growth ( initially 0.7μm SiC and 0.5μm B4C, this grew to 1.1μm and 1.4μm). This was the first recorded case of contactless flash sintering and the technique has the potential to sinter ceramics in a continuous manner.

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Ho, Kwun-yuan Godwin, and 賀觀元. "A novel integrated synchronous rectifier for LLC resonant converter." Thesis, The University of Hong Kong (Pokfulam, Hong Kong), 2012. http://hub.hku.hk/bib/B49618180.

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There is ever-increasing demand in telecommunication system, data server and computer equipment for low voltage, high current power supply. LLC resonant converter is a good topology on primary side of the converter because it has soft switching and resonant conversion. However, the passive rectifier in the secondary side has high power dissipation. Synchronous rectifier is a popular method to reduce this rectification loss. Although there are many types of synchronous rectifier for PWM converter, most of them do not function well in LLC resonant converters. It is because the wave form of LLC resonant converter is different from PWM. The objective of this research is to reduce the power dissipation and physical size at the same time. In this thesis, a novel current driven synchronous rectifier with saturable current transformer and dynamic gate voltage control for LLC resonant Converter is presented. This novel circuit reduces the rectification loss and size of the current transformer in the synchronous rectifier. This synchronous rectifier has several outstanding characteristics compared with generic voltage driven and current driven synchronous rectifier. The saturable feature reduces the current transformer turns. Inherent dynamic gate voltage controlled by saturable current transformer reduces gate loss in the MOSFET. A novel driving circuit is proposed for accurate turn off time. It reduces loss significantly. This synchronous rectifier is completely self-contained which can replace the rectifier diode as a drop in replacement. It is insensitive to parasitic inductance. In order to explain the current transformer saturable, a model of saturable current transformer is proposed. A prototype demonstrates the advantages of the proposed current driven synchronous rectifier. Furthermore, a novel integrated synchronous rectifier is presented which provides a more compact system. The synchronous rectifier current transformer is integrated with the main transformer which reduces the number of circuit joints in power path. Each soldering joint generates significance loss in power converter. A pair of 0.5mΩ soldering joint in 25A current path produces 0.62W loss. The placement of the integrated current transformer is important. A criterion for the placement of the current transformer within the main transformer is to avoid interference to the current transformer from the magnetic flux of the main transformer. Thus, a placement method to integrate the current transformer into the main transformer is proposed. An integrated current transformer model is suggested to explain the operation of the integrated synchronous rectifier. A prototype demonstrates the advantages of the integrated synchronous rectifier. published_or_final_version Electrical and Electronic Engineering Master Master of Philosophy

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White, Terence H. "A three-phase hybrid dc-ac inverter system utilizing hysteresis control." Thesis, Monterey, Calif. : Springfield, Va. : Naval Postgraduate School ; Available from National Technical Information Service, 2004. http://library.nps.navy.mil/uhtbin/hyperion/04Jun%5FWhite%5FTerence.pdf.

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Williams, Mark Richard. "A controlled current inverter for an electric vehicle." Thesis, University of Canterbury. Department of Electrical and Electronic Engineering, 1993. http://hdl.handle.net/10092/2280.

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The University of 'Canterbury Mark II' electric vehicle has been out of service for several years due to the lack of a suitable inverter to provide a variable frequency AC supply to its traction motors. This thesis describes the design and construction of such an inverter, using high current bipolar junction transistors as the switching elements, so that the car might be returned to service in the near future. The inverter is based on an existing commercial AC motor speed controller. Modifications to this AC motor speed controller were made to suit the low voltage, high current rating of the traction motors. These modifications are described and it is shown that these modifications permitted the inverter to deliver the required increase in current. The inverter differs from most conventional AC motor speed controllers in that it acts to shape load current rather than potential, and uses an asynchronous switching technique to do this. The Thesis describes this technique and the control hardware constructed to implement it. Test results, showing the performance of the combined inverter/motor system are then presented graphically and discussed with reference to standard AC motor theory, giving consideration to the harmonic content of the AC waveforms. Consideration is also given to a suitable closed-loop control system which could be expected to ensure that the inverter's output frequency is controlled in such a manner as to give a safe and predictable response to the brake and accelerator controls.

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Rincon-Mora, Gabriel Alfonso. "Current efficient, low voltage, low drop-out regulators." Diss., Georgia Institute of Technology, 1996. http://hdl.handle.net/1853/13359.

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Dixon, Juan W. (Juan Walterio). "A DC voltage regulated, controlled current PWM rectifier /." Thesis, McGill University, 1986. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=65923.

