Tesi sul tema "High voltages in art"
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1
Farag, Bassem. "High Voltage DC Arc Detection Model". Thesis, Uppsala universitet, Institutionen för informationsteknologi, 2018. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-358478.
Testo completoAbstract (sommario):
High voltage (HV) battery systems are widely used in many applications nowadays. And due to the safety concerns regarding lithium-ion cells, the safety of the lithium-ion based battery systems is vital. One crucial danger for lithium-ion cells is heat, And as arcs formation can lead to heat generation within the system, it is important to detect arcs that take place frequently within HV battery systems. This thesis is done in cooperation with Northvolt AB and it focuses on assessing the ability to detect the occurrence of arcs in the system, but it does not focus on preventing arcs.The goal is to build a detection system to identify the occurrence of arcs, both within the battery system and in the connection between the battery system and the load (vehicle). The detection circuit should not affect the ability of the isolation measurement unit inside the system, and the detection system should be protected at all times. The circuit was designed and tested using LTSPice software. This is due to the absence of a ready system to test the circuit against at Northvolt. The system was able to detect arcs both within the battery system and when connecting the battery system to the vehicle. Additionally, as required by Northvolt, the detection system is designed without affecting the isolation measurement unit and the detection system is kept safe at all times by using an isolation circuit. Future work is recommended to generalize the detection system so it can be used in different high voltage applications. This can be done by testing the system against other HV systems and updating the filter and amplifier’s values, as well as the software thresholds. Additionally, it is recommended that the software module is calibrated against the real system during hardware testing. This calibration will optimize the software module and, thus, result in better detection.
2
Gerrard, Carl Andrew. "Remote monitoring of power system conductor voltages". Thesis, University of Liverpool, 1996. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.263990.
Testo completo
3
Islas, Michael E. "Efficiency improvement techniques for high voltage capacitor carging [sic] methods". Orlando, Fla. : University of Central Florida, 2009. http://purl.fcla.edu/fcla/etd/CFE0002899.
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4
Young, Karl Anthony. "Development of a high voltage rotating arc SF₆ interrupter". Thesis, University of Liverpool, 2005. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.428219.
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5
Macfarlane, Douglas James. "Design and fabrication of AlGaN/GaN HEMTs with high breakdown voltages". Thesis, University of Glasgow, 2014. http://theses.gla.ac.uk/4835/.
Testo completoAbstract (sommario):
Gallium nitride based transistors will make up a large portion of the power electronics and the microwave electronics sectors in the very near future, replacing traditional materials such as silicon (Si) and gallium arsenide (GaAs). The work in this thesis focuses on AlGaN/GaN high electron mobility transistors (HEMTs) in particular, with the aim of gaining the maximum potential out of them with regards to breakdown voltage. GaN based devices are able to breakdown at higher voltages compared to Si or GaAs due to its wider band gap (3.4 eV compared to 1.1 eV and 1.4 eV respectively) and although a lot of work has been invested into these devices over the last two decades or so, their full potential has yet to be realised and new solutions are still sought to provide a complete engineering solution which will make them competitive and commercially viable. One of the main obstacles is the high electric fields generated at the drain side of the gate which have prevented these devices from reaching their theoretical breakdown fileld of around 300 V/um. In an attempt to overcome this, several approaches have been investigated in this thesis including metal insulator semiconductor HEMTs (MIS-HEMTs), `gate overlapping' HEMTs, where the gate partially overlaps the source and drain contacts and finally a device employing a Schottky source and a Schottky drain contact. The results given show that a MIS-HEMT can have a substantially larger breakdown voltage compared to a Schottky gate HEMT which is clarified through qualitative simulated electric field work and experimental work. Further, the MIS-HEMT shows a high breakdown field of about 87 V/um when a Schottky drain contact is incorporated. The gate overlapping HEMTs attempts to mitigate completely the large electric field found at the drain edge of the gate. Simulated and experimental results are given for this device concept and reveal that the large electric field peak is indeed removed, however, low breakdown voltages are still incurred due to the closeness of the gate edge to the drain contact. Finally, results are given for a device employing Schottky source and Schottky drain contacts and reveals that present theory may not completely describe the operation of this device.
6
Washabaugh, Andrew Patrick. "Electrokinetic pumping of semi-insulating liquids by traveling wave high voltages". Thesis, Massachusetts Institute of Technology, 1989. http://hdl.handle.net/1721.1/14509.
Testo completoAbstract (sommario):
Thesis (M.S.)--Massachusetts Institute of Technology, Dept. of Electrical Engineering and Computer Science, 1989.Includes bibliographical references (leaves 182-184).
by Andrew Patrick Washabaugh.
M.S.
7
Benwell, Andrew L. Kovaleski Scott D. "A high voltage piezoelectric transformer for active interrogation". Diss., Columbia, Mo. : University of Missouri--Columbia, 2009. http://hdl.handle.net/10355/6847.
Testo completoAbstract (sommario):
Title from PDF of title page (University of Missouri--Columbia, viewed on Feb 23, 2010). The entire thesis text is included in the research.pdf file; the official abstract appears in the short.pdf file; a non-technical public abstract appears in the public.pdf file. Dissertation advisor: Dr. Scott D. Kovaleski. Vita. Includes bibliographical references.
8
Aldawsari, Mohammed. "Partial Discharge Behavior on Power Module with High dv/dt Square Voltages". The Ohio State University, 2019. http://rave.ohiolink.edu/etdc/view?acc_num=osu155563114540074.
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9
Bandaru, Sreekanth. "Effect of high frequency pulse voltages and high temperature on the lifetime characteristics of magnet wires". Master's thesis, Mississippi State : Mississippi State University, 2004. http://library.msstate.edu/etd/show.asp?etd=etd-05132004-135217.
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10
Al-Busaidi, Ahmed Said Obaid. "A generator-set for series hybrid electric vehicles operating at high output voltages". Thesis, University of Newcastle Upon Tyne, 2011. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.556284.
Testo completoAbstract (sommario):
Series hybrid electric vehicles have their wheels driven by an electric motor powered by a battery with an engine plant that cranks a generator unit to provide electric power to the battery and if necessary to the electric motor. They promise significant reductions in greenhouse gases without compromising driving performance. This year GM has launched the first mass produced series hybrid electric vehicle and other car manufacturer are to follow over the next decade. In recent years significant progress has been made in new battery techno logies, electric propulsion designs, and optimisation of power flow and control of the electric components to reduce the weight and cost. While these developments have been made successfully, little attention has been spent on improvement of the generator-set for series hybrid electric vehicles. Generally, a generator-set consists of a three-phase machine and a three-phase rectifier circuit. Conventional generator- sets suffer from significant voltage drops across the output of the rectifier circuit caused by current commutation, resulting from interaction between the machine inductances and the rectifier. Any voltage drop across the output of the rectifier circuit leads to an inefficient operation ofthe generator system. In this thesis, a new generator-set for the use in series hybrid electric vehicle applications is presented, whereby the voltage drop caused by commutation is eliminated. In a typical rectifier circuit the output voltage drop is proportional to the commutation time, which is a function of the value of the machine inductance. The novel topology operates in such a way that the commutation time becomes independent from the value of the machine inductance. This is achieved by eliminating the output de-link capacitors that are used in traditional rectifier circuits and transferring these capacitors within a new rectifier circuit. These embedded capacitors are charged and discharged simultaneously with two switches. The capacitors still have the function of electric storage but they also operate in resonance with the supply inductance.
11
Elayyan, H. S. B. "Protection of high voltage systems against surge voltages : New models and measurement techniques". Thesis, Cardiff University, 1987. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.378453.
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12
Hall, William Bewick. "Reduced energy requirement study for extra high voltage circuit breakers". Thesis, University of Sunderland, 1996. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.268097.
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13
Naredo, V. José Luis A. "Communication frequency response of high voltage power lines". Thesis, University of British Columbia, 1987. http://hdl.handle.net/2429/26725.
Testo completoAbstract (sommario):
Several methods for calculating the electrical phase and modal parameters of overhead transmission lines are described in this thesis; then, a graphical method for evaluating communication frequency response of delta transmission lines -based on the guidelines given by W. H. Senn [12,13,14]- is developed. The graphical method, combined with the parameters calculation methods, obviates the need of large mainframe computers for the analysis of power line carrier (PLC) systems.
A new technique for assessing coupling alternatives, based on Senn's method, is developed. The technique is applied to generate coupling recommendations; it is found that many of the current recommendations given elsewhere [21] are not reliable.
Finally, future work to be done in this field is proposed.Applied Science, Faculty of
Electrical and Computer Engineering, Department of
Graduate
14
Gustavsson, Niklas. "Evaluation and Simulation of Black-box Arc Models for High-Voltage Circuit-Breakers". Thesis, Linköping University, Department of Electrical Engineering, 2004. http://urn.kb.se/resolve?urn=urn:nbn:se:liu:diva-2299.
Testo completoAbstract (sommario):
The task for this Master thesis was to evaluate different black-box arc models for circuit-breakers with the purpose of finding criteria for the breaking ability. A black-box model is a model that requires no knowledge from the user of the underlying physical processes. Black-box arc models have been used in circuit-breaker development for many years. Arc voltages from tests made in the High Power Laboratory in Ludvika were used for validation, along with the resistance calculated at current zero, R0, and 500 ns before current zero, R500.
Three different arc models were evaluated: Cassie-Mayr, KEMA and an arc model based on power calculations. The third model gave very good results and if the model is developed further, the breaking ability could easily be estimated.
The arc model based on power calculations could be improved by using better approximations of the quantities in the model, and by representing the current better. A further suggestion for the following work is to combine the second arc model tested, the KEMA model, with the model based on power calculations in order to estimate the KEMA model parameters.
The R0 and R500 values should also be calculated from more tests, in order to find a clear limit of the breaking ability.
15
Harrye, Yasen Abdullahi. "Modular dual active bridge DC-DC converter for HVDC applications". Thesis, University of Aberdeen, 2017. http://digitool.abdn.ac.uk:80/webclient/DeliveryManager?pid=235762.
Testo completoAbstract (sommario):
The role of high/medium power bidirectional DC-DC converters in the next generation of multi-terminal high voltage DC transmission networks is to enable intercontinental bulk power transfer. This is encouraged by increased DC-DC converter functionalities such as DC voltage stepping/matching, DC line tapping, power flow regulation, bidirectional power flow control, and DC fault isolation. In this work, a bidirectional dual active bridge (DAB) DC-DC converter is selected to pursue such functionalities, due to its desirable features for use in high power applications. This includes galvanic isolation, fast power reversal, high power density, buck/boost operation, possibility of high stepping ratio of conversion and its inherent fault isolation capability without a need for a very fast controller. However, increased reactive power and reduced soft switching range are the main limitations of DAB for applications involving high voltage conversion ratios. Reactive power circulation increases the converter RMS current leading to an increase in conduction losses especially in high power applications. Therefore, a novel triple phase shift (TPS) control algorithm that minimises the total reactive power is proposed to enhance the performance of the DC-DC converter. The algorithm iteratively searches for TPS control variables that satisfy the desired active power flow while selecting the operating mode(s) with minimum reactive power consumption. In addition, a complete DAB converter behaviour under TPS control which has not been studied in the literature before is performed for both power flow directions. Steady state analysis is undertaken for each mode by computing exact expressions for modes power transfer and range (to characterise mode boundary) without fundamental frequency assumption. A new definition of reactive power consumption based on converter total inductance is proposed and a detailed constraint for zero voltage switching (ZVS) is also presented. Moreover, it is shown that all known DAB phase shift modulation techniques including conventional, dual and extended phase shift, represent special cases of TPS, therefore the presented analysis provides a generalised theory for all phase shift based modulation techniques. To scale the converter to higher power level, a modular DAB converter is implemented with a development of power sharing controllers that utilise TPS modulation scheme. The focus is to ensure stable operation of the DAB modules in both power flow directions in the presence parametric mismatches. The reactive power minimisation algorithm and a new DC fault management mechanism are embedded within the proposed controllers. Detailed simulation and experimentation are used to validate the proposed algorithm and power sharing controllers.
16
Bialek, Thomas Owen. "Evaluation and modeling of high-voltage cable insulation using a high-voltage impulse". Diss., Mississippi State : Mississippi State University, 2005. http://library.msstate.edu/content/templates/?a=72.
Testo completo
17
Kapuduwage, Sarath, e skapuduwage@hotmail com. "Fault Location on the High Voltage Series Compensated Power Transmission Networks". RMIT University. Electrical and Computer Engineering, 2007. http://adt.lib.rmit.edu.au/adt/public/adt-VIT20080418.120506.
Testo completoAbstract (sommario):
Nowadays power transmission networks are capable of delivering contracted power from any supplier to any consumer over a large geographic area under market control, and thus transmission lines are incorporated with FACTs series compensated devices to increase the power transfer capability with improvement to system integrity. Conventional fault location methods developed in the past many years are not suitable for FACTs transmission networks. The obvious reason is that FACTs devices in transmission networks introduce non-linearity in the system and hence linear fault detection methods are no longer valid. Therefore, it is still a matter of research to investigate developing new fault detection techniques to cater for modern transmission network configurations and solve implementation issues maintaining required accuracy. This PhD research work is based on developing an accurate and robust new fault location algorithm for series compensated high voltage transmission lines, considering many issues such as transmission line models, configurations with series compensation features. Building on the existing knowledge, a new algorithm has been developed for the estimation of fault location using the time domain approach. In this algorithm, instantaneous fault signals from the transmission line ends are measured and applied to the algorithm to calculate the distance to fault. The new algorithm was tested on two port transmission line model developed using EMTP/ATP software and measured fault data from the simulations are exported to the MATLAB space to run the algorithm. Broad range of faults has been simulated considering various fault cases to test the algorithm and statistical results obtained. It was observed that the accuracy of location of fault on series compensated transmission line using this algorithm is in the range from 99.7 % to 99.9% in 90% of fault cases. In addition, this algorithm was further improved considering many practical issues related to modern series compensated transmission lines (with TCSC var compensators) achieving similar accuracies in the estimation of fault location.