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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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Xu, Kemu. "Simulation of Electrical Characteristics in Oxyfuel Flame Subject to An Electric Field." Thesis, Virginia Tech, 2021. http://hdl.handle.net/10919/103816.

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The oxyfuel cutting method is still widely used nowadays, even though it is not a fully autonomous process. Thisthesis presents a computational model to study ion and electron transport and current-voltage characteristics inside a methane-oxygen flame. By finding the relationship between current-voltage characteristics and critical parameters,such as standoff, fuel oxygen ratio, and flow rate, a control algorithm could be implemented into the system and make it autonomous. Star CCM+ software is used to develop preheat phase computational models by splitting the simulations into the combustion and electrochemical transport parts. Both the laminar and turbulent flows are considered. Several laboratory experiments are used to compare test data with the numerical results generated using this model. The initial and boundary conditions used in the simulation were to the extent possible similar to the experimental conditions in the laboratory experiment. In the combustion part, the general GRI3.0 mechanism plus three additional ionization reactions are applied, and the combustion part results are then used as input into the electrochemical transport part. A particular inspection line inside the domain is created to analyze the results of the electrochemical transport part. Ions, electrons number density, and current density are studied in the interval from -40V to 40V electric potential. The ions are heavier and more challenging to move than electrons. The results show that at both the torch and work surfaces, charged sheaths are formed, which cause three different regions of current-voltage relations to form in a similar manner as observed in the tests. Master of Science Oxyfuel cutting is essential to numerous industries, such as shipbuilding, rail, earth moving equipment, commercial building construction, etc. Tuning the process parameters and diagnosing problems with the oxyfuel process still relies on experienced operators. The main obstacles to the automation of the oxyfuel process come from the limitations of the sensing suites currently in use. Since typical sensors are highly unreliable in the harsh environment near the high-temperature flame, an alternate method is proposed to find the co-dependence between the flame's electrical characteristics and critical parameters of the oxyfuel cutting system (standoff, flow rate, F/O ratio, etc.). The relevant electrical characteristics are the electrical potential and distribution of ions and electrons. Two-dimensional models are created to analyze the combustion of methane-oxygen flame and transport of ions and electrons. The models allow the derivation of the current-voltage characteristic between the torch and work surface. Also, the way sheath phenomena of ions and electrons on the surface affect the current-voltage relationship can be analyzed from ions and electrons distribution. The electric field is added to the model by applying a constant voltage to the torch tip surface. To validate the models, a laboratory experiment with a similar geometry arrangement is used as a comparision. The models' results reveal three different regimes in the current-voltage relationship.

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Stihi, Omar. "Single phase controlled current PWM converter." Thesis, McGill University, 1987. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=63844.

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Cully, C. M. "Electric fields and current sheet structure in magnetospheric plasmas." Connect to online resource, 2007. http://gateway.proquest.com/openurl?url_ver=Z39.88-2004&rft_val_fmt=info:ofi/fmt:kev:mtx:dissertation&res_dat=xri:pqdiss&rft_dat=xri:pqdiss:3273738.

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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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Chu, Beatrice C. B. "Novel optical methods for flowmetering and electric current sensing." Thesis, University of Kent, 1992. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.314488.

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Corne, Adrien. "Current Sensorless Control Strategies for an Automotive Electric Powertrain." Electronic Thesis or Diss., Université de Lorraine, 2019. http://www.theses.fr/2019LORR0292.

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L’application de quotas d’émissions de gaz à effet de serre a amené les constructeurs automobiles à augmenter le niveau d’électrification de leurs véhicules. En parallèle des véhicules tout électrique, se sont développées les solutions hybrides, tel le mild-hybrid autorisant l’association d’une chaîne de traction électrique avec le moteur à combustion dans le but d’absorber les pics de consommation de carburant. Afin de rester compétitif, les coûts de production d’un véhicule doivent être optimisés autant que possible, ainsi l’étude réalisée de commande de machine synchrone à griffes sans capteur de courant permet la suppression des capteurs du stator de la machine et donc de s’affranchir de leur coût. Une commande vectorielle de la machine est nécessaire afin d’optimiser les courants statoriques pour un couple donné. L’utilisation d’observateurs d’état permettant l’estimation des courants manquants a donc été privilégiée. Ainsi différentes topologies d’observateurs ont été développées : le filtre de Kalman étendu ainsi qu’un observateur d’état et deux déclinaisons dont la conception est basée sur une analyse de convergence à l'aide de fonctions de Lyapunov. Afin d’améliorer la précision de l’observation des courants statoriques, une étude approfondie du modèle électrique de la machine a été réalisée. Elle permet de minimiser les erreurs dues aux variations paramétriques, liées notamment à la saturation magnétique de la machine et des incertitudes liées aux phénomènes non modélisés de la chaîne de conversion électromécanique. Une méthode de cartographie de la machine a ainsi été proposée à l’aide d’un estimateur paramétrique. Les résultats expérimentaux, obtenus sur un banc de test réalisé en laboratoire, sont concluants en régime établi : les courants non mesurés sont estimés avec une précision satisfaisante pour une application automobile et permettent le contrôle sans capteur de courant de la machine The application of greenhouse gases quotas has led the automotive manufacturers to increase the electrification level of their vehicles. In parallel with Battery Electric Vehicles (BEV), hybridization solutions have been developed. Among them, mild-hybrid technology allows the connection of an electric powertrain with an Internal Combustion Engine (ICE) with the aim of absorbing peaks of fuel consumption. In order to remain competitive, the manufacturing costs of a vehicle need to be optimized. In that regard, removing the stator currents sensors allows avoiding their inherent costs. However, within the vector control framework, a feedback on these currents is required to optimize their value for a given torque. For this reason, it has been decided to use state observers to estimate the missing currents. Different state observer solutions have thus been developed: the Extended Kalman Filter (EKF) and a state observer with two extensions whose design is based on a convergence analysis using Lyapunov functions. With the aim of improving the precision of the stator currents estimation, an in-depth study of the machine's electrical model was carried out. It allows minimizing errors due to parametric variations, related in particular to the magnetic saturation of the machine and uncertainties due to unmodeled phenomena in the whole drive. A method for mapping the machine was proposed using a parametric estimator. The experimental results, obtained on a test bench built in the laboratory, are conclusive in steady-state: the real currents are estimated with a satisfying precision for an automotive application and allow performing a current sensorless control of the machine

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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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Hall, David Eric. "Transient thermal models for overhead current-carrying hardware." Thesis, Georgia Institute of Technology, 1993. http://hdl.handle.net/1853/17133.

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17

Sellars, Malcolm. "Electric field mill for the simultaneous measurement of electric field strength and ion current diensity." Master's thesis, University of Cape Town, 1995. http://hdl.handle.net/11427/22039.

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In the last 20 years, the use of high voltage direct current (HVDC) power transmission has grown considerably. With the increase in the number of HVDC transmission lines and in the transmission voltages, concern has increased as to possible health effects. For research on these health effects to be carried out, it is necessary to measure the electrical environment ofHVDC transmission lines accurately. The electrical environment ofHVDC transmission lines is characterised by: Electric field strength E [Vim];Ion current density J [A/m²] ;Space charge density p [C/m³ ]. Typical values measured under HVDC transmission lines are: E = lOkV/m, J = 400nA/m² . This thesis describes the design, construction and testing of an electric field mill capable of measuring electric field strength from 0 to 25kV/m (resolution = lOV/m), and ion current density from 0 to 1000 nA/m² (resolution = 20nA/m² ). The electric field readings have an accuracy of ±8%. The ion current density readings have an accuracy of ±12%. The field mill was tested in the laboratory in a simulated HVDC environment, and found to give good performance. For operation under a HVDC line, the field mill design will need some alterations to make it weatherproof. The design considerations described in this thesis should be helpful in the design of electric field mills in general.

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Nishimoto, Masahiro. "Analytical study of a controlled current PWM converter." Thesis, McGill University, 1986. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=65432.

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19

Siebrits, F. B. (Francois Bart). "Field implementation of a transient voltage measurement facility using HV current transformers." Thesis, Stellenbosch : Stellenbosch University, 2003. http://hdl.handle.net/10019.1/53426.

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Thesis (MScEng)--University of Stellenbosch, 2003. ENGLISH ABSTRACT: The bandwidth of standard HV measurement devices such as capacitive voltage transformers is too limited in order to measure wideband phenomena. This thesis is concerned with the investigation into a non- intrusive HV transient voltage measurement facility using standard substation HV current transformers (CI's) configured in a transconductance topology. The sensing, summation and integration of the CT capacitive earth currents are investigated. This thesis also reports on the development of a optically isolated link using optical fibre for signal transfer and a computer based data acquisition system. AFRIKAANSE OPSOMMING: Standaard hoogspannings (HS) meettoerusting soos kapasitiewe spannmgs transformators het beperkte bandwydte vir die meet van wyeband verskynsels. Hierdie tesis handel oor die implementering van 'n HS meetstelsel wat op meinbrekende wyse oorgangsverskynsels meet deur middel van HS stroomtransformators wat in 'n transkonduktansie topologie gekonfigureer is. Die meet, sommasie en integrasie van kapasitoewe grondstrome word ondersoek. Hierdie tesis doen ook verslag aangaande die ontwikkeling van 'n optiese geisoleerde koppelvlak wat gebruik word vir seinoordrag en 'n rekenaar gebasseerde data versamelaar. pdv201406

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Ridley, Raymond B. "A new small-signal model for current-mode control." Diss., This resource online, 1990. http://scholar.lib.vt.edu/theses/available/etd-07282008-135124/.