18
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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19
Sobol, О. V., V. A. Stolbovoy, S. V. Aleshin, A. A. Andreev, S. N. Grigorev, V. F. Gorban e M. A. Volosova. "Stucture and mechanical characteristics of vacuum arc TiN coatings deposited with high-voltage high frequency pulses on the substrate". Thesis, Видавництво СумДУ, 2011. http://essuir.sumdu.edu.ua/handle/123456789/20579.
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20
Li, Hayley Han. "Changes in the cation ordering of layered O3 Lix̳Ni₀.₅Mn₀.₅O₂ during electrochemical cycling to high voltages". Thesis, Massachusetts Institute of Technology, 2007. http://hdl.handle.net/1721.1/38706.
Testo completoAbstract (sommario):
Thesis (S.M.)--Massachusetts Institute of Technology, Dept. of Mechanical Engineering, 2007.Pages 124-125 blank. In title on t.p., double-underscored "x" appears as subscript.
Includes bibliographical references (p. 95-98).
Selected area electron diffraction patterns were collected from a pristine LiNi₀.₅Mn₀.₅O₂ sample and cycled Lix̳Ni₀.₅Mn₀.₅O₂ samples to 4.5 V and 5.3 V in the charged and discharged states. In the pristine sample, the single-crystal diffraction patterns clearly revealed superlattice reflections consistent with a ... supercell that is characteristic of cation ordering in the transition metal layer. Furthermore, these superlattice reflections were found to have considerably weakened or completely disappeared in the charged samples. Comparing the 4.5 V and 5.3 V charged samples, fewer crystals in the 5.3 V charged sample were found to exhibit these superlattice reflections. Another difference is that additional superlattice reflections consistent with the 01 phase with hexagonal-close-packed oxygen array were detected in the 5.3 V but not in the 4.5 V charged sample. Therefore, electron diffraction evidence was found to support the concept of Ni migration from the Li to the transition metal layer, and to confirm the increased Ni occupancy in the transition metal layer upon charging. In addition, electron diffraction data showed that Ni migration was in part reversible upon discharge as demonstrated by the increase in the fractions of crystals exhibiting the ... superlattice reflections from the charged to the discharged samples.
(cont.) The excellent electrochemical activity and reversibility of LiNi₀.₅Mn₀.₅O₂ having Ni in the Li layer may be attributed to the mobility of Ni ions upon electrochemical cycling. It has been found that high voltage exposure has resulted in higher discharge capacity and better rate capability. In the cycled samples, a new type of superlattice reflections was observed in addition to the ... superlattice reflections. These superlattice reflections are similar for both the charged and the discharged samples, but their origins were believed to differ. For the charged samples, it was proposed that Li, Ni, and vacancies are partially ordered in the tetrahedral sites in a ... supercell with the space group ... Such ordering may improve the stability of the 03 layered structure upon charging to high voltages. For the discharged samples, Li, Ni, and vacancies order mostly in the octahedral sites in an ... cell with the space group P2/m. It was believed that this arrangement may facilitate Li diffusion in the interlayer slab space upon discharge.
by Hayley Han Li.
S.M.
21
湯世傑 e 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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22
Marsh, Randal Charles. "Evolving Art in Junior High". BYU ScholarsArchive, 2013. https://scholarsarchive.byu.edu/etd/3872.
Testo completoAbstract (sommario):
A junior high teacher and artist altered the curriculum of his Art Foundations II course and his own artistic practice in response to complexity thinking. This teacher-artist-researcher uses the arts-based methodology a/r/tography to make meaning of the relationship between his art and pedagogy. The a/r/tographer explains the impact of complexity on the philosophy of education, a/r/tography as a methodology, and the meaning making that occurred are included. Evolution was used as a methodology for art making and as constraint for developing artworks in the classroom and in the author's own art. The teacher-artist-researcher conceptualizes art as an emergent complex cultural practice that evolves over time. He argues that artists, teachers, consumers, and students are implicated in the evolution of art.
23
Hermosillo, Worley Victor Federico. "Design of The Ohio State University high voltage laboratory". Connect to resource, 1987. http://rave.ohiolink.edu/etdc/view?acc%5Fnum=osu1126811509.
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24
Liu, Miao. "High-voltage-enabled operational amplifier and active-decoupling technique for wideband balun-LNA". Thesis, University of Macau, 2011. http://umaclib3.umac.mo/record=b2550551.
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25
Agjee, F. M. D. E. (Faatima Moosa Dawood Ebrahim). "A wideband signal conditioning system for high voltage measurements using a transconductance topology". Thesis, Stellenbosch : Stellenbosch University, 2000. http://hdl.handle.net/10019.1/51633.
Testo completoAbstract (sommario):
Thesis (MScEng)--Stellenbosch University, 2000.ENGLISH ABSTRACT: Recent research has shown that standard substation capacitive voltage transformers (CVTs) and current transformers (CTs) can be used for the measurement of wideband high voltage phenomena by employing these apparatus in a transconductance topology. With this topology the voltage waveform can be obtained by integration of the ground return current in the earth straps of the CVT and the CT. This technique does, however, impose unique requirements on the amplification and integration instrumentation due to large dynamic range requirements and the strict offset specifications required for accurate integration. This thesis describes a programmable, wideband signal conditioning system for high voltage (HV) measurements using the transconductance topology. A suitable system topology, optimised to reduce the problems usually associated with grounding and electromagnetic interference (EMI) in HV environments, is proposed. This system consists of an analog signal conditioning subsystem, a digital signal conditioning subsystem and a high speed serial fibre-optic link. The analog signal conditioning subsystem conditions the signals from a sensor to levels suitable for the digitiser of the digital signal conditioning subsystem. The high bandwidth specification of the application made it necessary to consider both discrete and integrated implementation of the analog signal conditioning subsystem. Based on the simulated and laboratory test results of both implementations, the optimum design was chosen for the developed system. The digital signal conditioning subsystem, which performs the integration, as well as the serial optic-fibre link control logic was implemented using programmable logic array (PLA) technology. The digital data is transmitted across the fibre-optic link. This data is then converted back to an analog signal. Keywords: High voltage measurements, Transconductance topology.