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吳熾華 and Che-wa Ng. "An advanced ac drive system for an electric van." Thesis, The University of Hong Kong (Pokfulam, Hong Kong), 1990. http://hub.hku.hk/bib/B31231937.

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Ng, Che-wa. "An advanced ac drive system for an electric van /." [Hong Kong : University of Hong Kong], 1990. http://sunzi.lib.hku.hk/hkuto/record.jsp?B12691276.

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23

Tang, Wei. "Average current-mode control and charge control for PWM converters." Diss., This resource online, 1994. http://scholar.lib.vt.edu/theses/available/etd-03042009-041130/.

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24

Nielsen, Torbjörn. "Electric arc-contact interaction in high current gasblast circuit breakers." Licentiate thesis, KTH, Mechanics, 2001. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-1275.

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Cai, Xiaopeng. "Electric Current Induced Stresses Around the Crack Tip in Conductors." NCSU, 1997. http://www.lib.ncsu.edu/theses/available/etd-19970508-092022.

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Electric current can have a variety of effects on the mechanical behavior of conductors, especially when flaws are present in the materials. Two of the effects, namely the magnetic effect and the thermal effect, on the stress distribution around a crack tip in a conducting material have been investigated. The conductor is assumed to be linearly elastic with constant values of mechanical and physical properties. However, the stresses is proportional to the square of the current in some cases, according to Lorentz's law and Joule's law. Static analysis as well as dynamic analysis are carried out to reveal the effects of the electric current on the stress distribution around the crack tip.General solutions are derived for the static analyses of the thermal effect and the magnetic effect caused by an externally applied magnetic field. Analytical analyses are carried out to reveal the characteristics of stress distribution around the crack tip for these two cases. For the static analysis of magnetic effect caused by the self-induced magnetic field, a numerical analysis procedure is developed. Similar numerical procedures are also developed to analyze the effects of the electric current, both thermal and magnetic, under dynamic conditions.Although the electric current is singular around the crack tip, the analysis results reveal that, under static conditions, the stresses caused by the electric current around the crack tip remain the original singular order of -1/2. Under dynamic conditions, however, the stress distribution does not have a consistent singular order due to the complicated temperature distribution. It is concluded that the fracture criteria based on the stress intensity factors may not be applicable because of the complicated stress distribution. A criterion in terms of critical stress at a critical distance ahead of the crack tip is used in an attempt to correlate analysis results with some existing experimental observations. The major trends are consistent between the analysis results and the experimental observations. By utilizing the analysis results, the electric current could be used to actively control the damage propagation in conductors, hence catastrophic failure could be avoided.

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Yakum, Charles Nchonko. "Electric current measurement in power systems using optical fibre techniques." Thesis, University of Liverpool, 1996. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.387450.

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Karlsson, Erika, Martin Koch, and Sissel Wangenborg. "Electric vehicle charging infrastructure in Uppsala : Current state and potential." Thesis, Uppsala universitet, Institutionen för teknikvetenskaper, 2016. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-295031.

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The aim of this study is to make an inventory of the charging infrastructure for electric vehicles in Uppsala municipality. The 89 public charging outlets in the area has been compiled according to their outlet type and power output and located in a map. The charging stations are deployed in the centre of Uppsala and in the outskirts, mainly the eastern parts. The total installed power of the charging outlets in Uppsala is 1036 kW. Potential energy use of the charging outlets has been calculated with several different coverage ratios. The result of potential energy use in a year with 100% coverage ratio is approximately 9 GWh which as an example equals 70% of Ångström Laboratory's electric energy use or 0.6% of Uppsala municipality's over a year. With data from 16 specific charging stations in Uppsala and other cities, coverage estimates have been done with a result between less than 1% up to 13%. It is concluded in this study that further measurements of the charging outlets' electric energy consumption are necessary in order to calculate coverage ratios and coordinate an expansion of the charging infrastructure.