AFRIKAANSE OPSOMMING: Onlangse navorsing het aangetoon dat standaard substasie kapasitiewe spanningstransformators en stroomtransformators gebruik kan word om wyeband hoogspanningsverskynsels te meet deur hierdie apparatuur in 'n transkonduktansie topologie aan te wend. Met hierdie topologie kan die spanningsgolfvorm verkry word deur die integrasie van die aardstrome in die aardverbindings van die kapasitiewe spanningstransformators en stroomtransformators. Hierdie tegniek stel egter unieke vereistes vir die versterkings- en integrasieinstrumentasie te wyte aan groot dinamiese bereik vereistes en die streng afset spesifikasies wat benodig word vir akkurate integrasie. Hierdie tesis beskryf 'n programmeerbare, wyeband seinkondisioneringstelsel vir hoogspanningsmetings deur van die transkonduktansie topologie gebruik te maak. 'n Geskikte stelseltopologie, wat geoptimiseer is om probleme, wat gewoonlik met aarding en elektromagnetiese interferensie in hoogspanningsomgewings geassosieer word, te verminder, is voorgestel. Die stelsel bestaan uit 'n analoog seinkondisioneringsubstelsel, 'n digitale seinkondisioneringsubstelsel en 'n hoëspoed seriële optiese vesel koppelvlak. Die analoog seinkondisioneringsubstelsel kondisioneer die seine vanaf 'n sensor na geskikte vlakke vir die versyferaar van die digitale seinkondisioneringsubstelsel. Die hoë bandwydte spesifikasie van die toepassing vereis die inagneming van beide diskrete en geïntegreerde implementerings van die analoog seinkondisioneringsubstelsel. Gebaseer op gesimuleerde en laboratorium toetsresultate van beide implementerings is die optimale ontwerp vir die ontwikkelde stelsel gekies. Die digitale seinkondisioneringsubstelsel wat die integrasie uitvoer, asook die seriële optiese vesel koppelvlak beheerlogika is geïmplementeer met behulp van programmeerbare logika skikking tegnologie. Die digitale data word gestuur oor die optiese vesel koppelvlak. Hierdie data word dan terug geskakel na 'n analoog sein. Sleutelwoorde: Hoogspanningsmetings, Transkonduktansie topologie.
26
Albertson, Rebekah Ann. "Art and identity: the high school artist". Thesis, University of Iowa, 2011. https://ir.uiowa.edu/etd/2667.
Testo completoAbstract (sommario):
The purpose of this study is to investigate the artistic identity of high school females and the relationships they have with their art teachers. The research compiled my own experience as a high school student with the reflections of five participants who graduated from high school within the past five years. Each participant was interviewed about her time in high school related to art, including relationships and events in and outside of the art classroom. The themes that emerged from each participant's experience brought about the conclusion that the high school artistic identity is comprised of action, product, space, and perception. Uncovering the artistic identity of the high school student highlights the importance of the art teacher and the physical and emotional space they create in the art room.
27
Adabi, Firouzjaee Jafar. "Remediation strategies of shaft and common mode voltages in adjustable speed drive systems". Thesis, Queensland University of Technology, 2010. https://eprints.qut.edu.au/39293/1/Jafar_Adabi_Firouzjaeel_Thesis.pdf.
Testo completoAbstract (sommario):
AC motors are largely used in a wide range of modern systems, from household appliances to automated industry applications such as: ventilations systems, fans, pumps, conveyors and machine tool drives. Inverters are widely used in industrial and commercial applications due to the growing need for speed control in ASD systems. Fast switching transients and the common mode voltage, in interaction with parasitic capacitive couplings, may cause many unwanted problems in the ASD applications. These include shaft voltage and leakage currents.
One of the inherent characteristics of Pulse Width Modulation (PWM) techniques is the generation of the common mode voltage, which is defined as the voltage between the electrical neutral of the inverter output and the ground. Shaft voltage can cause bearing currents when it exceeds the amount of breakdown voltage level of the thin lubricant film between the inner and outer rings of the bearing. This phenomenon is the main reason for early bearing failures.
A rapid development in power switches technology has lead to a drastic decrement of switching rise and fall times. Because there is considerable capacitance between the stator windings and the frame, there can be a significant capacitive current (ground current escaping to earth through stray capacitors inside a motor) if the common mode voltage has high frequency components. This current leads to noises and Electromagnetic Interferences (EMI) issues in motor drive systems.
These problems have been dealt with using a variety of methods which have been reported in the literature. However, cost and maintenance issues have prevented these methods from being widely accepted. Extra cost or rating of the inverter switches is usually the price to pay for such approaches. Thus, the determination of cost-effective techniques for shaft and common mode voltage reduction in ASD systems, with the focus on the first step of the design process, is the targeted scope of this thesis. An introduction to this research – including a description of the research problem, the literature review and an account of the research progress linking the research papers – is presented in Chapter 1.
Electrical power generation from renewable energy sources, such as wind energy systems, has become a crucial issue because of environmental problems and a predicted future shortage of traditional energy sources. Thus, Chapter 2 focuses on the shaft voltage analysis of stator-fed induction generators (IG) and Doubly Fed Induction Generators DFIGs in wind turbine applications. This shaft voltage analysis includes: topologies, high frequency modelling, calculation and mitigation techniques. A back-to-back AC-DC-AC converter is investigated in terms of shaft voltage generation in a DFIG. Different topologies of LC filter placement are analysed in an effort to eliminate the shaft voltage.
Different capacitive couplings exist in the motor/generator structure and any change in design parameters affects the capacitive couplings. Thus, an appropriate design for AC motors should lead to the smallest possible shaft voltage. Calculation of the shaft voltage based on different capacitive couplings, and an investigation of the effects of different design parameters are discussed in Chapter 3. This is achieved through 2-D and 3-D finite element simulation and experimental analysis.
End-winding parameters of the motor are also effective factors in the calculation of the shaft voltage and have not been taken into account in previous reported studies. Calculation of the end-winding capacitances is rather complex because of the diversity of end winding shapes and the complexity of their geometry. A comprehensive analysis of these capacitances has been carried out with 3-D finite element simulations and experimental studies to determine their effective design parameters. These are documented in Chapter 4. Results of this analysis show that, by choosing appropriate design parameters, it is possible to decrease the shaft voltage and resultant bearing current in the primary stage of generator/motor design without using any additional active and passive filter-based techniques.
The common mode voltage is defined by a switching pattern and, by using the appropriate pattern; the common mode voltage level can be controlled. Therefore, any PWM pattern which eliminates or minimizes the common mode voltage will be an effective shaft voltage reduction technique. Thus, common mode voltage reduction of a three-phase AC motor supplied with a single-phase diode rectifier is the focus of Chapter 5. The proposed strategy is mainly based on proper utilization of the zero vectors.
Multilevel inverters are also used in ASD systems which have more voltage levels and switching states, and can provide more possibilities to reduce common mode voltage. A description of common mode voltage of multilevel inverters is investigated in Chapter 6.