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Stone, Katherine M. "Effects of an electric current applied to metals during solidification." Thesis, Massachusetts Institute of Technology, 2019. https://hdl.handle.net/1721.1/122446.

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Thesis: S.M., Massachusetts Institute of Technology, Department of Materials Science and Engineering, 2019 "June 2019." Cataloged from PDF version of thesis. Includes bibliographical references (pages 31-34). Solidification is an important, yet not fully understood, materials process. One way to better understand solidification, or at least to better control it, is through applying outside effects onto the solidifying material. Private industrial experiments performed by Dr. Eric Dahlgren suggested that there might be a trend of increased undercooling in a metallic sample as more current was applied. An expansion of those experiments was commenced to A) confirm this trend and B) explore its potential causes, with the ultimate goal of being able to reliably change undercooling in a metallic material to affect its final properties. An experiment was designed where gallium could be subjected to between o and 20 amps of applied direct current. The gallium sample could then be cooled, while its thermal history over time could be recorded. The cooling curves of the gallium between melting and recalescence points were then used to try and quantify the effect of the applied current. It was shown that increasing the applied current did increase the undercooling time, specifically the time to homogenous nucleation. Although no mechanism to explain this phenomenon has been conclusively proved, this project was able to help reduce the likelihood of several theories. Simple calculations showed that joule heating does not create enough heat flux to change the temperature and effect the formation of nuclei in the melt. Experimental results showed that the observed phenomenon was due to the effects on a nucleation-based process, not a growth process, disproving several growth-based theories for this phenomenon. Additionally, certain common assumptions in previous experiments about the effects of a magnetic field, or of joule heating, were disproven. These advances, and some of the setbacks experienced in this project, lay a path for improvements in future work that may find the precise cause of this effect. by Katherine M. Stone. S.M. S.M. Massachusetts Institute of Technology, Department of Materials Science and Engineering

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Wang, Zheng, and 王政. "Chaoization and stabilization of electric motor drives and their industrial applications." Thesis, The University of Hong Kong (Pokfulam, Hong Kong), 2008. http://hub.hku.hk/bib/B40687594.

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Wang, Zheng. "Chaoization and stabilization of electric motor drives and their industrial applications." Click to view the E-thesis via HKUTO, 2008. http://sunzi.lib.hku.hk/hkuto/record/B40687594.

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Kvalheim, Erik M. "Comparison of input current spectral components for flyback PWM and resonant converters." Thesis, This resource online, 1991. http://scholar.lib.vt.edu/theses/available/etd-11072008-063706/.

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Gummi, Karteek. "Derivation of new double-input DC-DC converters using the building block methodology." Diss., Rolla, Mo. : Missouri University of Science and Technology, 2008. http://scholarsmine.mst.edu/thesis/pdf/Gummi_09007dcc804fa7b9.pdf.

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Thesis (M.S.)--Missouri University of Science and Technology, 2008. Vita. The entire thesis text is included in file. Title from title screen of thesis/dissertation PDF file (viewed May 12, 2008) Includes bibliographical references (p. 102-107).

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Tsang, D. M. C. "Improvements in integrated high-quality rectifier-regulators." Thesis, Virginia Tech, 1993. http://hdl.handle.net/10919/41945.

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Crowe, Robert A. "Design, construction and testing of a reduced-scale cascaded multi-level converter." Thesis, Monterey, Calif. : Springfield, Va. : Naval Postgraduate School ; Available from National Technical Information Service, 2003. http://library.nps.navy.mil/uhtbin/hyperion-image/03Jun%5FCrowe.pdf.

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Thesis (M.S. in Electrical Engineering)--Naval Postgraduate School, June 2003. Thesis advisor(s): Robert W. Ashton, John G. Ciezki, Douglas J. Fouts. Includes bibliographical references (p. 125-126). Also available online.

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Gatarić, Slobodan. "Single-switch three-phase zero-current-transition rectifier with power factor correction /." This resource online, 1994. http://scholar.lib.vt.edu/theses/available/etd-12162009-020342/.

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Ai, Yong-le. "Novel direct field and torque control of six-phase induction machine with special phase current waveform." Thesis, Link to the online version, 2006. http://hdl.handle.net/10019/489.

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Gous, Marthinus Gerhardus Faculin. "Shunt active power filtering algorithms for unbalanced, non-linear loads." Thesis, Stellenbosch : Stellenbosch University, 2003. http://hdl.handle.net/10019.1/53589.

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Thesis (MScEng)--University of Stellenbosch, 2003. ENGLISH ABSTRACT: This thesis presents the design and implementation of shunt active power filtering algorithms for unbalanced, non-linear loads. A three-phase four-wire topology is developed in the dqO space. Based on this development an accurate dynamic system model, taking into account the effect of the neutral inductor is developed. The synchronous reference frame technique is expanded to enable the isolation of the zero sequence current component into its instantaneous active and reactive current components. Additionally a prediction method is proposed that will enable the proper prediction of the reference currents in a threephase four-wire system. Two categories of reference current signal tracking algorithms are investigated; namely the predictive current controller and the sliding mode current controller. A compensating technique is proposed to compensate for the effects that sampling and computational time delay have on the performance of the system. Additionally, an investigation is done into the effect that dead-time has on the performance of the system, and based on this investigation a dead-time compensating strategy is proposed. Finally simulation and practical results are provided to validate the discussed theories. AFRIKAANSE OPSOMMING: Hierdie verhandeling ondersoek die ontwerp en implementering van parralel gekoppelde aktiewe filter algoritmes vir ongebalenseerde, nie-lineêre laste. 'n Drie-fase vier-draad topologie, asook 'n korrekte model van die dinamiese sisteem, wat die effek van die neutraal induktor insluit, is ontwikkel in die dqO ruimte. Die sinchroon verwysing vlak tegniek is uitgebrei om die isolering van die nul sekwensie stroom in onderskeidelik die oombliklike aktiewe en reaktiewe stroom komponente te verdeel. Addisioneel is a vooruitskatting tegniek aanbeveel wat die beheerder in staat sal stelom voldoende die verwysing strome vooruit te skat in 'n drie-fase vier-draad stelsel. Twee katagoriee van verwysing stroom volging algoritmes is ondersoek, naamlik die afskatting stroom beheerder en die gleiende modus stroom beheerder. 'n Effektiewe kompensasie tegniek is voorgestel om die effek van tydvertraging as gevolg van monstering en verwerking te elimineer. Addisioneel is die effek van dooie-tyd ondersoek en gebasseer op hierdie ondersoek is 'n effektiewe dooie-tyd kompensasie tegniek voorgestel. Laastens is simulasies en praktiese resultate verskaf om die werking van die voorgestelde teorie te bevestig.

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Kulkarni, Ashok. "Characteristics of a controlled current PWM converter." Thesis, McGill University, 1986. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=66006.

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Yeh, Thomas. "Analysis of power factor correction converters /." Online version of thesis, 1992. http://hdl.handle.net/1850/11220.

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Chen, Qing. "Analysis and design of multiple-output forward converter with weighted voltage control /." This resource online, 1994. http://scholar.lib.vt.edu/theses/available/etd-10032007-171757/.

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Miller, Douglas P. "Introduction of a current waveform, waveshaping technique to limit conduction loss in high-frequency dc-dc converters suitable for space power." Thesis, Monterey, California : Naval Postgraduate School, 1990. http://handle.dtic.mil/100.2/ADA237903.

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Thesis (M.S. in Electrical Engineering)--Naval Postgraduate School, June 1990. Thesis Advisor(s): Ewing, Gerald D. Second Reader: Michael, Sherif. "June 1990." DTIC Indentifier(s): Dc to dc converters, waveform generators, program listings, theses. Author(s) subject terms: dc-dc converter, quasi-resonant, Buck converter. Includes bibliographical references (p. 142-145). Also available in print.

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Ho, Wing-choi. "Loss analysis and design of a novel soft switching converter /." Hong Kong : University of Hong Kong, 1997. http://sunzi.lib.hku.hk/hkuto/record.jsp?B18865501.

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Li, Qiang. "A single-phase dual output converter with high quality input waveforms." Lexington, Ky. : [University of Kentucky Libraries], 2003. http://lib.uky.edu/ETD/ukyelen2003t00111/thesislq.pdf.

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Thesis (M.S.)--University of Kentucky, 2003. Title from document title page (viewed Sept. 10, 2004). Document formatted into pages; contains xi, 128 p. : ill. Includes abstract and vita. Includes bibliographical references (p. 127-128).

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Otto, Abraham Johannes. "Direct current conductor corona modelling and metrology." Thesis, Stellenbosch : University of Stellenbosch, 2009. http://hdl.handle.net/10019.1/1497.