Chapter 7 investigates the elimination techniques of the shaft voltage in a DFIG based on the methods presented in the literature by the use of simulation results. However, it could be shown that every solution to reduce the shaft voltage in DFIG systems has its own characteristics, and these have to be taken into account in determining the most effective strategy.
Calculation of the capacitive coupling and electric fields between the outer and inner races and the balls at different motor speeds in symmetrical and asymmetrical shaft and balls positions is discussed in Chapter 8. The analysis is carried out using finite element simulations to determine the conditions which will increase the probability of high rates of bearing failure due to current discharges through the balls and races.
28
Abraham, Berhane Teclesenbet. "Degradation and recovery of polydimethylsiloxane (PDMS) based composites used as high voltage insulators". Thesis, Stellenbosch : Stellenbosch University, 2004. http://hdl.handle.net/10019.1/49902.
Testo completoAbstract (sommario):
Thesis (MSc)--Stellenbosch University, 2004.ENGLISH ABSTRACT: Polydimethylsiloxane (PDMS) compounds are utilized in outdoor high voltage insulation due to their low weight, vandalism resistance, better anti-contamination performance and their superior hydrophobic nature. Under severe environmental conditions and over prolonged service time, however, the hydrophobic surface can gradually become hydrophilic and then recover with adequate resting period. In this study, room temperature vulcanized (RTV) PDMS samples were prepared with different formulations and then exposed to corona discharge to evaluate its effect. The influence of different additives, such as different types and amount of fillers and additionally added low molar mass silicone oils, on the hydrophobicity recovery of the material was investigated. The effects of two types of corona treatment were also evaluated. Hydrophobicity recovery of corona and UV-C aged PDMS samples was evaluated by means of static contact angle measurements. Positron annihilation spectroscopy (PAS) gave important information on the micro structural change after corona treatment of RTV PDMS as well as naturally aged high temperature vulcanized (HTV) PDMS samples. The different formulations of the RTV PDMS samples and the effect of the additives were studied with this technique. The formation of a thin, highly crosslinked inorganic silica-like (SiOx) layer was confirmed even at the early stage of degradation. It was also possible to estimate the thickness of the silica-like layer formed during corona exposure that is responsible for the loss and recovery of hydrophobicity. The surface hardness and hydrophilicity change of PDMS samples due to corona treatment were studied simultaneously with force distance measurements by atomic force microscopy (AFM). The adhesive force calculated from the pull-off force-distance curves showed that the adhesive force between the probe and the sample decreased with increasing corona treatment time, indicating hydrophobicity recovery. In addition to this, the increase in hardness after corona exposure provides indirect evidence of the formation of a silica-like layer. In all cases the hydrophilicity and the surface hardness of the PDMS samples increased directly after corona treatment and recovered with time. Two types of FTIR spectroscopy were used to analyse the surface of the polymer.
AFRIKAANSE OPSOMMINGS: Polidimetielsiloksaan (PDMS) word in buitelug hoogspanninginsulasie gebruik as gevolg van sy lae massa, weerstand teen vandalisme, verbeterde anti-kontaminasie werkverrigting en superieure hidrofobiese karakter. Die hidrofobiese oppervlakte kan egter gelydelik hidrofillies word onder uiterste omgewingsomstandighede en oor langdurige dienstyd. PDMS materiaal herstel egter nadat dit genoeg rustyd toegelaat is. Kamertemperatuur-gevulkaniseerde (KTV) PDMS met verskillende formulasies is in hierdie studie voorberei, aan korona ontlading blootgestel, geëvalueer en vergelyk. Die invloed van bymiddels soos verskillende tipes en hoeveelhede vuiler, asook addisionele lae molekulêre massa silikoonolie, op die herstel van hidrofobisiteit van die materiaal is ondersoek. Twee verskillende metodes van korona behandeling is ook geëvalueer. Die herstel van hidrofobisiteit van korona en UV-C verouderde PDMS monsters is met statiese kontakhoekmeting geëvalueer. Positronvernietigingspektroskopie (PVS) is 'n kragtige tegniek wat belangrike inligting oor die mikrostrukturele verandering van korona behandelde van KTV PDMS sowel as natuurlik-verouderde hoë temperatuur gevulkaniseerde (HTV) PDMS monsters gee. Die verskillende formulasies van die KTV PDMS monsters, sowel as die effek van die vullers, is met behulp van hierdie tegniek ondersoek. Die vorming van 'n dun, hoogskruisgebinde, anorganiese silika-agtige (SiOx) laag op die PDMS oppervlak, selfs tydens die vroeë stadium van degradasie, is bevestig. Dit was ook moontlik om die dikte van die silika-agtige laag wat gedurende die korona blootstelling gevorm het, en wat verantwoordelik is vir die verlies aan hidrofobisiteit, te bepaal. Die oppervlakhardheid en hidrofilisiteit verandering van PDMS monsters as gevolg van korona behandeling, was gelyktydig met krag-afstand metings deur middel van atoomkragmikroskopie (AKM) bestudeer. Die kleefkrag, soos bereken van aftrek kragafstandkurwes, dui daarop dat kleefkragte tussen die taster en die monster afneem met toenemende korona behandelingstyd, wat beduidend is op die herstel van hidrofobisiteit. Daarbenewens is die toename van oppervlakhardheid na korona blootstelling "n indirekte bewys van die formasie van 'n silika-agtige laag. In alle gevalle het die hidrofilisiteit en die oppervlakhardheid van die PDMS monsters toegeneem direk na afloop van korona behandeling en gevolglik herstel met tyd. Twee tipes IR spektroskopie metodes is gebruik vir die chemiese-oppervlak analises
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Farr, Ewan Mark. "Modelling, control and implementation of the alternate arm converter (AAC) : a new topology for high voltage direct current (HVDC) applications". Thesis, University of Nottingham, 2016. https://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.718463.
Testo completoAbstract (sommario):
Conventional electricity generation, transmission and distribution infrastructures are AC systems, which combine to form an AC grid. Supply security can be increased by interconnecting AC grids. Additionally, there is an increasing reliance on remote asyn-chronous distributed generation from bulk renewable energy sources. High Voltage Direct Current (HVDC) systems allow asynchronous AC networks to be connected, and are able to transmit bulk power over longer distances with a lower total cost-than High Voltage Alternating Current (HVAC) transmission, or are perhaps the only option. At both ends of a HVDC link, a converter station is required to convert from AC to DC, or vice versa. Originally, these converters were Current Source Converters (CSCs), and later two- or three-level Voltage Source Converters (VSCs).
30
Li, Ting. "Art Center". Thesis, Virginia Tech, 2015. http://hdl.handle.net/10919/53954.
Testo completoAbstract (sommario):
For any artist, imagination is a powerful and necessary instrument for everyday creation. It is like a magical engine that drives the artist forward. But what is imagination? How do we keep this engine running nonstop?