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Thesis (PhD (Electrical and Electronic Engineering))--University of Stellenbosch, 2009. ENGLISH ABSTRACT: Prospects of up-rating existing high voltage direct current (HVDC) transmission schemes, as well as the conversion of existing alternating current (AC) to direct current (DC) lines and the development of new HVDC schemes in sub-Saharan Africa, have led to renewed interest in DC research. The radio interference (RI), audible noise (AN) and corona loss (CL) performance of HVDC transmission lines are critical factors when assessing the reliability of the line design. The RI performance is especially important when considering the successful transmission of the carrier signal of the power line carrier (PLC) system. The PLC system is the main form of communication between teleprotection devices on the Cahora Bassa HVDC scheme. The aim of the dissertation is to devise modelling as well as metrological techniques to characterise DC conductor corona. A particle-in-cell (PIC) computational code is developed to gain a better understanding of the physical processes that occur during corona events. The numerical code makes use of the charge simulation method (CSM) and nite element method (FEM) to solve for the Laplace and Poisson eld equations. Higher-order basis functions are implemented to obtain a more accurate solution to the Poisson equation. The computational tool yields insight into the mathematical models for the various ionization, attachment and electron avalanche processes that give rise to corona currents. Together with a designed and developed electrometer-type circuit, the numerical code assists the visualisation of the space charge particle dynamics that form in the electrode gap during corona events. The metrological techniques consider the wideband time domain (TD) as well as the frequency domain (FD) information of the measured corona pulses in the presence of noise. These are then compared to the narrowband CISPR standard measurements centred around 500kHz. The importance of impedance matching when attempting to derive a wideband excitation function is investigated. The TD measurements are quite distinct from the well-published FD measurements, and consider the pulse shape, pulse spectrum and pulse repetition rates. The use of three possible conductor corona test methods to study direct current conductor RI performance under both positive and negative polarities is investigated at high altitude in this dissertation. These include a small corona cage, a short test line and the Eskom Megawatt Park large outdoor corona cage. Derived wideband and narrowband monopolar DC RI excitation functions at 500kHz are consolidated with existing radio noise (RN) measurement protocols and prediction methods. The use of a corona cage to derive excitation functions for monopolar RI predictions is explored and it is shown that a small corona cage, due to the build-up of space charge in the small distance between the electrodes, cannot be used to predict the RI levels on HVDC transmission lines accurately. As a consequence of the physics, computational modelling and both frequency and time domain measurements, it is now possible to explain why a small cage system prevents the accurate RI prediction on transmission lines. The large outdoor corona cage and short test line RI performance predictions agree with existing empirical prediction formulas. AFRIKAANSE OPSOMMING: Vooruitsigte van die opgradering van bestaande hoogspanningsgelykstroom transmissielyn skemas, asook die omkering van bestaande wisselstroom na gelykstroom lyne en die ontwikkeling van nuwe hoogspanningsgelykstroom skemas in sub-Sahara Afrika, het gelei to hernude belangstelling in gelykstroomnavorsing. Die korona-werkverrigting van hoogspanningsgelykstroom oorshoofselyne in terme van radiosteuring, hoorbare-geraas en koronaverliese is kritiese faktore om in aanmerking te neem wanneer die betroubaarheid van die lynontwerp geëvalueer word. Die radiosteuring-werkverrigting is veral van belang tot die suksesvolle oordrag van die kraglyndragolf draersein wat die hoof kommunikasievorm tussen beskermingstoerusting op die Cahora Bassa transmissielyn skema is. Die doel van hierdie proefskrif is om modellering- sowel as meettegnieke te ontwerp om gelykstroomgeleierkorona te karakteriseer. 'n Partikel-in-sel numeriese kode is ontwikkel om 'n beter begrip te verkry van die siese prosesse gedurende koronagebeure. Die numeriese kode maak gebruik van die lading-simulasiemetode, sowel as die eindige element metode om die Laplace en Poisson veldvergelykings op te los. Hoër-orde basisfunksies is geimplimenteer om 'n meer akkurate oplossing vir die Poisson vergelyking te verkry. Die numeriese kode bied insig tot die wiskundige modelle vir die verskeie ionisasie-, aanhegtings- en lawineprosesse wat lei tot koronastrome in die area om die hoogspanningsgeleier. Die numeriese kode, saam met 'n elektro-meter wat ontwerp en ontwikkel is, dra by tot die begrip van die ruimtelading partikeldinamika wat onstaan in die elektrodegaping gedurende koronagebeure. Die meettegnieke neem die wyeband tydgebied- en frekwensiegebiedinformasie van die koronapulse in ag in die teenwoordigheid van geraas. Dit word dan vergelyk met die nouband CISPR meetstandaard vir 'n frekwensie van 500kHz. Die belangrikheid van impedansie-aanpassing vir wyeband metings met die doel om opwekkingsfunksies af te lei, word ondersoek. Die tydgebiedmetings verskil van die algemene frekwensiegebiedmetings, en ondersoek die pulsvorm, -spektrum en -herhalingskoers. Die gebruik van drie moontlike koronageleier-toetsmetodes om gelykstroom radiosteurings-werkverrigting vir positiewe en negatiewe polariteite te bestudeer by hoë vlakke bo seespieël word ondersoek in die proefskrif. Dit sluit in 'n klein koronakou, 'n kort toetslyn en die Eskom Megawatt Park groot buitelug-koronakou. Afgeleide wye- en nouband monopolêre gelykstroom radiosteuring opwekkingsfunksies by 500kHz word gekonsolideer met bestaande radioruis metingsprotokolle en voorspellingsmetodes. Die gebruik van 'n koronakou om opwekkingsfunksies af te lei vir monopolêre radiosteuringvoorspellings is ondersoek en daar is gevind dat 'n klein koronakou nie gebruik kan word om radiosteuringvlakke op hoogspanningsgelykstroom transmissielyne akkuraat te voorspel nie. Dit is as gevolg van die opbou van ruimtelading in die klein elektrodegaping. Met behulp van die sika, numeriese modellering en beide die frekwensie- en tydgebiedmetings, is dit nou moontlik om te verklaar waarom die klein koronakou die akkurate radiosteuringvoorspellings op transmissielyne onmoontlik maak. Die groot buitelug-koronakou en kort toetslyn radiosteuringvoorspellings stem ooreen met bestaande empiriese voorspellings formules.