According to the Italian philosopher Giovan Battista Vico, imagination is nothing but extended or compounded memory, imagination is nothing but the springing up of reminiscences, and ingenuity or invention is nothing but the working over of what is remembered.So we can easily understand that people create or invent things out of what they have seen, what they have experienced, and what they have engaged with their own bodies.
In my thesis, I'm not competing with the artists in imagination or creation, but I'm trying to offer them this architectural environment that would be transfigured into memory through senses. The artists living and working in this tower building are encouraged to move vertically through stairways and vertically aligned public spaces. By engaging the body and senses in this vertical movement, the artists would find their way out of the urban canyon to the sky of imagination. They would also be able to live lightly above the bustling world of reality.Master of Architecture
31
Privé, Michel. "Approches physiques et numérique du phénomène des vibrations induites par effet de couronne /". Thèse, Chicoutimi : Université du Québec à Chicoutimi, 1986. http://theses.uqac.ca.
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Keays, William G. (William George) 1960. "Using high-bandwidth input/output in interactive art". Thesis, Massachusetts Institute of Technology, 1999. http://hdl.handle.net/1721.1/61839.
Testo completoAbstract (sommario):
Thesis (S.M.)--Massachusetts Institute of Technology, Program in Media Arts & Sciences, 1999.Includes bibliographical references (leaves 75-78).
Are we making the best use of commonly available high-bandwidth input/output ( I/O) devices on our computers? How would research on this subject be affected if it were driven by a purely artistic mandate? The bandwidth in question refers specifically to video input and output devices, the only high-bandwidth devices that are on found on common, conventional computers. Under normal circumstances, these devices transmit moving two dimensional images at rapid refresh rates; this high-bandwidth is a prerequisite for the capturing and viewing of motion images. A great potential exists in using this high-throughput capacity in applications that do not simply convey continuous moving images. In the burgeoning field of highly technological interactive art, a large number of works suffer from poorly adapted interface mechanisms. New high-bandwidth I/O configurations can serve to derive improved interfaces for the creation of interactive art. This course of research is not driven solely by the desire to create new technology and improved modes of interaction. As the the infusion of rapid-changing technology in art reaches popular levels, the role of the artist in society is equally in flux. The definition of such a role is sought as part of this thesis. These goals are accomplished through the study of the nature and history of interactivity in art, the development of new prototypes, the creation and exhibition of interactive art works in public spaces, and through a close analysis of the role of the artist-scientist in contemporary society.
b William G. Keays.
S.M.
33
Kitching, Dornehl. "Experiences of novice art teachers in high schools". Thesis, Cape Peninsula University of Technology, 2017. http://hdl.handle.net/20.500.11838/2515.
Testo completoAbstract (sommario):
Thesis (MEd)--Cape Peninsula University of Technology, 2017.The teaching profession is unique in this sense that in no other employment industry, are beginner employees straight out of university expected to do the work and hold the responsibilities equal to that of a senior or more experienced colleague. This idea is held as one of the main reasons why teachers need support in their first few years of teaching (Darling-Hammond, 2010; Le Maistre & Paré, 2010). From my own experience as well as that of the novice art teacher participants in this research, it was clear that art teachers in their first three years of teaching experience positive encounters as well as several challenges. Challenges varied from the lack of support and orientation from school management to several other factors that contributed to a demanding workload and stress. The theoretical framework that informs this research is grounded in the combination of theoretical perspectives developed by Geert Kelchtermans (1993; 1994; 1999) namely the narrative-biographical perspective and the micro-political perspective. Participants were interviewed and requested to attend a focus group session where they were asked to create a River of Life representation of their experiences since starting their art education careers. The transcripts were analysed in conjunction with the drawings to forge connections between the participants’ feedback to establish themes. The themes of this particular research relate mainly to the common experiences that the participants face as novice art teachers and the support they receive from their school management and education authorities.
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Henson-Dacey, Jacqueline B. "High School Visual Art Students' Perceptions of Creativity". ScholarWorks, 2015. https://scholarworks.waldenu.edu/dissertations/1406.
Testo completoAbstract (sommario):
When high school art teachers do not understand how their students experience creativity, studio art programs are less effective in fostering student learning than they would otherwise be. Nevertheless, extant research does not reveal a consistent or comprehensive understanding of how adolescents experience creativity in art education. Drawing on Csikszentmihalyi's theory of creativity and flow, this study explored students' perceptions of creativity and its relationship to flow, or the state of consciousness associated with optimal pleasure. This phenomenological study investigated students' perceptions of creativity and flow by interviewing nine high school advanced placement students in a public high school in southwest Florida. Data were drawn from three structured interviews with each subject and a field journal kept by the researcher. The Think Aloud technique used for the second interview provided rich descriptions while participants were in the midst of doing art. Field journal entries were organized according to Bailey's guide to field note classification. Moustakas's interpretation and modifications of the Van Kaam method of analysis provided a systematic approach to transcript reduction. The results of the investigation revealed four themes in the ways students perceive their own creativity, namely, influences, mindset, self-efficacy, and emotions. As they reflected on their perceptions of creativity and flow, students gained a greater awareness of their experience while creating art. Among the study's implications for social change, as art educators elicit these understandings, they foster creativity and transform students' lives in school and potentially, the wider society.
35
Barry, Marie Porterfield. "Lesson 09: Michelangelo- From High Renaissance to Mannerism". Digital Commons @ East Tennessee State University, 2020. https://dc.etsu.edu/art-appreciation-oer/10.
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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.
Testo completoAbstract (sommario):
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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Alvarez, Azalea Aluija. "The effects of an augmented art curriculum on the attitudes of high school art students toward diversity in art". FIU Digital Commons, 1995. http://digitalcommons.fiu.edu/etd/1118.
Testo completoAbstract (sommario):
The purpose of this study was to investigate the effects of an augmented art curriculum on high school art students to determine if those receiving it had more positive attitudes toward diversity in art and used diversity in their art more than students receiving traditional instruction. This study was conducted in a South Florida public high school, with beginning art students. Using a posttest-only control group design and ANOVA (a = .05), it was found that students (n = 54) receiving an augmented art curriculum did not have significantly higher scores on the Attitudes About Art questionnaire than students (n = 57) receiving traditional instruction F (1, 91) =.00, p > .05. However, using the Checklist of Cultural References in Student Art to evaluate student work it was found that there was a significant teacher effect F (1, 30) = 14.14, p
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Bergh, Amy. "TO THE AGES OF AGES: RECONCEPTUALIZING HIGH SCHOOL ART HISTORY CURRICULUM". VCU Scholars Compass, 2011. http://scholarscompass.vcu.edu/etd/2434.
Testo completoAbstract (sommario):
Through this curriculum study, I explored the application of ideas found within contemporary art education to a course of traditional secondary art history. These contemporary art education ideas included: visual culture instruction, interdisciplinary instruction, contemporary art instruction, curriculum development, the use of enduring ideas, and the inclusion of a variety of perspectives based on gender and ethnicity. Through these art education ideas, a new curriculum was formed, that pushed both the students and the teacher toward a more inclusive art history course that made real connections for students and allowed students to be active members in their own learning. Instruction shifted away from lecture and became more dialogue and discussion oriented. Unit examples are included for Romanticism, Dadaism, and American Social Realism.
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Sperandio, Giuliano Salomão. "Fonte CA ressonante de alta tensão para ozonizadores". [s.n.], 2007. http://repositorio.unicamp.br/jspui/handle/REPOSIP/259298.
Testo completoAbstract (sommario):
Orientador: Jose Antenor PomilioDissertação (mestrado) - Universidade Estadual de Campinas, Faculdade de Engenharia Eletrica e de Computação
Made available in DSpace on 2018-08-11T05:49:41Z (GMT). No. of bitstreams: 1 Sperandio_GiulianoSalomao_M.pdf: 1492429 bytes, checksum: f30c57d63ec881417a2d7f6ebaf926c2 (MD5) Previous issue date: 2007
Resumo: O ozônio se apresenta como um excelente produto químico para ser usado em substituição ou em conjunto com o cloro para o tratamento de água. O ozônio é um potente bactericida e viricida e não deixa resíduos no meio ambiente. A produção deve ser local e requer apenas ar e eletricidade. Um método simples e eficaz para a produção de ozônio é através de microdescargas em barreiras dielétricas em oxigênio. A produção da microdescarga é feita numa célula onde é aplicada uma alta tensão, da ordem de quilovolts. A alta tensão é gerada através de um circuito eletrônico de alto rendimento e interage com a carga para produzir a alta tensão desejada. A fonte de alta tensão foi projetada para fazer o uso das não idealidades do conjunto formado pelo transformador de alta tensão associado a célula ozonizadora. O comportamento da carga permite que a potência de saída seja ajustada pela freqüência de trabalho. A potência de saída é uma variável que está associada com a produção de ozônio a qual pode ser ajustada. O controle da potência foi realizado por um microcontrolador que também incorpora funções de proteção e comando remoto. Os resultados obtidos pela implementação prática do circuito eletrônico corroboram o modelo e as simulações feitas. O circuito foi desenvolvido por uma demanda da indÚstria. A etapa de desenvolvimento do circuito em laboratório atingiu uma maturidade satisfatória para industrialização
Abstract: The ozone gas is a powerful oxidizing substance and it can be used for the treatment of water. It is known to be a potent bactericide and viricide and leaves no harmful residues to the environment. Ozone has to be produced on-site and requires only air and eletricity. An efficient way to produce ozone is through diclectric-barrier discharge in oxigen. An electronic high-efficiency circuit is used to generate the necessary high- voltage to make the electric discharge. The circuit was designed to use the resonance of the transformer plus the silent-discharge ozone-generator tube. The transformer non-idealities are usefull for allowing the converter operation in the resonance region, minimizing the commutation losses. The output power can be adjusted setting the switching frequency. The circuit works properly and the practical results match to the simulations. This converter was developed according to the specification of an industry and it is now going into commercial production
Mestrado
Energia Eletrica
Mestre em Engenharia Elétrica
40
Nichols, Athena Irene. "Examining the Role of Active Student Engagement in High School Arts Courses". ScholarWorks, 2015. https://scholarworks.waldenu.edu/dissertations/187.
Testo completoAbstract (sommario):
A primary challenge to educators is the design and implementation of effective student engagement processes. High school students cannot be successful if they are frequently absent from school, as active engagement opportunities reinforce knowledge and help to keep students enthused in their learning. To address the challenges of frequent school absences, this study examined a gap in the literature--namely, the relationship between active engagement and arts courses as a motivator for students to remain in high school. For this study, active engagement was defined as a process in which the student's interests, efforts, and knowledge culminated in an application of the learning content. Using Csikszentmihalyi's (1990) flow theory, a mixed-methods study was conducted to examine students' experiences with active engagement in arts courses. Data were collected from a survey (50 = x) and phenomenological interviews (8 = x). Quantitative analyses of these data included a paired-sample t test to determine whether there was a significant difference between the average values of students' perceived learning capabilities and expectations for learning in relation to arts courses versus non-arts courses. Content analyses created categories and identified themes that found students felt more engaged, self-confident, and motivated about their learning during arts educational experiences. Contributions to positive social change included increased awareness about how students make meaning of active engagement in arts courses. Such information can help school districts understand more about the importance of providing students with artistic and creative educational experiences.
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Watkins, Dawn Elizabeth. "The protection of high art in a postmodern age". Thesis, University of Leicester, 2001. http://hdl.handle.net/2381/31080.
Testo completoAbstract (sommario):
This project considers whether it is possible to define some works of literary or visual art as high art solely by virtue of their inherent qualities, or whether there are factors external to the work which are significant to this process of categorisation. Thereafter the project considers whether it is appropriate to argue that high art as a discrete category should be accorded a value of its own to be defended by the legal system alongside or in preference to other values (particularly freedom of speech), focusing initially upon non-legal arguments which have been put forward in this regard. Thereafter, the project critically analyses the way in which the English legal system has dealt with such issues during the period 1780 to date firstly by analysing the approach of the legislature towards the notion of high art and its protection and secondly, by analysing the approach of the courts in this area. Both the courts' role in enforcing statute law and administering the common law are assessed and the extent to which the courts have acknowledged the free speech principle in relation to artistic and non-artistic matter is given particular consideration. Finally, the project considers those international obligations which influence English law in this area, with particular reference to the European Convention on Human Rights and to the recent inclusion of Article 10, the right to freedom of expression, in the Human Rights Act 1998. The extent to which high art might be afforded greater protection under this new Act is considered, and conclusions are drawn as to whether greater protection should be sought for high art under English law and if so, upon what basis.
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Caldwell, Andrew E. "Daylighting and exhibition at the High Museum of Art". Thesis, Georgia Institute of Technology, 1985. http://hdl.handle.net/1853/23971.
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Beck, Riley D. "High Voltage Analog Design in a Standard Digital CMOS Process". Diss., CLICK HERE for online access, 2005. http://contentdm.lib.byu.edu/ETD/image/etd1092.pdf.
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Vosloo, Wallace L. (Wallace Lockwood). "A comparison of the performance of high-voltage insulator materials in a severely polluted coastal environment". Thesis, Stellenbosch : Stellenbosch University, 2002. http://hdl.handle.net/10019.1/52625.