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De, Medina Dafne Diez. "Constant current electronarcosis of market poultry." Thesis, This resource online, 1993. http://scholar.lib.vt.edu/theses/available/etd-09192009-040444/.

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Van, Rhyn P. D. "High voltage DC-DC converter using a series stacked topology." Thesis, Link to the online version, 2006. http://hdl.handle.net/10019/1269.

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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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Henning, Pieter Hendrik. "Control of a 1.5 MW active power filter and regeneration converter for a Spoornet DC traction substation." Thesis, Stellenbosch : University of Stellenbosch, 2005. http://hdl.handle.net/10019.1/2340.

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Thesis (MScEng (Electrical and Electronic Engineering))--University of Stellenbosch, 2005. Although regenerative braking has been in used in railway systems for a long time already, the energy generated was dissipated in resistor banks. The rapid advances in the power electronics field, accompanied by the development of faster and higher power switching devices in recent years, now make it possible to convert the regenerated electrical energy from DC to AC, which can then be injected into the Eskom grid. A 1.5 MW full scale prototype system was built, installed and tested in a Spoornet DC traction substation. A seven level series-stacked converter topology was used along with a specially designed injection transformer. The system was controlled by the PEC 33 controller board, which was developed at the University of Stellenbosch. The primary function of the system is to function as a regeneration converter and as a secondary function act as an active power filter.

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Eren, Levent. "Bearing damage detection via wavelet packet decomposition of stator current /." free to MU campus, to others for purchase, 2002. http://wwwlib.umi.com/cr/mo/fullcit?p3074397.

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Mushagala, Jimmy Matabaro. "Harmonic analysis and effectiveness of mitigation techniques applied to a bipolar HVDC system." Thesis, Cape Peninsula University of Technology, 2017. http://hdl.handle.net/20.500.11838/2461.

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Thesis (MTech (Electrical Engineering))--Cape Peninsula University of Technology, 2017. High Voltage Direct Current (HVDC) transmission is a safe and efficient technology designed to deliver large amounts of electrical power over long distances with minimal losses and at low costs. HVDC links require converters and filters at both terminal stations. The core component of the HVDC system is the power converter that connects the DC and AC systems together. The conversion from AC to DC, and vice versa, is achieved mainly through electronic switches called thyristors. The thyristor-based Line Commutated Converter (LCC) is a mature and trusted technology for HVDC transmission throughout the world. HVDC converters are bidirectional and can function in either rectification (AC to DC) or inversion mode (DC to AC). This is achieved when the voltage polarity across the converter gets swapped by the controllers, because current cannot change its direction in thyristors. In this thesis an analytical model of the HVDC converters is developed in the frequency domain by modelling it in DIgSILENT. The objective is to study the harmonics induced to the AC side from HVDC converters. Therefore, it is important in the real world to understand the principles, what causes harmonics to be generated in HVDC and transferred to the HVAC system. The objective of this thesis is to investigate the effectiveness of mitigation techniques used, on how they reduce harmonics by keeping these harmonic levels within specified values admissible by international standards (e.g. IEEE, etc).

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Dissertations / Theses on the topic 'Electric current'

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