Testo completoAbstract (sommario):
Thesis (PhD)--University of Stellenbosch, 2002.ENGLISH ABSTRACT: The main aim of this research programme was to compare the relative performance of different insulator materials used in South Africa when subjected to a severe marine pollution environment. A test programme and procedure, test facility and instrumentation were established. Some novel instrumentation and monitoring equipment were developed and built specifically for this research programme, supported by data analysing software programs. In order to compare material performance only, all non-material design variables between the test insulators had to be removed (e.g. creepage distance, connecting length, inter-shed spacing, profile, etc.). To achieve this some of the test insulators had to be specially manufactured. Leakage current, electrical discharge activity, climatic and environmental data was collected successfully over a one-year test period, starting with new test insulators. The peak and energy values of the leakage current were identified as the two main parameters needed to describe the leakage current activity on the test insulators. A correlation was found between the climatic and environmental data and the leakage current data, and it was found that the leakage current can be determined successfully from some of the climatic and environmental parameters monitored by using multiple regression techniques. Surface conductivity and energy were found to be the best parameters to show the maximum and continuous interaction of the insulator material surface with the electrolytic pollution layer. A natural ageing and pollution test procedure was developed, which has become a South African standard and is gaining international acceptance. A model and hypothesis are proposed to describe the electrical discharge activity that takes place on the test insulators and explain the difference in leakage current performance of the various materials. Keywords: Insulator, Pollution, High Voltage, Leakage current, Material performance.
AFRIKAANSE OPSOMMING: Die hoofdoel van hierdie navorsingsprogram was om die relatiewe prestasie van verskillende isolatormateriale wat in Suid-Afrika gebruik word te vergelyk in 'n swaar besoedelde marine omgewing. 'n Toetsprogram en prosedure, toets fasiliteit en instrumentasie is gevestig. 'n Paar nuwe instrumente en moniteer toerusting is ontwikkel en gebou spesifiek vir hierdie navorsingsprogram, gesteun deur data analise sagteware programme. Ten einde slegs materiaalprestasie te vergelyk, moes alle nie-materiaal ontwerpsveranderlikes tussen die toetsisolators verwyder word (bv. kruipafstand, konnekteer lengte, tussen-skerm spasiëring, profiel, ens.). Om dit reg te kry moes sommige van die toetsisolators spesiaal vervaardig word. Lekstroom, elektriese ontladingsaktiwiteit, klimaat en omgewingsdata is suksesvol versameloor 'n een-jaar toetsperiode, beginnende met nuwe toets isolators. Die piek en energie waardes van die lekstroom is identifiseer as die twee hoof parameters wat nodig is om die lekstroomaktiwiteit op die toetsisolators te beskryf. 'n Korrelasie is gevind tussen die klimaat- en omgewingsdata en die lekstroom data, en dit is gevind dat die lekstroom data suksesvol bepaal kan word van sekere van die klimaat- en omgewingsparameters wat gemoniteer is deur veelvoudige regressie tegnieke te gebruik. Oppervlakskonduktiwiteit en energie is gevind die beste parameters te wees om die maksimum en kontinue interaksie van die isolatormateriaaloppervlak met die elektrolitiese besoedelingslaag aan te toon. 'n Natuurlike veroudering en besoedeling toetsprosedure is ontwikkel, wat 'n Suid-Afrikaanse standaard geword het en besig is om internastionale aanvaarding te wen. 'n Model en hipotese word voorgestelom die elektriese ontladingsaktiwiteit wat op die toetsisolators plaasvind te beskryf en om die verskil in lekstroomprestasie van die verskeie materiale te verduidelik. S/eufelwoorde: Isolator, Besoedeling, Hoog Spanning, Leek stroom, Materiaal prestasie.
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Lee, Hyun Min. "French art songs for high voice by famous opera composers". College Park, Md. : University of Maryland, 2005. http://hdl.handle.net/1903/3198.
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Teague, Barbara A. (Barbara Ann). "An Assessment of Arkansas Middle school/Junior High School Art Programs Using National Art Education Association Standards". Thesis, North Texas State University, 1986. https://digital.library.unt.edu/ark:/67531/metadc331828/.
Testo completoAbstract (sommario):
The purpose of the study was to make an assessment of Arkansas middle school/junior high art programs using National Art Education Association standards. Data were collected from questionnaires, curriculum guides, and school visitations. Participating in the study were 127 schools enrolling 53,502 students of which 14,755 (28%) were taking art classes. For comparisons, the state was divided into five regions.
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Luposchainsky, Simon Felix. "Mechanically programmed Fluidic Microactuators for soft robotics applications". Thesis, Queensland University of Technology, 2021. https://eprints.qut.edu.au/213221/1/Simon%20Felix_Luposchainsky_Thesis.pdf.
Testo completoAbstract (sommario):
This thesis covers two projects that connect the engineering field of robotics with the additive manufacturing of microfibre structures by melt electrowriting (MEW). One project utilizes MEW to manufacture soft robots and investigates their function, the second project uses a robotic arm to expand the capabilities of MEW for the creation of better implants in tissue engineering. Both projects result in novel applications and design space for MEW by allowing more complex geometries to be produced and enabling the processing or integration of otherwise inaccessible materials as well as expanding the use cases of the produced constructs beyond static scaffolds.
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Ravishankar, B. R. "Modelling Of Current-Zero Behaviour Of An SF6 Rotating Arc". Thesis, 1997. https://etd.iisc.ac.in/handle/2005/1819.
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Ravishankar, B. R. "Modelling Of Current-Zero Behaviour Of An SF6 Rotating Arc". Thesis, 1997. http://etd.iisc.ernet.in/handle/2005/1819.
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West, Nicholas John. "Investigation into laser triggering of high voltages". Thesis, 2006. http://hdl.handle.net/10539/276.
Testo completoAbstract (sommario):
Master of Science in Engineering - EngineeringIn this thesis, laser-triggering of spark gaps was investigated. In other words, the purpose of the project, was to ascertain what type of laser (in terms of wavelength, energy and pulse width) is the most efficient to accomplish elec-trical breakdown across a short spark gap. The spark gap used was set up in a coaxial geometry and the gap length was able to vary from 20 mm to 2.5 mm or less. Two lasers were used: A KrF excimer (248 nm - UV) and an Nd:YAG (1064-532-355 nm). Experiments showed that a gap of 5 mm in air and a focusing lens of 100 mm, yielded the best (widest) voltage breakdown range. It was found that the key element that will ensure electrical breakdown in a spark gap, was power density (W/cm2). A power density of about 10 GW/cm2 is needed to create a spark in air. In the case of the KrF laser, the voltage range was found to be 2-13 kV (216 mJ/pulse). In the case of the YAG laser operating at 1064 nm (170 mJ/pulse), the range was 600 V-13 kV and for 532 nm (40 mJ/pulse), 3 kV-13 kV. The wavelength of the laser did effect the result. For 1064 nm, breakdown in air occured at 70 mJ, whereas at 532 nm, breakdown occured at 40 mJ. For the case where the SF6 gap was used, the range was found to be much larger than in the case of air. This can be attributed to the sensitivity of this gas to high intensity electric fields.